http://air.eng.ui.ac.id/api.php?action=feedcontributions&user=Alesdaniel&feedformat=atomccitonlinewiki - User contributions [en]2022-05-26T01:48:01ZUser contributionsMediaWiki 1.30.0http://air.eng.ui.ac.id/index.php?title=Ales_Daniel&diff=58641Ales Daniel2021-11-10T03:12:24Z<p>Alesdaniel: </p>
<hr />
<div>NAMA : ALES DANIEL<br />
<br />
TEMPAT, TANGGAL LAHIR : JAKARTA, 27 OKTOBER 1998<br />
<br />
NPM : 1706036072<br />
<br />
DOSEN :<br />
<br />
Dr. Ir. Ahmad Indra Siswantara<br />
<br />
Dr. Eng. Radon Dhelika, B.Eng, M.Eng<br />
<br />
<br />
== Rabu, 4 September 2019 ==<br />
'''Mengapa Saya Harus Belajar Kalkulus?'''<br />
<br />
Kalkulus merupakan suatu ilmu mendasar bagi mahasiswa teknik sebagai bekal untuk melakukan perhitungan pada mata kuliah lainnya. Penggunaan ilmu tersebut dapat mengatasi permasalahan melalui perhitungan berdasarkan data yang diinformasikan. Ilmu Kalkulus lebih berfokus kepada perhitungan fungsi, turunan, integral, dan lain-lain. Pada pertemuan pertama, kami membahas salah satu penggunaan ilmu Kalkulus pada salah satu mata kuliah teknik mesin, Termodinamika. Contoh yang digunakan adalah rumus entalpi sebagai berikut :<br />
<br />
H = U + PV<br />
<br />
Apabila dikaitkan dengan ilmu Kalkulus, rumus tersebut dapat diturunkan menjadi rumus sebagai berikut :<br />
<br />
dH = dU + dPV<br />
<br />
Setelah itu, saya dijelaskan oleh pak Dai untuk setiap pelajaran yang akan dihadapi untuk selalu memulai dengan berdoa. Kami melakukan doa bersama sebelum melakukan pelajaran dan diajak oleh beliau untuk tidak pernah lupa kepada yang maha kuasa.<br />
<br />
'''Metode Numerik dan Phyton'''<br />
<br />
Pada mata kuliah metode numerik ini, kami menggunakan salah satu perangkat bernama ''Phyton''. Perangkat merupakan bahasa pemrograman untuk menyusun langkah-langkah dalam menyelesaikan suatu permasalahan melalui pemberian instruksi. Perangkat ini sedang marak digunakan oleh banyak orang sebagai bahasa pemrograman dan MIT sebagai salah satu perguruan tinggi yang tengah menggunakan perangkat lunak tersebut. Komputer sendiri tidak akan mengalami kelelahan apabila menghitung angka yang banyak. Kita harus membuat langkah-langkah menyelesaikan solusinya. Dikarenakan langkah-langkah yang panjang, diperlukan perubahan bahasa yang dimengerti oleh komputer. Bahasa yang biasanya kita mengerti akan diubah melalui interpreter menjadi bahasa mesin oleh komputer atau biasa disebut sebagai ''High Level Language''. Melalui perangkat ''Phyton'', model matematis sesulit apapun dengan ''High level language'', dapat dipecahkan dengan persamaan aljabar dari suatu numerik. Dalam suatu metode numerik, pasti terdapat persamaan-persamaan didalamnya. Misalkan persamaan berikut:<br />
<br />
A = B + C<br />
<br />
Pernyataan tersebut pada dasaranya tidak eksak sama sekali dan yang eksak hanyalah 'The One and Only', Tuhan. Persamaan tersebut memiliki bentuk yang lebih tepat sebagai berikut :<br />
<br />
R = A - (B + C)<br />
<br />
R merupakan residu dengan besaran yang mendekati 0<br />
<br />
Melalui programming tersebut, dapat diaktualisasikan pada kenyataan dengan metode numerik. Salah satu contohnya adalah prediksi badai yang akan datang sehingga masyarakat dapat melakukan evakuasi terlebih dahulu. Hal tersebut disebut dengan ''Weather Forecasting'' dan menggunakan model matematika yang sangat rumit disertai super komputer. Komputer hanya mengetahui operasi matematis tambah(+), bagi(:), kali(x), dan kurang(-). Komputer tidak mengetahui operasi integral dan hanya kita sendiri yang dapat memahaminya serta menyusunnya. Langkah-langkah instruksi tersebut disebut sebagai algoritma. Hal tersebut dapat dibantu dengan membentuk ''flowchart'' untuk mengetahui alur perhitungannya. <br />
<br />
'''Tugas 01'''<br />
<br />
[[Langkah pengerjaan Tugas 01]]<br />
----<br />
<br />
== Rabu, 11 September 2019 ==<br />
<br />
Pada hari ini, kami mendapatkan materi lebih dalam mengenai metode numerik. Metode numerik belajar mengenai penyelesaian model matematika dengan menggunakan ''High Level Language''. Permodelan komputer saat ini diperlukan oleh mahasiswa teknik mesin. Komputer memiliki sebuah database untuk menyimpan file. Contohnya adalah sebuah file game catur yang menyimpan langkah-langkah. Metode numerik saat ini juga digunakan untuk ''Artificial Intelligence''. Misalkan juga pada saat melakukan pencarian di internet, akan muncul pencarian dan hal-hal yang kita inginkan berdasarkan ''history'' yang sudah ada. <br />
<br />
Saat sedang mendownload suatu software, kita diberikan pilihan pilihan bit antara 32 dan 64 bit. 32 bit berarti intergernya berada pada tingkat 2^31, kemudian untuk 64 bit prosesnya akan lebih berbeda. Prosesor tersebut juga memiliki batas. Misalkan, pada 32 bit, berarti batas bawah dan atas yang direpresentasikan pada komputer hanya di dalam angka tersebut. Apabila kita menjalankan suatu proses yang lebih dari 32 bit, akan terjadi ''overflow''. Untuk mempresentasikannya diberikan bilangan biner, yaitu terdiri dari 0 dan 1. Huruf yang muncul pada komputer kita terdiri dari bilangan biner tersebut. Dalam memori, ada yang menampung data dalam bentuk angka biner. Jika dengan 64 bit, angka menghasilkan angka yang lebih besar sehingga lebih akurat dengan kualitas lebih baik. <br />
<br />
Komputer memiliki otak berupa memori. Manusia hanya memiliki memori terbatas. Akan tetapi, manusia memiliki hati. Menurut pak Dai, berpikir yang sesungguhnya adalah menggunakan hati. Otak kita hanyalah seperti komputer sebagai penyimpan memori atau database. Kita juga harus mengetahui keterbatasan kita. Apa yang dimiliki oleh komputer hanyalah ''Artificial Intelligence''. Yang ada pada manusia merupakan natural. Manusia sendirilah yang memiliki ''pure inteligence'' walaupun memiliki memori yang terbatas. <br />
<br />
Pada akhir pertemuan, kami diberikan latihan soal sebagai berikut : <br />
<br />
<br />
'''TUPLES'''<br />
<br />
rec=('Ales','Daniel',(10,27,1998))<br />
<br />
NamaAwal,NamaAkhir,TanggalLahir=rec #Unpacking the tuple<br />
<br />
print(NamaAkhir) #akan dicetak Daniel<br />
<br />
TahunLahir = TanggalLahir[2]<br />
<br />
print(TahunLahir) #akan dicetak 1998<br />
<br />
name = rec[0] + ' ' + rec[1]<br />
<br />
print(name) #akan dicetak Ales Daniel<br />
<br />
print(rec[0:2]) #akan dicetak ('Ales', 'Daniel')<br />
<br />
[[File:Capture Phyton Ales 2.JPG|1000px]]<br />
<br />
<br />
<br />
<br />
'''LISTS'''<br />
<br />
a = [1.0, 2.0, 3.0] #Create a list<br />
<br />
a.append(4.0) #Append 4.0 tp list<br />
<br />
print(a)<br />
<br />
a.insert(0, 0.0) #Insert 0.0 in position 0<br />
<br />
print(a)<br />
<br />
print(len(a)) #Determine length of list<br />
<br />
a[2:4] = [1.0, 1.0, 1.0] #Modify selected elements<br />
<br />
print(a)<br />
<br />
[[File:Capture_Phyton_Ales.JPG|1000px]]<br />
<br />
----<br />
<br />
== Rabu, 18 September 2019 ==<br />
<br />
[[Tugas Fungsi Fibonacci]]<br />
<br />
== TUGAS KELOMPOK GAUSS-ELIMINATION ==<br />
<br />
[[Hasil Pengerjaan Kelompok 2]]<br />
<br />
== Rabu, 9 Oktober 2019 ==<br />
<br />
Seorang ''engineer'' harus memiliki skill untuk memodelkan suatu hal. Kontinuum berarti semua hal mengisi segalanya. Misalkan sebuah meja yang memiliki massa mengisi isi mejanya. Kontinuum tersebut dapat dimodelkan secara matematis dalam persamaan diferensial.<br />
<br />
<br />
== Rabu, 16 Oktober 2019 ==<br />
<br />
KUIS<br />
<br />
<br />
1. Hasil Running Problem Set 2.1 No. 6<br />
<br />
<br />
<br />
<br />
2. Hasil Running Problem Set 7.1 No. 2<br />
<br />
x0 = 0<br />
y = 1<br />
h = 0.01<br />
x = 0.03<br />
<br />
<br />
#nilai x bisa berubah sesuai kebutuhan<br />
def dydx(x, y):<br />
return (x**2 - 4 * y)<br />
<br />
# Ini merupakan implementasi perhitungan Runge-Kutta.<br />
def rungeKutta(x0, y0, x, h):<br />
n = (int)((x - x0) / h)<br />
y = y0<br />
for i in range(1, n + 1):<br />
k1 = h * dydx(x0, y)<br />
k2 = h * dydx(x0 + 0.5 * h, y + 0.5 * k1)<br />
k3 = h * dydx(x0 + 0.5 * h, y + 0.5 * k2)<br />
k4 = h * dydx(x0 + h, y + k3)<br />
y = y + (1.0 / 6.0) * (k1 + 2 * k2 + 2 * k3 + k4)<br />
x0 = x0 + h<br />
return y<br />
<br />
<br />
print("Nilai dengan x =", x, "adalah", rungeKutta(x0, y, x, h))<br />
<br />
<br />
HASIL:<br />
Nilai dengan x = 0.03 adalah 0.9607897700333333<br />
<br />
<br />
== UJIAN TENGAH SEMESTER; RABU, 23 OKTOBER 2019 ==<br />
<br />
[[Pengerjaan 23 Oktober 2019]]<br />
<br />
[[Take Home Video]]<br />
<br />
Komentar dari teman di kanan dan kiri tempat duduk:<br />
<br />
<comments voting="Plus" /><br />
<br />
== Permodelan Persamaan Rudal Yang Meluncur ==<br />
<br />
Asumsi suatu rudal yang meluncur dengan gerakan miring dengan sudut tertentu. Rudal tersebut bergerak pada suatu posisi yang miring terhadap sumbu x dan y. Pada pengerjaan ini, rudal tersebut dianggap bergerak secara terus menerus pada kemiringan tertentu. Perhitungan yang akan dilakukan adalah turunannya terhadap sumbu x dan sumbu y. Berikut adalah permodelan matematis yang digunakan:<br />
<br />
dy/dt = (ay-(g+(cd*v**3/2)/m)<br />
<br />
dx/dt = (ax-(cd*v**3/2)/m)<br />
<br />
[[Algoritma Rudal X dan Y]]<br />
<br />
== Tugas Besar ==<br />
'''Spesifikasi Airfoil'''<br />
[[File:TB1.png]]<br />
Airfoil yang digunakan adalah MH 70 11.08% - Martin Hepperle MH70<br />
Span = 2 mm<br />
Root and Tip Chord = 10 mm <br />
<br />
'''Pembuatan model airfoil'''<br />
Airfoil dibuat dengan menggunakan software Autodesk Inventor<br />
[[File:TB2.png]]<br />
<br />
'''Simulasi menggunakan CFD'''<br />
Model yang sudah dibuat diimport ke CFDSOF<br />
[[File:TB3.png]]<br />
Model memasuki tahap ''meshing''<br />
<br />
Berikut adalah ''Boundary geometry'' untuk proses ''meshing''<br />
[[File:TB4.png]]<br />
<br />
Model memasuki tahap-tahap analisis sebagai berikut <br />
[[File:TB5.png]]<br />
<br />
[[File:TB6.png]]<br />
<br />
[[File:TB7.png]]<br />
<br />
[[File:TB8.png]]<br />
<br />
[[File:TB9.png]]<br />
<br />
[[File:TB10.png]]<br />
<br />
[[File:TB11.png]]<br />
<br />
[[File:TB12.png]]<br />
<br />
'''Perhitungan menggunakan Paraview'''<br />
Model ''meshing'' diimport ke Paraview<br />
Perhitungan dilakukan dengan tahap berikut<br />
[[File:TB12.png]]<br />
<br />
[[File:TB13.png]]<br />
<br />
[[File:TB14.png]]<br />
<br />
[[File:TB15.png]]<br />
<br />
[[File:TB16.png]]<br />
<br />
[[File:TB17.png]]<br />
<br />
[[File:TB18.png]]<br />
<br />
'''Hasil Percobaan'''<br />
''Data Percobaan''<br />
Data Percobaan<br />
[[File:TB19.png]]<br />
<br />
''Grafik Percobaan''<br />
Berikut adalah grafik lift dan drag kami<br />
[[File:TB20.png]]<br />
<br />
''Optimasi''<br />
Kode yang digunakan<br />
[[File:TB21.png]]<br />
<br />
Berikut hasil optimasi yang dilakukan<br />
[[File:TB22.png]]<br />
<br />
Grafik hasil optimasi Lift vs Drag<br />
<br />
[[File:TB23.png]]<br />
<br />
== Rabu, 27 November 2019 ==<br />
<br />
Pertemuan ini diadakannya kuis mengenai pengetahuan tentang metode numerik terutama tentang optimasi dan adanya pemahaman mengenai sebuah rumus. Setelah pertemuan tersebut, diadakannya presentasi mengenai tugas metode numerik, yaitu optimasi airfoil CFD per kelompok. Kami juga diminta untuk menuliskan seberapa banyaknya kontribusi terhadap kelompok tersebut. Optimasi yang dilakukan berdasarkan data yang didapatkan dengan variasi sudut yang sudah ditentukan. Software yang digunakan adalah CFDSOF untuk melakukan ''running'' airfoil yang digunakan. Hasil tersebut ditunjukkan pada pengerjaan tugas besar yang sudah tertera.<br />
<br />
== Rabu, 4 Desember 2019 ==<br />
<br />
Pertemuan ini merupakan lanjutan untuk presentasi mengenai optimasi airfoil yang sudah dikerjakan. Presentasi berdasarkan progress kelompok yang sudah dikerjakan selama ini. Kelas tersebut dilanjutkan dengan materi ANN atau Artificial Neural Networks. ANN sendiri merupakan sistem pembelajaran yang dibangun dari elemen sederhana berupan ''neuron''. ''Neuron'' ini mengambil keputusan sederhana dan saaling memberikan keputusan dengan yang lainnya.<br />
<br />
== Rabu, 11 Desember 2019 ==<br />
<br />
Pertemuan ini melanjutkan materi mengenai ANN dan diberikan tugas mengenai hal tersebut. Langkah dalam pembuatan ANN adalah sebagai berikut :<br />
<br />
1. Data Preprocessing<br />
<br />
2. Add input layer<br />
<br />
3. Random w init<br />
<br />
4. Add Hidden Layers<br />
<br />
5. Select Optimizer, Loss, and Performance Metrics<br />
<br />
6. Compile the model<br />
<br />
7. use model.fit to train the model<br />
<br />
8. Evaluate the model<br />
9. Adjust optimization parameters or model if needed</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=Ales_Daniel_-_1706036072&diff=55377Ales Daniel - 17060360722021-01-13T14:17:23Z<p>Alesdaniel: Undo revision 55376 by Alesdaniel (talk)</p>
<hr />
<div>[[File:alesdaniel.JPG|500px|thumb|center|Hello! Welcome to my page. My name is Ales and I'm pleased that you've visited my page. Enjoy!]]<br />
<br />
<br />
<br />
== ''Governing Equations'' Aliran Fluida ==<br />
<br />
Sebelum melakukan perhitungan pada aliran fluida dan perpindahan kalor, ada beberapa prinsip dasar yang perlu diperhatikan, yaitu konservasi massa (kontinuitas), momentum, dan energi. Pada dasarnya, berlaku hukum konservasi pada fisika dengan beberapa penjelasan sebagai berikut:<br />
1. Massa dari fluida dikonservasi<br />
2. Perubahan momentum sama dengan jumlah gaya yang terjadi pada partikel fluida (Hukum Kedua Newton)<br />
3. Perubahan energi sama dengan jumlah penambahan energi dan kerja yang diberikan pada partikel fluida (Hukum Pertama Termodinamika)<br />
<br />
Fluida tersebut akan dianggap sebagai sebuah ''continuum''. Pada saat melakukan analisa dari sistem tersebut, struktur dan gerakan molekuler dapat kita abaikan pada saat melakukan analisa. Fluida dapat kita asumsikan sebagai sebuah hal yang berukuran makroskopik seperti kecepatan, tekanan, massa jenis, temperatur, ruangnya, beserta perubahan waktunya. Semua fluida pada saat dilakukan perhitungan dianggap sebagai sebuah fungsi waktu dan ruang dengan beberapa sifat-sifat tertentu yang perlu ditinjau. Persamaan secara keseluruhan yang sudah dilakukan penurunan adalah sebagai berikut:<br />
<br />
[[File:GovEqAles.jpg|600px|thumb|center|''Governing Equations'' Aliran Fluida]]<br />
<br />
== Tugas Penurunan Rumus Kontinuitas dan Momentum ==<br />
<br />
[https://www.youtube.com/watch?v=VeYVEZfdr9E&list=PLLbF6f_08EZstokisa-DcZuPiqDqS6ZjZ&index=4&t=1s Video Penurunan Rumus dan Simulasi CFDSof]<br />
<br />
<br />
== Konveksi-Difusi dan Kuis Difusi ==<br />
<br />
[https://www.youtube.com/watch?v=YjAouwbj98Y&list=PLLbF6f_08EZu7yDcpOk69V07OwrlijX61&index=2&t=440s Video FVM for Diffusion]<br />
<br />
== SIMPLE Method ==<br />
<br />
Pada kelas terakhir (22 Oktober 2020) dijelaskan bahwa dengan metode staggered grid, kita dapat melakukan pembagian perhitungan berdasarkan control volume tertentu dan dibagi berdasarkan variabel skalar atau vektor. Salah satu metode yang digunakan adalah SIMPLE. Metode ini melakukan guessing atau menebak sebuah variabel tertentu yang ingin dicari pada sebuah permasalahan. Variabel tersebut kemudian dilakukan diskritisasi momentum dan persamaan pressure. Setelah dilakukan perhitungan, dapat dilakukan correction dengan menghitung deviasi yang terjadi pada perhitungan tersebut. Tentunya, diperlukan juga kondisi under-relaxation factor, untuk mengurangi kemungkinan perhitungan iterasi menjadi divergence. Angka tersebut apabila menggunakan besaran yang tepat, dapat menghasilkan simulasi yang cukup efektif dengan hasil convergence. Kalau terlalu besar, akan menghasilkan ketidakseimbangan perhitungan yang berujung pada divergence pada iterasi yang dilakukan.<br />
<br />
[[File:SIMPLEAles.jpg|400px|thumb|center|Algoritma dari SIMPLE]]<br />
<br />
== 6Dof and Dynamic Mesh ==<br />
<br />
''Six degrees of freedom'' merupakan sebuah gerakan dari objek yang bisa bergerak secara tiga dimensi, terukur dari titik ''center of gravity''-nya atau CoG. Pada simulasi menggunakan CFD, sebuah fluida yang mengalir akan bergerak secara translasi dan rotasi. Translasi terukur berdasarkan perubahan kecepatan terhadap perubahan waktu, atau secara rumus merupakan '''SygmaF = massa x akselerasi''', dimana total gaya yang dihasilkan berdasarkan perubahan massa sebuah objek terhadap perpindahan benda yang berubah terhadap waktu. Sedangkan kalau berdasarkan rotasi, terukur dengan istilah ''angular velocity'' berdasarkan torsi terhadap momen inersia dari objek yang terukur. Rumus yang digunakan adalah '''SygmaMoment = Moment Inertia x Akselerasi angular'''.<br />
<br />
Berdasarkan ini, simulasi yang dilakukan pada CFD Solver akan digunakan untuk ''Dynamic Mesh''. Pada kasus fluida yang mengalir dalam sistem apapun, CFD akan melakukan perhitungan berdasarkan posisi yang berubah baik secara translasi maupun rotasi secara metode komputasi. Mesh tersebut akan berubah-ubah sesuai dengan gaya yang bekerja pada sistem tertentu. Pada topik ini, diberikan contoh simulasi berupa ''Vertical-Axis Wind Turbine'', yang ditunjukkan dari tampak atas untuk mengetahui fenomena yang terjadi. Simulasi dilakukan dua kali dengan dua kondisi yang dimodifikasi berbeda. Kondisi yang diubah ditunjukkan berdasarkan data sebagai berikut:<br />
<br />
1.<br />
<br />
Control Dict<br />
<br />
- Max Delta T : 0.01<br />
<br />
- End Time 10<br />
<br />
<br />
Dynamic Mesh Dict<br />
<br />
- //g (0 9.8 0);<br />
<br />
// :: lOD :: angularMomentum (default = (0 10 0))<br />
<br />
<br />
2.<br />
<br />
Control Dict<br />
<br />
- Max Delta T : 0.01<br />
<br />
- End Time 10<br />
<br />
Dynamic Mesh Dict<br />
<br />
- //g (0 9.8 0);<br />
<br />
// :: lOD :: angularMomentum (default = (0 100 0))<br />
<br />
//- Angular momentum of the rigid-body in local reference frame<br />
<br />
angularMomentum (10 10 10);<br />
<br />
<br />
Hasil yang didapatkan adalah berdasarkan gambar sebagai berikut:<br />
<br />
1. Hasil simulasi 1<br />
<br />
[[File:VAWT Ales1.jpg|500px|center]]<br />
<br />
<br />
<br />
2. Hasil simulasi 2<br />
<br />
[[File:VAWT Ales2.jpg|500px|center]]<br />
<br />
<br />
== Economizer Hopper (CFDSof Simulation) ==<br />
<br />
Economizer Hopper merupakan alat untuk mengatasi permasalahan akibat ''fly ash'' yang berasal dari produk pembakaran batubara. Potensi yang mungkin terjadi adalah penumpukan ''fly ash'' pada economizer ''flue gas ducting'', ''blocking'' abu di elemen pre-air heater, serta pengikisan pada blade dan ''guide vane''. Dengan adanya modifikasi Hopper tersebut, abu atau ''fly ash'' yang dialirkan saat keluar dari Boiler akan tertampung pada bagian ''bottom ash'' tersebut. <br />
<br />
Pada kasus ini, dilakukan simulasi menggunakan CFDSof dengan melakukan pembeda antara economizer dengan hopper dan tidak. Analisa yang dilakukan adalah dengan simulasi secara ''transient'', kemudian dilakukan simulasi multifasa dengan pendekatan ''eulerian-langrangian'', dengan fasa padatan dalam bentuk ''fly ash'' serta liquid dalam bentuk gas yang mengalir pada sistem tersebut. <br />
<br />
Hasil dari simulasi tersebut digambarkan melalui dokumentasi yang sudah dibagi berdasarkan beberapa tinjauan sebagai berikut:<br />
<br />
<br />
<br />
'''Analisa diameter partikel'''<br />
<br />
1. Tanpa Hopper<br />
<br />
<br />
[[File:EconomizerTanpaHopper.gif|center|400px]]<br />
<br />
[[File:Ales_ETH_Iso.gif|center|400px]]<br />
<br />
<br />
<br />
2. Dengan Hopper<br />
<br />
[[File:Ales_EH.gif|center|400px]]<br />
<br />
[[File:Ales_EH_Iso.gif|center|400px]]<br />
<br />
<br />
Melalui hasil ini, dapat disimpulkan bahwa dengan penggunaan hopper, mampu menangkap partikel ''fly ash'' pada wadah tertentu. Simulasi yang dilakukan dapat terlihat dari partikel berwarna merah yang mampu ditampung pada wadah tertentu saat melalui jalur tersebut. Partikel dengan ukuran yang lebih kecil, cenderung dapat melanjutkan sampai ke bagian outlet dari economizer hopper tersebut.<br />
<br />
<br />
----<br />
<br />
'''Analisa tekanan sistem'''<br />
<br />
<br />
[[File:Pressure_Econo_Ales.gif|center|400px]]<br />
<br />
<br />
Pada hasil dari kedua simulasi tersebut, dapat terlihat bahwa tekanan pada bagian ''outflow'' semakin besar daripada bagian inlet dari sistem untuk kedua hasil uji coba. Hasil ini dikarenakan adanya perbedaan ketinggian yang terjadi sembari berjalannya ''fly ash'' kepada arah outflow tersebut. Tekanan ini diakibatkan karena adanya kecepatan di bagian inlet yang juga bisa mempengaruhi tekanan pada outlet tersebut. Tekanan ini terjadi pada sistem tersebut dan dapat mempengaruhi partikel yang bergerak melalui sistem tersebut. Pengaruh yang terjadi adalah kecepatan sistem tersebut untuk bergerak sepanjang sistem yang akan cenderung lebih cepat seiring dalam semakin besarnya tekanan pada sistem.<br />
<br />
----<br />
<br />
'''Analisa kecepatan sistem'''<br />
<br />
[[File:Velocity_Econo_Ales.gif|center|400px]]<br />
<br />
Partikel tersebut akan bergerak terus menerus dan ada yang diakibatkan oleh kesetimbangan gaya (''bouyancy''), sehingga beberapa partikel bergerak dengan kecepatan yang berbeda. Partikel dengan massa yang lebih besar akan cenderung lebih dahulu, sedangkan yang tidak akan lebih mengalami gaya apung di dalam sistem tersebut. Dapat terlihat bahwa partikel dengan massa yang lebih berat (berdasarkan diameter) lebih dahulu menyentuh hopper (pada bagian dengan ada hopper) dan terjebak di dalam hopper tersebut. Sedangkan untuk yang lebih ringan, dengan kecepatan yang lebih pelan, akan cenderung mengapung dan masih ada kemungkinan bergerak ke bagian outlet dari sistem tersebut.<br />
<br />
== Validasi dan Verifikasi ==<br />
<br />
Validasi dan verifikasi menjadi salah satu langkah untuk melakukan simulasi CFD dengan secara kuantitatif mengestimasi error yang tetap serta ketidakpastian dalam simulasi numerikal. Walaupun keduanya memiliki definisi yang cukup dekat, kedua ini berdasarkan AIAA Guide (1998) menjadi dua hal yang sangat berbeda. <br />
<br />
'''Validasi''' : ''Solve the right equation'', berarti sebuah proses untuk memasukkan model simulasi yang tidak pasti dengan melakukan ''benchmarking'' dari data eksperimental. Apabila kondisi memenuhi, maka besaran dan tanda akan menyesuaikan error secara sendirinya dalam melakukan simulasi. Dalam prosedur ini dasarnya adalah melakukan pemastian hitungan dengan memberikan beberapa jangkauan kondisi fisik dari sistem yang didapatkan berasarkan perhitungan dan dibandingkan dengan hasil simulasi numerikal dalam beragam kondisi. Dari perbandingan terhadap kondsisi eksperimental ini, dapat terlihat seberapa jauh kesalahan yang terjadi.<br />
<br />
'''Verifikasi''' : ''Solve the equation right'', berarti sebuah proses untuk memasukkan simulasi numerikal yang tidak pasti dan apabila sesuai, memastikan besaran dan tanda dari error simulasi tersebut serta ketidakpastiannya. Pada bagian ini dasarnya adalah memastikan parameter yang digunakan pada saat dilakukan simulasi. Hal ini juga perlu diperhatikan besar mesh yang digunakan serta time-step yang terjadi, apakah sesuai atau tidak dalam dilakukan perhitungan tersebut.<br />
<br />
== Analisis CFD dalam Simulasi Cyclone Seperator ==<br />
<br />
'''Validasi'''<br />
<br />
[[File:GeomPaperAles.jpg|400px|center]]<br />
<br />
Pada kasus ini, dilakukan benchmarking berdasarkan paper ''Numerical Analysis of Gas-Solid Behavior in a Cyclone Separator for Circulating Fluidized Bed System'' (DOI:10.18869/acadpub.jafm.73.241.26951). Paper ini memberikan contoh ''property'' dari partikel solid berupa pasir dengan jangkauan diameter per partikel sekitar 100-425 µm dan kecepatan aliran pada bagian inlet sekitar 16 m/s. Alat ini pada dasarnya bekerja dengan memasukkan gas-solid pada bagian inlet dari sistem tersebut secara tangensial. Percepatan kemudian terbentuk secara ''helical'' karena bentuk dinding yang berupa ''cone''. Partikel yang lebih berat akan cenderung jatuh ke bawah, yaitu bagian outlet tersebut. Sedangkan, partikel yang lebih kecil lagi (seperti udara) akan mengalir mengarah bagian tengah dan mengarah ke ''vortex finder'' dari sistem tersebut. Hal ini akan membuat udara tersebut keluar pada bagian outlet di atas sistem.<br />
<br />
<br />
[[File:RSMTransportEqAles.jpg|400px|center]]<br />
<br />
Persamaan yang digunakan ini adalah ''transport equation'' untuk Reynolds stress model. Ruas kiri menunjukkan derivasi stress terhadap waktu dan ''convective transport'' pada sistem tersebut. Kemudian, ruas kanan menunjukkan beberapa variabel seperti ''stress diffusion'', ''shear production'', ''pressure-strain'', ''dissipation term'', dan Source ''S'' yang terjadi pada sistem tersebut. Berdasarkan paper ini, interaksi antar particle juga diabaikan untuk dilakukan analisa komputasi yang dilakukan. <br />
<br />
<br />
----<br />
'''Verifikasi'''<br />
<br />
Pada simulasi yang dilakukan, dilakukan dengan kondisi multiphase eulerian-langrangian untuk dilakukan simulasi ini. Kondisi tersebut kemudian dilanjutkan dengan distribusi partikel uniform dengan sekitar 4000 parcel per detiknya selama dua detik. Mesh pada geometri ini pada Δx, Δy, dan Δz, adalah masing-masing 18, 50, dan 21. Distribusi partikel (pasir) diasumsikan ''uniform'' (dengan alasan belum memahami perbedaannya), dengan range diameter seperti yang sudah dijelaskan pada bagian validasi serta kecepatan inlet (pada sumbu z pada geometri ini) dengan sebesar 16 m/s, sesuai dengan kecepatan inlet udara. Pada bagian geometri, inlet diasumsikan udara dengan 1.225 kg/m^3 dengan kecepatan 16 m/s. Bagian outlet atas dan bawah diasumsikan sebagai outflow sehingga udara dapat mengalir pada bagian tersebut. Simulasi yang dilakukan belum banyak dilakukan variasi karena sering terjadi ''error'' pada saat dilakukan simulasi. Setelah dilakukan diagnosa, kesalahan yang terjadi adalah adanya ''adjust time step'' yang dicentang sehingga mengalami ''error'' dan cenderung untuk mengalami software crash pada saat dilakukan. Berikut adalah bukti ''error'' yang terjadi pada saat dilakukan simulasi:<br />
<br />
<br />
[[File:CrashAles.jpg|400px|center]]<br />
<br />
[[File:ConvergeFailAles.jpg|300px|center]]<br />
<br />
<br />
<br />
Hasil ini menunjukkan bahwa sudah dilakukan percobaan dengan kondisi ''adjust time step'' sebagai berikut dengan iterasi tertentu. Kondisi ini menyebabkan adanya crash pada sistem tersebut sehingga tidak bisa dilakukan simulasi dengan kondisi ''adjust time step''. Akan tetapi, dilakukan simulasi kembali dengan kondisi ''boundary conditions'' yang sama namun dengan kondisi ''adjust time step'' yang tidak dilakukan variasi. Hal ini berhasil melakukan simulasi dengan baik, akan tetapi terjadi beberapa permasalahan yang terjadi juga pada kondisi ini.<br />
<br />
<br />
----<br />
<br />
'''Diameter Partikel'''<br />
<br />
[[File:CycDWTSAles.jpg|400px|left]]<br />
[[File:ParticleTraceAles.jpg|400px|right]]<br />
<br />
[[File:AlesResidual16.jpg|400px|thumb|center|Residual Perhitungan yang Masih Salah]]<br />
<br />
Gambar berikut menunjukkan hasil yang sudah ditunjukkan tanpa dengan melakukan ''adjust time step''. Terlihat walaupun cukup kecil bahwa adanya partikel (pasir) yang terjatuh ke bagian outflow bawah. Gas atau udara yang bersih seharusnya keluar pada bagian outflow atas, akan tetapi tidak dapat divisualisasikan melalui hasil simulasi yang sudah dilakukan. Time step yang tidak dilakukan penyesuaian pada simulasi tersebut menyebabkan adanya residual untuk ''turbulence'' menjadi sangat besar, sehingga masih banyak sekali kesalahan yang terjadi pada simulasi ini. Tinjauan ini setidaknya masih menunjukkan bahwa partikel tersebut dapat terpisahkan melalui bagian outflow di bawah, walaupun visualisasinya kurang begitu jelas dikarenakan diameter partikel yang relatif sangat kecil. <br />
<br />
<br />
'''Tekanan Sistem'''<br />
<br />
[[File:PressGraphY.jpg|400px|center]]<br />
<br />
[[File:CycPressWTSAles.jpg|400px|center]]<br />
<br />
<br />
Tekanan yang terjadi ini terlihat melalui visualisasi bahwa kecepatan inlet tersebut menyebabkan adanya tekanan yang besar pada bagian satu sisi dari dinding ''cyclone separator''. Hal ini karena kecepatan yang mendorong dinding tersebut ditambah lagi adanya partikel pasir yang terlibat pada fenomena tersebut. Berdasarkan grafik yang didapatkan juga, terlihat bahwa tekanan cenderung lebih besar pada bagian sisi atas dari sistem tersebut, daripada yang bagian bawah. Seharusnya ada variasi perbedaan terkanan yang terjadi akibat adanya inlet ini, namun dikarenakan simulasi yang begitu terbatas, tidak dapat terlihat secara jelas mengenai grafik tersebut. Bagian outflow atas dan bawah juga tervisualisasi bahwa adanya tekanan yang meningkat akibat adanya aliran tersebut. Perlu adanya beberapa koreksi seperti distribusi partikel yang terjadi pada sistem dan juga mesh yang perlu diperbaiki pada saat dilakukan simulasi.<br />
<br />
<br />
<br />
'''Evaluasi Pekerjaan'''<br />
<br />
Grafik lainnya tidak menunjukkan hasil yang jelas setelah dilakukan simulasi. Grafik partikel, kecepatan, turbulent, dan lain-lainnya tidak dapat divisualisasikan dengan jelas karena keterbatasan simulasi yang dilakukan. Perlu adanya perhatian yang lebih dalam terkait distribusi partikel tersebut serta visualisasi dari aliran udara, sehingga bisa ditunjukkan terpisahnya jalur udara bersih dan partikel pasir yang ada. Akan tetapi, grafik dan visualisasi yang ditunjukkan tersebut cukup menunjukkan mengenai fenomena multifasa yang terjadi pada sistem ''cyclone separator''. Oleh karena itu, dilakukan perbaikan terkait kesalahan yang terjadi tersebut menjadi lebih baik.<br />
<br />
<br />
'''Hasil Evaluasi'''<br />
<br />
Pada simulasi ini, dilakukan pembeda yaitu pada kecepatan inlet dijadikan 5 m/s. Alasan ini masih belum diketahui penyebabnya, namun didapatkan bahwa grafik residunya sudah ''converge'' dan bisa dilakukan pada waktu sekitar 8 detik (sesuai dengan paper). Kondisi pada parcelnya dibedakan menjadi 2000 per second dengan lama waktu selama dua detik. Hal ini ditemukan adanya grafik kecepatan serta visualisasi pada sistem tersebut yang sudah benar. Tekanan sudah terdistribusi dengan baik serta terdapat visualisasi kecepatan yang keluar pada kedua outlet yang menunjukkan adanya udara mengarah ke atas. Grafik juga tersedia sebagai bukti adanya tekanan dan kecepatan yang menunjukkan hasil tersebut. Hasil yang didapatkan adalah sebagai berikut:<br />
<br />
[[File:Residual1Ales.jpg|400px|thumb|center|Hasil Residual pada percobaan dengan v=5 m/s]]<br />
<br />
Pada hasil yang didapatkan, terlihat bahwa partikel yang digambarkan melalui vektor dengan warna bergerak dengan kecepatan yang bervariasi berdasarkan beratnya. Terlihat bahwa partikel tersebut berputar mengitari dinding cyclone dan mengarah ke bawah dalam beberapa detik. Dikarenakan hanya ditetapkan sekitar dua detik untuk masuk sebanyak 2000 parcels per second, maka setelah dua detik, tidak ada lagi partikel yang memasuki sistem tersebut. Setelah itu, terlihat bahwa gerakan partikel mengarah ke outlet di bagian bawah dan seketika tidak terlihat pada visualisasi tersebut. Dapat ditunjukkan bahwa adanya kecepatan inlet tersebut mendorong partikel untuk bergerak secara tangensial dan secara ''helical'' ke bagian outlet. Penggambaran terlihat sebagai berikut:<br />
<br />
[[File:DvectorAles.gif|450px|thumb|center|Vektor Arah Partikel Berdasarkan Ukuran Diameter]]<br />
[[File:VelocityVAles.gif|450px|thumb|center|Vektor Kecepatan Partikel]]<br />
<br />
Distribusi tekanan dan kecepatan terlihat setelah adanya inlet yang masuk dengan besaran tertentu. Pertama melalui tekanan, terlihat bahwa adanya distribusi tekanan yang relatif besar pada bagian atas wall. Ini dikarenakan adanya tekanan dari inlet yang membuat tekanan terpusat di awal dinding tersebut. Kemudian, tekanan tersebut mulai tersebar dengan warna yang mulai berubah sepanjang wall dari ''cyclone'' tersebut. Disini terlihat bahwa persebaran tekanan sebenarnya bergerak juga secara helikal, namun tidak merata sama besarnya karena adanya kecepatan yang cenderung berubah relatif lebih lambat. Kemudian, distribusi kecepatan terlihat bahwa adanya partikel yang awal mulanya mengenai dinding dari inlet tersebut, kemudian tervisualisasi secara gradasi bahwa kecepatan mulai melambat setelah melewati inlet tersebut. Partikel yang jatuh ke bawah terlihat bahwa outlet tersebut menunjukkan adanya partikel yang terjatuh pada bagian itu. Dinding juga ada yang berubah warna menjadi lebih hijau (menandakan kenaikan kecepatan) serta adanya kenaikan kecepatan pada outlet bagian atas. Ini juga menunjukkan bahwa adanya udara yang juga mengarah keatas akibat vortex finder dari sistem. Visualisasi dari simulasi tersebut terlihat di bawah berikut:<br />
<br />
[[File:PressureDisAles.gif|400px|thumb|center|Distribusi Tekanan]]<br />
[[File:VelocityDisAles.gif|400px|thumb|center|Distribusi Kecepatan]]<br />
<br />
<br />
Lalu dari hasil grafik, dapat terlihat juga bahwa pada sumbu Z (horizontal pada dinding), tekanan pada bagian tengah cenderung mengecil dan besar pada bagian dekat dinding. Dapat terlihat bahwa tekanan tersebut besar karena adanya partikel yang berputar mengarah ke dinding tersebut. Pada sumbu Y (vertikal terhadap dinding), cenderung membesar pada bagian bawah dan atas juga cukup besar, akan tetapi mengecil juga pada sepanjang titik tengah dari dinding ''cyclone'' tersebut. Kecepatan pada sumbu Z juga terlihat cukup besar (secara magnitude). Dapat ditunjukkan juga bahwa bagian tengah tersebut relatif besar (pada sumbu Z) karena tidak adanya gesekan terhadap dinding sehingga relatif untuk mengalami gerak jatuh bebas. Berbeda dengan yang di dekat dinding, adanya gesekan membuat kecepatan menjadi relatif kecil. Secara sumbu Y, terlihat bahwa adanya kecepatan dengan besaran yang selalu ada. Besarannya berbeda-beda, pengaruh juga dari tekanan yang juga berbeda-beda. Besaran ini mungkin belum tentu akurat (karena adanya faktor error atau mesh), akan tetapi sudah cukup menunjukkan adanya fenomena yang kurang lebih benar terjadi pada sistem ''cyclone separator'' tersebut. Berikut adalah grafik mengenai hasil pada sumbu Z dan Y:<br />
<br />
<br />
[[File:GraphZ1.jpg|300px|thumb|center|Grafik pada Sumbu Y (Inlet 5 m/s)]]<br />
[[File:GraphY1Ales.jpg|300px|thumb|center|Grafik pada Sumbu Y (Inlet 5 m/s)]]<br />
<br />
== Sinopsis Tugas Besar Aplikasi CFD ==<br />
<br />
<br />
'''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''<br />
<br />
The gas-liquid separator has been widely used in the oil and gas industry to improve product quality. To design and operate the system at a low cost, mathematical modeling becomes very useful. The separator apparatus has three geometrical designs, such as horizontal, vertical, and spherical types, with the horizontal design with the lowest expense in production processes. The horizontal design has three main processes: the separation process, the liquid outlet process, and the gas outlet process. First, the separation process involves a diverter that reduces the gas-liquid velocity and diverts downwards into the separator affected by gravity. Then, the liquid droplets that are larger than a certain size will fall into the separator and continue their flow with a certain amount of liquid at the bottom of the separator to the system's outlet. Finally, the rest of the droplets with a smaller amount of size are considered a gas, which will continue its flow into the upper outlet. The study will use Computational Fluid Dynamics with Multiphase Eulerian-Langrangian method. There will be a variation between a diverter and the flow inlet distance, measured upon its efficiency in separating the gas and the fluid.<br />
<br />
== [[TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator''']] ==<br />
<br />
== Referensi Pembelajaran ==<br />
<br />
<br />
[1] Versteeg, H.K. and Malalasekera, W., 2007. An introduction to computational fluid dynamics: the finite volume method. Pearson education.<br />
<br />
[2] Tu, J., Yeoh, G.H. and Liu, C., 2018. Computational fluid dynamics: a practical approach. Butterworth-Heinemann.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=Ales_Daniel_-_1706036072&diff=55376Ales Daniel - 17060360722021-01-13T14:16:26Z<p>Alesdaniel: /* TUGAS BESAR APLIKASI CFD: Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator */</p>
<hr />
<div>[[File:alesdaniel.JPG|500px|thumb|center|Hello! Welcome to my page. My name is Ales and I'm pleased that you've visited my page. Enjoy!]]<br />
<br />
<br />
<br />
== ''Governing Equations'' Aliran Fluida ==<br />
<br />
Sebelum melakukan perhitungan pada aliran fluida dan perpindahan kalor, ada beberapa prinsip dasar yang perlu diperhatikan, yaitu konservasi massa (kontinuitas), momentum, dan energi. Pada dasarnya, berlaku hukum konservasi pada fisika dengan beberapa penjelasan sebagai berikut:<br />
1. Massa dari fluida dikonservasi<br />
2. Perubahan momentum sama dengan jumlah gaya yang terjadi pada partikel fluida (Hukum Kedua Newton)<br />
3. Perubahan energi sama dengan jumlah penambahan energi dan kerja yang diberikan pada partikel fluida (Hukum Pertama Termodinamika)<br />
<br />
Fluida tersebut akan dianggap sebagai sebuah ''continuum''. Pada saat melakukan analisa dari sistem tersebut, struktur dan gerakan molekuler dapat kita abaikan pada saat melakukan analisa. Fluida dapat kita asumsikan sebagai sebuah hal yang berukuran makroskopik seperti kecepatan, tekanan, massa jenis, temperatur, ruangnya, beserta perubahan waktunya. Semua fluida pada saat dilakukan perhitungan dianggap sebagai sebuah fungsi waktu dan ruang dengan beberapa sifat-sifat tertentu yang perlu ditinjau. Persamaan secara keseluruhan yang sudah dilakukan penurunan adalah sebagai berikut:<br />
<br />
[[File:GovEqAles.jpg|600px|thumb|center|''Governing Equations'' Aliran Fluida]]<br />
<br />
== Tugas Penurunan Rumus Kontinuitas dan Momentum ==<br />
<br />
[https://www.youtube.com/watch?v=VeYVEZfdr9E&list=PLLbF6f_08EZstokisa-DcZuPiqDqS6ZjZ&index=4&t=1s Video Penurunan Rumus dan Simulasi CFDSof]<br />
<br />
<br />
== Konveksi-Difusi dan Kuis Difusi ==<br />
<br />
[https://www.youtube.com/watch?v=YjAouwbj98Y&list=PLLbF6f_08EZu7yDcpOk69V07OwrlijX61&index=2&t=440s Video FVM for Diffusion]<br />
<br />
== SIMPLE Method ==<br />
<br />
Pada kelas terakhir (22 Oktober 2020) dijelaskan bahwa dengan metode staggered grid, kita dapat melakukan pembagian perhitungan berdasarkan control volume tertentu dan dibagi berdasarkan variabel skalar atau vektor. Salah satu metode yang digunakan adalah SIMPLE. Metode ini melakukan guessing atau menebak sebuah variabel tertentu yang ingin dicari pada sebuah permasalahan. Variabel tersebut kemudian dilakukan diskritisasi momentum dan persamaan pressure. Setelah dilakukan perhitungan, dapat dilakukan correction dengan menghitung deviasi yang terjadi pada perhitungan tersebut. Tentunya, diperlukan juga kondisi under-relaxation factor, untuk mengurangi kemungkinan perhitungan iterasi menjadi divergence. Angka tersebut apabila menggunakan besaran yang tepat, dapat menghasilkan simulasi yang cukup efektif dengan hasil convergence. Kalau terlalu besar, akan menghasilkan ketidakseimbangan perhitungan yang berujung pada divergence pada iterasi yang dilakukan.<br />
<br />
[[File:SIMPLEAles.jpg|400px|thumb|center|Algoritma dari SIMPLE]]<br />
<br />
== 6Dof and Dynamic Mesh ==<br />
<br />
''Six degrees of freedom'' merupakan sebuah gerakan dari objek yang bisa bergerak secara tiga dimensi, terukur dari titik ''center of gravity''-nya atau CoG. Pada simulasi menggunakan CFD, sebuah fluida yang mengalir akan bergerak secara translasi dan rotasi. Translasi terukur berdasarkan perubahan kecepatan terhadap perubahan waktu, atau secara rumus merupakan '''SygmaF = massa x akselerasi''', dimana total gaya yang dihasilkan berdasarkan perubahan massa sebuah objek terhadap perpindahan benda yang berubah terhadap waktu. Sedangkan kalau berdasarkan rotasi, terukur dengan istilah ''angular velocity'' berdasarkan torsi terhadap momen inersia dari objek yang terukur. Rumus yang digunakan adalah '''SygmaMoment = Moment Inertia x Akselerasi angular'''.<br />
<br />
Berdasarkan ini, simulasi yang dilakukan pada CFD Solver akan digunakan untuk ''Dynamic Mesh''. Pada kasus fluida yang mengalir dalam sistem apapun, CFD akan melakukan perhitungan berdasarkan posisi yang berubah baik secara translasi maupun rotasi secara metode komputasi. Mesh tersebut akan berubah-ubah sesuai dengan gaya yang bekerja pada sistem tertentu. Pada topik ini, diberikan contoh simulasi berupa ''Vertical-Axis Wind Turbine'', yang ditunjukkan dari tampak atas untuk mengetahui fenomena yang terjadi. Simulasi dilakukan dua kali dengan dua kondisi yang dimodifikasi berbeda. Kondisi yang diubah ditunjukkan berdasarkan data sebagai berikut:<br />
<br />
1.<br />
<br />
Control Dict<br />
<br />
- Max Delta T : 0.01<br />
<br />
- End Time 10<br />
<br />
<br />
Dynamic Mesh Dict<br />
<br />
- //g (0 9.8 0);<br />
<br />
// :: lOD :: angularMomentum (default = (0 10 0))<br />
<br />
<br />
2.<br />
<br />
Control Dict<br />
<br />
- Max Delta T : 0.01<br />
<br />
- End Time 10<br />
<br />
Dynamic Mesh Dict<br />
<br />
- //g (0 9.8 0);<br />
<br />
// :: lOD :: angularMomentum (default = (0 100 0))<br />
<br />
//- Angular momentum of the rigid-body in local reference frame<br />
<br />
angularMomentum (10 10 10);<br />
<br />
<br />
Hasil yang didapatkan adalah berdasarkan gambar sebagai berikut:<br />
<br />
1. Hasil simulasi 1<br />
<br />
[[File:VAWT Ales1.jpg|500px|center]]<br />
<br />
<br />
<br />
2. Hasil simulasi 2<br />
<br />
[[File:VAWT Ales2.jpg|500px|center]]<br />
<br />
<br />
== Economizer Hopper (CFDSof Simulation) ==<br />
<br />
Economizer Hopper merupakan alat untuk mengatasi permasalahan akibat ''fly ash'' yang berasal dari produk pembakaran batubara. Potensi yang mungkin terjadi adalah penumpukan ''fly ash'' pada economizer ''flue gas ducting'', ''blocking'' abu di elemen pre-air heater, serta pengikisan pada blade dan ''guide vane''. Dengan adanya modifikasi Hopper tersebut, abu atau ''fly ash'' yang dialirkan saat keluar dari Boiler akan tertampung pada bagian ''bottom ash'' tersebut. <br />
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Pada kasus ini, dilakukan simulasi menggunakan CFDSof dengan melakukan pembeda antara economizer dengan hopper dan tidak. Analisa yang dilakukan adalah dengan simulasi secara ''transient'', kemudian dilakukan simulasi multifasa dengan pendekatan ''eulerian-langrangian'', dengan fasa padatan dalam bentuk ''fly ash'' serta liquid dalam bentuk gas yang mengalir pada sistem tersebut. <br />
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Hasil dari simulasi tersebut digambarkan melalui dokumentasi yang sudah dibagi berdasarkan beberapa tinjauan sebagai berikut:<br />
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'''Analisa diameter partikel'''<br />
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1. Tanpa Hopper<br />
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[[File:EconomizerTanpaHopper.gif|center|400px]]<br />
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[[File:Ales_ETH_Iso.gif|center|400px]]<br />
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2. Dengan Hopper<br />
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[[File:Ales_EH.gif|center|400px]]<br />
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[[File:Ales_EH_Iso.gif|center|400px]]<br />
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Melalui hasil ini, dapat disimpulkan bahwa dengan penggunaan hopper, mampu menangkap partikel ''fly ash'' pada wadah tertentu. Simulasi yang dilakukan dapat terlihat dari partikel berwarna merah yang mampu ditampung pada wadah tertentu saat melalui jalur tersebut. Partikel dengan ukuran yang lebih kecil, cenderung dapat melanjutkan sampai ke bagian outlet dari economizer hopper tersebut.<br />
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'''Analisa tekanan sistem'''<br />
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[[File:Pressure_Econo_Ales.gif|center|400px]]<br />
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Pada hasil dari kedua simulasi tersebut, dapat terlihat bahwa tekanan pada bagian ''outflow'' semakin besar daripada bagian inlet dari sistem untuk kedua hasil uji coba. Hasil ini dikarenakan adanya perbedaan ketinggian yang terjadi sembari berjalannya ''fly ash'' kepada arah outflow tersebut. Tekanan ini diakibatkan karena adanya kecepatan di bagian inlet yang juga bisa mempengaruhi tekanan pada outlet tersebut. Tekanan ini terjadi pada sistem tersebut dan dapat mempengaruhi partikel yang bergerak melalui sistem tersebut. Pengaruh yang terjadi adalah kecepatan sistem tersebut untuk bergerak sepanjang sistem yang akan cenderung lebih cepat seiring dalam semakin besarnya tekanan pada sistem.<br />
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'''Analisa kecepatan sistem'''<br />
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[[File:Velocity_Econo_Ales.gif|center|400px]]<br />
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Partikel tersebut akan bergerak terus menerus dan ada yang diakibatkan oleh kesetimbangan gaya (''bouyancy''), sehingga beberapa partikel bergerak dengan kecepatan yang berbeda. Partikel dengan massa yang lebih besar akan cenderung lebih dahulu, sedangkan yang tidak akan lebih mengalami gaya apung di dalam sistem tersebut. Dapat terlihat bahwa partikel dengan massa yang lebih berat (berdasarkan diameter) lebih dahulu menyentuh hopper (pada bagian dengan ada hopper) dan terjebak di dalam hopper tersebut. Sedangkan untuk yang lebih ringan, dengan kecepatan yang lebih pelan, akan cenderung mengapung dan masih ada kemungkinan bergerak ke bagian outlet dari sistem tersebut.<br />
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== Validasi dan Verifikasi ==<br />
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Validasi dan verifikasi menjadi salah satu langkah untuk melakukan simulasi CFD dengan secara kuantitatif mengestimasi error yang tetap serta ketidakpastian dalam simulasi numerikal. Walaupun keduanya memiliki definisi yang cukup dekat, kedua ini berdasarkan AIAA Guide (1998) menjadi dua hal yang sangat berbeda. <br />
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'''Validasi''' : ''Solve the right equation'', berarti sebuah proses untuk memasukkan model simulasi yang tidak pasti dengan melakukan ''benchmarking'' dari data eksperimental. Apabila kondisi memenuhi, maka besaran dan tanda akan menyesuaikan error secara sendirinya dalam melakukan simulasi. Dalam prosedur ini dasarnya adalah melakukan pemastian hitungan dengan memberikan beberapa jangkauan kondisi fisik dari sistem yang didapatkan berasarkan perhitungan dan dibandingkan dengan hasil simulasi numerikal dalam beragam kondisi. Dari perbandingan terhadap kondsisi eksperimental ini, dapat terlihat seberapa jauh kesalahan yang terjadi.<br />
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'''Verifikasi''' : ''Solve the equation right'', berarti sebuah proses untuk memasukkan simulasi numerikal yang tidak pasti dan apabila sesuai, memastikan besaran dan tanda dari error simulasi tersebut serta ketidakpastiannya. Pada bagian ini dasarnya adalah memastikan parameter yang digunakan pada saat dilakukan simulasi. Hal ini juga perlu diperhatikan besar mesh yang digunakan serta time-step yang terjadi, apakah sesuai atau tidak dalam dilakukan perhitungan tersebut.<br />
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== Analisis CFD dalam Simulasi Cyclone Seperator ==<br />
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'''Validasi'''<br />
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[[File:GeomPaperAles.jpg|400px|center]]<br />
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Pada kasus ini, dilakukan benchmarking berdasarkan paper ''Numerical Analysis of Gas-Solid Behavior in a Cyclone Separator for Circulating Fluidized Bed System'' (DOI:10.18869/acadpub.jafm.73.241.26951). Paper ini memberikan contoh ''property'' dari partikel solid berupa pasir dengan jangkauan diameter per partikel sekitar 100-425 µm dan kecepatan aliran pada bagian inlet sekitar 16 m/s. Alat ini pada dasarnya bekerja dengan memasukkan gas-solid pada bagian inlet dari sistem tersebut secara tangensial. Percepatan kemudian terbentuk secara ''helical'' karena bentuk dinding yang berupa ''cone''. Partikel yang lebih berat akan cenderung jatuh ke bawah, yaitu bagian outlet tersebut. Sedangkan, partikel yang lebih kecil lagi (seperti udara) akan mengalir mengarah bagian tengah dan mengarah ke ''vortex finder'' dari sistem tersebut. Hal ini akan membuat udara tersebut keluar pada bagian outlet di atas sistem.<br />
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[[File:RSMTransportEqAles.jpg|400px|center]]<br />
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Persamaan yang digunakan ini adalah ''transport equation'' untuk Reynolds stress model. Ruas kiri menunjukkan derivasi stress terhadap waktu dan ''convective transport'' pada sistem tersebut. Kemudian, ruas kanan menunjukkan beberapa variabel seperti ''stress diffusion'', ''shear production'', ''pressure-strain'', ''dissipation term'', dan Source ''S'' yang terjadi pada sistem tersebut. Berdasarkan paper ini, interaksi antar particle juga diabaikan untuk dilakukan analisa komputasi yang dilakukan. <br />
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'''Verifikasi'''<br />
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Pada simulasi yang dilakukan, dilakukan dengan kondisi multiphase eulerian-langrangian untuk dilakukan simulasi ini. Kondisi tersebut kemudian dilanjutkan dengan distribusi partikel uniform dengan sekitar 4000 parcel per detiknya selama dua detik. Mesh pada geometri ini pada Δx, Δy, dan Δz, adalah masing-masing 18, 50, dan 21. Distribusi partikel (pasir) diasumsikan ''uniform'' (dengan alasan belum memahami perbedaannya), dengan range diameter seperti yang sudah dijelaskan pada bagian validasi serta kecepatan inlet (pada sumbu z pada geometri ini) dengan sebesar 16 m/s, sesuai dengan kecepatan inlet udara. Pada bagian geometri, inlet diasumsikan udara dengan 1.225 kg/m^3 dengan kecepatan 16 m/s. Bagian outlet atas dan bawah diasumsikan sebagai outflow sehingga udara dapat mengalir pada bagian tersebut. Simulasi yang dilakukan belum banyak dilakukan variasi karena sering terjadi ''error'' pada saat dilakukan simulasi. Setelah dilakukan diagnosa, kesalahan yang terjadi adalah adanya ''adjust time step'' yang dicentang sehingga mengalami ''error'' dan cenderung untuk mengalami software crash pada saat dilakukan. Berikut adalah bukti ''error'' yang terjadi pada saat dilakukan simulasi:<br />
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[[File:CrashAles.jpg|400px|center]]<br />
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[[File:ConvergeFailAles.jpg|300px|center]]<br />
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Hasil ini menunjukkan bahwa sudah dilakukan percobaan dengan kondisi ''adjust time step'' sebagai berikut dengan iterasi tertentu. Kondisi ini menyebabkan adanya crash pada sistem tersebut sehingga tidak bisa dilakukan simulasi dengan kondisi ''adjust time step''. Akan tetapi, dilakukan simulasi kembali dengan kondisi ''boundary conditions'' yang sama namun dengan kondisi ''adjust time step'' yang tidak dilakukan variasi. Hal ini berhasil melakukan simulasi dengan baik, akan tetapi terjadi beberapa permasalahan yang terjadi juga pada kondisi ini.<br />
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'''Diameter Partikel'''<br />
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[[File:CycDWTSAles.jpg|400px|left]]<br />
[[File:ParticleTraceAles.jpg|400px|right]]<br />
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[[File:AlesResidual16.jpg|400px|thumb|center|Residual Perhitungan yang Masih Salah]]<br />
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Gambar berikut menunjukkan hasil yang sudah ditunjukkan tanpa dengan melakukan ''adjust time step''. Terlihat walaupun cukup kecil bahwa adanya partikel (pasir) yang terjatuh ke bagian outflow bawah. Gas atau udara yang bersih seharusnya keluar pada bagian outflow atas, akan tetapi tidak dapat divisualisasikan melalui hasil simulasi yang sudah dilakukan. Time step yang tidak dilakukan penyesuaian pada simulasi tersebut menyebabkan adanya residual untuk ''turbulence'' menjadi sangat besar, sehingga masih banyak sekali kesalahan yang terjadi pada simulasi ini. Tinjauan ini setidaknya masih menunjukkan bahwa partikel tersebut dapat terpisahkan melalui bagian outflow di bawah, walaupun visualisasinya kurang begitu jelas dikarenakan diameter partikel yang relatif sangat kecil. <br />
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'''Tekanan Sistem'''<br />
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[[File:PressGraphY.jpg|400px|center]]<br />
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[[File:CycPressWTSAles.jpg|400px|center]]<br />
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Tekanan yang terjadi ini terlihat melalui visualisasi bahwa kecepatan inlet tersebut menyebabkan adanya tekanan yang besar pada bagian satu sisi dari dinding ''cyclone separator''. Hal ini karena kecepatan yang mendorong dinding tersebut ditambah lagi adanya partikel pasir yang terlibat pada fenomena tersebut. Berdasarkan grafik yang didapatkan juga, terlihat bahwa tekanan cenderung lebih besar pada bagian sisi atas dari sistem tersebut, daripada yang bagian bawah. Seharusnya ada variasi perbedaan terkanan yang terjadi akibat adanya inlet ini, namun dikarenakan simulasi yang begitu terbatas, tidak dapat terlihat secara jelas mengenai grafik tersebut. Bagian outflow atas dan bawah juga tervisualisasi bahwa adanya tekanan yang meningkat akibat adanya aliran tersebut. Perlu adanya beberapa koreksi seperti distribusi partikel yang terjadi pada sistem dan juga mesh yang perlu diperbaiki pada saat dilakukan simulasi.<br />
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'''Evaluasi Pekerjaan'''<br />
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Grafik lainnya tidak menunjukkan hasil yang jelas setelah dilakukan simulasi. Grafik partikel, kecepatan, turbulent, dan lain-lainnya tidak dapat divisualisasikan dengan jelas karena keterbatasan simulasi yang dilakukan. Perlu adanya perhatian yang lebih dalam terkait distribusi partikel tersebut serta visualisasi dari aliran udara, sehingga bisa ditunjukkan terpisahnya jalur udara bersih dan partikel pasir yang ada. Akan tetapi, grafik dan visualisasi yang ditunjukkan tersebut cukup menunjukkan mengenai fenomena multifasa yang terjadi pada sistem ''cyclone separator''. Oleh karena itu, dilakukan perbaikan terkait kesalahan yang terjadi tersebut menjadi lebih baik.<br />
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'''Hasil Evaluasi'''<br />
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Pada simulasi ini, dilakukan pembeda yaitu pada kecepatan inlet dijadikan 5 m/s. Alasan ini masih belum diketahui penyebabnya, namun didapatkan bahwa grafik residunya sudah ''converge'' dan bisa dilakukan pada waktu sekitar 8 detik (sesuai dengan paper). Kondisi pada parcelnya dibedakan menjadi 2000 per second dengan lama waktu selama dua detik. Hal ini ditemukan adanya grafik kecepatan serta visualisasi pada sistem tersebut yang sudah benar. Tekanan sudah terdistribusi dengan baik serta terdapat visualisasi kecepatan yang keluar pada kedua outlet yang menunjukkan adanya udara mengarah ke atas. Grafik juga tersedia sebagai bukti adanya tekanan dan kecepatan yang menunjukkan hasil tersebut. Hasil yang didapatkan adalah sebagai berikut:<br />
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[[File:Residual1Ales.jpg|400px|thumb|center|Hasil Residual pada percobaan dengan v=5 m/s]]<br />
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Pada hasil yang didapatkan, terlihat bahwa partikel yang digambarkan melalui vektor dengan warna bergerak dengan kecepatan yang bervariasi berdasarkan beratnya. Terlihat bahwa partikel tersebut berputar mengitari dinding cyclone dan mengarah ke bawah dalam beberapa detik. Dikarenakan hanya ditetapkan sekitar dua detik untuk masuk sebanyak 2000 parcels per second, maka setelah dua detik, tidak ada lagi partikel yang memasuki sistem tersebut. Setelah itu, terlihat bahwa gerakan partikel mengarah ke outlet di bagian bawah dan seketika tidak terlihat pada visualisasi tersebut. Dapat ditunjukkan bahwa adanya kecepatan inlet tersebut mendorong partikel untuk bergerak secara tangensial dan secara ''helical'' ke bagian outlet. Penggambaran terlihat sebagai berikut:<br />
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[[File:DvectorAles.gif|450px|thumb|center|Vektor Arah Partikel Berdasarkan Ukuran Diameter]]<br />
[[File:VelocityVAles.gif|450px|thumb|center|Vektor Kecepatan Partikel]]<br />
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Distribusi tekanan dan kecepatan terlihat setelah adanya inlet yang masuk dengan besaran tertentu. Pertama melalui tekanan, terlihat bahwa adanya distribusi tekanan yang relatif besar pada bagian atas wall. Ini dikarenakan adanya tekanan dari inlet yang membuat tekanan terpusat di awal dinding tersebut. Kemudian, tekanan tersebut mulai tersebar dengan warna yang mulai berubah sepanjang wall dari ''cyclone'' tersebut. Disini terlihat bahwa persebaran tekanan sebenarnya bergerak juga secara helikal, namun tidak merata sama besarnya karena adanya kecepatan yang cenderung berubah relatif lebih lambat. Kemudian, distribusi kecepatan terlihat bahwa adanya partikel yang awal mulanya mengenai dinding dari inlet tersebut, kemudian tervisualisasi secara gradasi bahwa kecepatan mulai melambat setelah melewati inlet tersebut. Partikel yang jatuh ke bawah terlihat bahwa outlet tersebut menunjukkan adanya partikel yang terjatuh pada bagian itu. Dinding juga ada yang berubah warna menjadi lebih hijau (menandakan kenaikan kecepatan) serta adanya kenaikan kecepatan pada outlet bagian atas. Ini juga menunjukkan bahwa adanya udara yang juga mengarah keatas akibat vortex finder dari sistem. Visualisasi dari simulasi tersebut terlihat di bawah berikut:<br />
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[[File:PressureDisAles.gif|400px|thumb|center|Distribusi Tekanan]]<br />
[[File:VelocityDisAles.gif|400px|thumb|center|Distribusi Kecepatan]]<br />
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Lalu dari hasil grafik, dapat terlihat juga bahwa pada sumbu Z (horizontal pada dinding), tekanan pada bagian tengah cenderung mengecil dan besar pada bagian dekat dinding. Dapat terlihat bahwa tekanan tersebut besar karena adanya partikel yang berputar mengarah ke dinding tersebut. Pada sumbu Y (vertikal terhadap dinding), cenderung membesar pada bagian bawah dan atas juga cukup besar, akan tetapi mengecil juga pada sepanjang titik tengah dari dinding ''cyclone'' tersebut. Kecepatan pada sumbu Z juga terlihat cukup besar (secara magnitude). Dapat ditunjukkan juga bahwa bagian tengah tersebut relatif besar (pada sumbu Z) karena tidak adanya gesekan terhadap dinding sehingga relatif untuk mengalami gerak jatuh bebas. Berbeda dengan yang di dekat dinding, adanya gesekan membuat kecepatan menjadi relatif kecil. Secara sumbu Y, terlihat bahwa adanya kecepatan dengan besaran yang selalu ada. Besarannya berbeda-beda, pengaruh juga dari tekanan yang juga berbeda-beda. Besaran ini mungkin belum tentu akurat (karena adanya faktor error atau mesh), akan tetapi sudah cukup menunjukkan adanya fenomena yang kurang lebih benar terjadi pada sistem ''cyclone separator'' tersebut. Berikut adalah grafik mengenai hasil pada sumbu Z dan Y:<br />
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[[File:GraphZ1.jpg|300px|thumb|center|Grafik pada Sumbu Y (Inlet 5 m/s)]]<br />
[[File:GraphY1Ales.jpg|300px|thumb|center|Grafik pada Sumbu Y (Inlet 5 m/s)]]<br />
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== Sinopsis Tugas Besar Aplikasi CFD ==<br />
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'''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''<br />
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The gas-liquid separator has been widely used in the oil and gas industry to improve product quality. To design and operate the system at a low cost, mathematical modeling becomes very useful. The separator apparatus has three geometrical designs, such as horizontal, vertical, and spherical types, with the horizontal design with the lowest expense in production processes. The horizontal design has three main processes: the separation process, the liquid outlet process, and the gas outlet process. First, the separation process involves a diverter that reduces the gas-liquid velocity and diverts downwards into the separator affected by gravity. Then, the liquid droplets that are larger than a certain size will fall into the separator and continue their flow with a certain amount of liquid at the bottom of the separator to the system's outlet. Finally, the rest of the droplets with a smaller amount of size are considered a gas, which will continue its flow into the upper outlet. The study will use Computational Fluid Dynamics with Multiphase Eulerian-Langrangian method. There will be a variation between a diverter and the flow inlet distance, measured upon its efficiency in separating the gas and the fluid.<br />
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== [[Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator]] ==<br />
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== Referensi Pembelajaran ==<br />
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[1] Versteeg, H.K. and Malalasekera, W., 2007. An introduction to computational fluid dynamics: the finite volume method. Pearson education.<br />
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[2] Tu, J., Yeoh, G.H. and Liu, C., 2018. Computational fluid dynamics: a practical approach. Butterworth-Heinemann.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=54920TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-13T08:23:45Z<p>Alesdaniel: /* Presentation Video */</p>
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<div>== Abstract ==<br />
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Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
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'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
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== Introduction ==<br />
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Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
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[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
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== Objectives ==<br />
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In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
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1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
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2. To investigate the most efficient separator within several distances from the inlet.<br />
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3. To investigate the suitable separator with and without a perforated separator.<br />
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== Numerical Geometry ==<br />
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The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
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[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
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The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
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[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
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== Methodology ==<br />
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=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
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=== Mathematical Model (Verification) ===<br />
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The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
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[[File:GovEq.jpg|500px|thumb|center]]<br />
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These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
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[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Distances !! scope="col" | Efficiency<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.<br />
<br />
<br />
<br />
==Presentation Video ==<br />
<br />
[https://youtu.be/RGMBDP4__34 Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator - UAS CFD (Ales Daniel/1706036072)]</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=54917TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-13T08:21:27Z<p>Alesdaniel: /* Presentation Video */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Distances !! scope="col" | Efficiency<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.<br />
<br />
<br />
<br />
==Presentation Video ==<br />
<br />
[https://youtu.be/RGMBDP4__34 link title]</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=54916TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-13T08:20:17Z<p>Alesdaniel: /* Presentation Video */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Distances !! scope="col" | Efficiency<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.<br />
<br />
<br />
<br />
==Presentation Video ==<br />
<br />
[https://youtu.be/RGMBDP4__34 Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator - UAS CFD (Ales Daniel/1706036072)]</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=54877TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-13T07:21:08Z<p>Alesdaniel: /* Objectives */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Distances !! scope="col" | Efficiency<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.<br />
<br />
<br />
<br />
==Presentation Video ==<br />
<br />
[http://www.example.com link title]</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=54732TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-12T12:13:07Z<p>Alesdaniel: /* Separator Distance Variations */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Distances !! scope="col" | Efficiency<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.<br />
<br />
<br />
<br />
==Presentation Video ==<br />
<br />
[http://www.example.com link title]</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=54712TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-12T08:48:57Z<p>Alesdaniel: /* Results and Discussions */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.<br />
<br />
<br />
<br />
==Presentation Video ==<br />
<br />
[http://www.example.com link title]</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=54694TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-12T07:37:04Z<p>Alesdaniel: /* Presentation Video */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.<br />
<br />
<br />
<br />
==Presentation Video ==<br />
<br />
[http://www.example.com link title]</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=54693TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-12T07:36:04Z<p>Alesdaniel: </p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.<br />
<br />
<br />
<br />
== Presentation Video ==</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=Ales_Daniel_-_1706036072&diff=54692Ales Daniel - 17060360722021-01-12T07:34:23Z<p>Alesdaniel: /* Volume of Fluid (VoF) */</p>
<hr />
<div>[[File:alesdaniel.JPG|500px|thumb|center|Hello! Welcome to my page. My name is Ales and I'm pleased that you've visited my page. Enjoy!]]<br />
<br />
<br />
<br />
== ''Governing Equations'' Aliran Fluida ==<br />
<br />
Sebelum melakukan perhitungan pada aliran fluida dan perpindahan kalor, ada beberapa prinsip dasar yang perlu diperhatikan, yaitu konservasi massa (kontinuitas), momentum, dan energi. Pada dasarnya, berlaku hukum konservasi pada fisika dengan beberapa penjelasan sebagai berikut:<br />
1. Massa dari fluida dikonservasi<br />
2. Perubahan momentum sama dengan jumlah gaya yang terjadi pada partikel fluida (Hukum Kedua Newton)<br />
3. Perubahan energi sama dengan jumlah penambahan energi dan kerja yang diberikan pada partikel fluida (Hukum Pertama Termodinamika)<br />
<br />
Fluida tersebut akan dianggap sebagai sebuah ''continuum''. Pada saat melakukan analisa dari sistem tersebut, struktur dan gerakan molekuler dapat kita abaikan pada saat melakukan analisa. Fluida dapat kita asumsikan sebagai sebuah hal yang berukuran makroskopik seperti kecepatan, tekanan, massa jenis, temperatur, ruangnya, beserta perubahan waktunya. Semua fluida pada saat dilakukan perhitungan dianggap sebagai sebuah fungsi waktu dan ruang dengan beberapa sifat-sifat tertentu yang perlu ditinjau. Persamaan secara keseluruhan yang sudah dilakukan penurunan adalah sebagai berikut:<br />
<br />
[[File:GovEqAles.jpg|600px|thumb|center|''Governing Equations'' Aliran Fluida]]<br />
<br />
== Tugas Penurunan Rumus Kontinuitas dan Momentum ==<br />
<br />
[https://www.youtube.com/watch?v=VeYVEZfdr9E&list=PLLbF6f_08EZstokisa-DcZuPiqDqS6ZjZ&index=4&t=1s Video Penurunan Rumus dan Simulasi CFDSof]<br />
<br />
<br />
== Konveksi-Difusi dan Kuis Difusi ==<br />
<br />
[https://www.youtube.com/watch?v=YjAouwbj98Y&list=PLLbF6f_08EZu7yDcpOk69V07OwrlijX61&index=2&t=440s Video FVM for Diffusion]<br />
<br />
== SIMPLE Method ==<br />
<br />
Pada kelas terakhir (22 Oktober 2020) dijelaskan bahwa dengan metode staggered grid, kita dapat melakukan pembagian perhitungan berdasarkan control volume tertentu dan dibagi berdasarkan variabel skalar atau vektor. Salah satu metode yang digunakan adalah SIMPLE. Metode ini melakukan guessing atau menebak sebuah variabel tertentu yang ingin dicari pada sebuah permasalahan. Variabel tersebut kemudian dilakukan diskritisasi momentum dan persamaan pressure. Setelah dilakukan perhitungan, dapat dilakukan correction dengan menghitung deviasi yang terjadi pada perhitungan tersebut. Tentunya, diperlukan juga kondisi under-relaxation factor, untuk mengurangi kemungkinan perhitungan iterasi menjadi divergence. Angka tersebut apabila menggunakan besaran yang tepat, dapat menghasilkan simulasi yang cukup efektif dengan hasil convergence. Kalau terlalu besar, akan menghasilkan ketidakseimbangan perhitungan yang berujung pada divergence pada iterasi yang dilakukan.<br />
<br />
[[File:SIMPLEAles.jpg|400px|thumb|center|Algoritma dari SIMPLE]]<br />
<br />
== 6Dof and Dynamic Mesh ==<br />
<br />
''Six degrees of freedom'' merupakan sebuah gerakan dari objek yang bisa bergerak secara tiga dimensi, terukur dari titik ''center of gravity''-nya atau CoG. Pada simulasi menggunakan CFD, sebuah fluida yang mengalir akan bergerak secara translasi dan rotasi. Translasi terukur berdasarkan perubahan kecepatan terhadap perubahan waktu, atau secara rumus merupakan '''SygmaF = massa x akselerasi''', dimana total gaya yang dihasilkan berdasarkan perubahan massa sebuah objek terhadap perpindahan benda yang berubah terhadap waktu. Sedangkan kalau berdasarkan rotasi, terukur dengan istilah ''angular velocity'' berdasarkan torsi terhadap momen inersia dari objek yang terukur. Rumus yang digunakan adalah '''SygmaMoment = Moment Inertia x Akselerasi angular'''.<br />
<br />
Berdasarkan ini, simulasi yang dilakukan pada CFD Solver akan digunakan untuk ''Dynamic Mesh''. Pada kasus fluida yang mengalir dalam sistem apapun, CFD akan melakukan perhitungan berdasarkan posisi yang berubah baik secara translasi maupun rotasi secara metode komputasi. Mesh tersebut akan berubah-ubah sesuai dengan gaya yang bekerja pada sistem tertentu. Pada topik ini, diberikan contoh simulasi berupa ''Vertical-Axis Wind Turbine'', yang ditunjukkan dari tampak atas untuk mengetahui fenomena yang terjadi. Simulasi dilakukan dua kali dengan dua kondisi yang dimodifikasi berbeda. Kondisi yang diubah ditunjukkan berdasarkan data sebagai berikut:<br />
<br />
1.<br />
<br />
Control Dict<br />
<br />
- Max Delta T : 0.01<br />
<br />
- End Time 10<br />
<br />
<br />
Dynamic Mesh Dict<br />
<br />
- //g (0 9.8 0);<br />
<br />
// :: lOD :: angularMomentum (default = (0 10 0))<br />
<br />
<br />
2.<br />
<br />
Control Dict<br />
<br />
- Max Delta T : 0.01<br />
<br />
- End Time 10<br />
<br />
Dynamic Mesh Dict<br />
<br />
- //g (0 9.8 0);<br />
<br />
// :: lOD :: angularMomentum (default = (0 100 0))<br />
<br />
//- Angular momentum of the rigid-body in local reference frame<br />
<br />
angularMomentum (10 10 10);<br />
<br />
<br />
Hasil yang didapatkan adalah berdasarkan gambar sebagai berikut:<br />
<br />
1. Hasil simulasi 1<br />
<br />
[[File:VAWT Ales1.jpg|500px|center]]<br />
<br />
<br />
<br />
2. Hasil simulasi 2<br />
<br />
[[File:VAWT Ales2.jpg|500px|center]]<br />
<br />
<br />
== Economizer Hopper (CFDSof Simulation) ==<br />
<br />
Economizer Hopper merupakan alat untuk mengatasi permasalahan akibat ''fly ash'' yang berasal dari produk pembakaran batubara. Potensi yang mungkin terjadi adalah penumpukan ''fly ash'' pada economizer ''flue gas ducting'', ''blocking'' abu di elemen pre-air heater, serta pengikisan pada blade dan ''guide vane''. Dengan adanya modifikasi Hopper tersebut, abu atau ''fly ash'' yang dialirkan saat keluar dari Boiler akan tertampung pada bagian ''bottom ash'' tersebut. <br />
<br />
Pada kasus ini, dilakukan simulasi menggunakan CFDSof dengan melakukan pembeda antara economizer dengan hopper dan tidak. Analisa yang dilakukan adalah dengan simulasi secara ''transient'', kemudian dilakukan simulasi multifasa dengan pendekatan ''eulerian-langrangian'', dengan fasa padatan dalam bentuk ''fly ash'' serta liquid dalam bentuk gas yang mengalir pada sistem tersebut. <br />
<br />
Hasil dari simulasi tersebut digambarkan melalui dokumentasi yang sudah dibagi berdasarkan beberapa tinjauan sebagai berikut:<br />
<br />
<br />
<br />
'''Analisa diameter partikel'''<br />
<br />
1. Tanpa Hopper<br />
<br />
<br />
[[File:EconomizerTanpaHopper.gif|center|400px]]<br />
<br />
[[File:Ales_ETH_Iso.gif|center|400px]]<br />
<br />
<br />
<br />
2. Dengan Hopper<br />
<br />
[[File:Ales_EH.gif|center|400px]]<br />
<br />
[[File:Ales_EH_Iso.gif|center|400px]]<br />
<br />
<br />
Melalui hasil ini, dapat disimpulkan bahwa dengan penggunaan hopper, mampu menangkap partikel ''fly ash'' pada wadah tertentu. Simulasi yang dilakukan dapat terlihat dari partikel berwarna merah yang mampu ditampung pada wadah tertentu saat melalui jalur tersebut. Partikel dengan ukuran yang lebih kecil, cenderung dapat melanjutkan sampai ke bagian outlet dari economizer hopper tersebut.<br />
<br />
<br />
----<br />
<br />
'''Analisa tekanan sistem'''<br />
<br />
<br />
[[File:Pressure_Econo_Ales.gif|center|400px]]<br />
<br />
<br />
Pada hasil dari kedua simulasi tersebut, dapat terlihat bahwa tekanan pada bagian ''outflow'' semakin besar daripada bagian inlet dari sistem untuk kedua hasil uji coba. Hasil ini dikarenakan adanya perbedaan ketinggian yang terjadi sembari berjalannya ''fly ash'' kepada arah outflow tersebut. Tekanan ini diakibatkan karena adanya kecepatan di bagian inlet yang juga bisa mempengaruhi tekanan pada outlet tersebut. Tekanan ini terjadi pada sistem tersebut dan dapat mempengaruhi partikel yang bergerak melalui sistem tersebut. Pengaruh yang terjadi adalah kecepatan sistem tersebut untuk bergerak sepanjang sistem yang akan cenderung lebih cepat seiring dalam semakin besarnya tekanan pada sistem.<br />
<br />
----<br />
<br />
'''Analisa kecepatan sistem'''<br />
<br />
[[File:Velocity_Econo_Ales.gif|center|400px]]<br />
<br />
Partikel tersebut akan bergerak terus menerus dan ada yang diakibatkan oleh kesetimbangan gaya (''bouyancy''), sehingga beberapa partikel bergerak dengan kecepatan yang berbeda. Partikel dengan massa yang lebih besar akan cenderung lebih dahulu, sedangkan yang tidak akan lebih mengalami gaya apung di dalam sistem tersebut. Dapat terlihat bahwa partikel dengan massa yang lebih berat (berdasarkan diameter) lebih dahulu menyentuh hopper (pada bagian dengan ada hopper) dan terjebak di dalam hopper tersebut. Sedangkan untuk yang lebih ringan, dengan kecepatan yang lebih pelan, akan cenderung mengapung dan masih ada kemungkinan bergerak ke bagian outlet dari sistem tersebut.<br />
<br />
== Validasi dan Verifikasi ==<br />
<br />
Validasi dan verifikasi menjadi salah satu langkah untuk melakukan simulasi CFD dengan secara kuantitatif mengestimasi error yang tetap serta ketidakpastian dalam simulasi numerikal. Walaupun keduanya memiliki definisi yang cukup dekat, kedua ini berdasarkan AIAA Guide (1998) menjadi dua hal yang sangat berbeda. <br />
<br />
'''Validasi''' : ''Solve the right equation'', berarti sebuah proses untuk memasukkan model simulasi yang tidak pasti dengan melakukan ''benchmarking'' dari data eksperimental. Apabila kondisi memenuhi, maka besaran dan tanda akan menyesuaikan error secara sendirinya dalam melakukan simulasi. Dalam prosedur ini dasarnya adalah melakukan pemastian hitungan dengan memberikan beberapa jangkauan kondisi fisik dari sistem yang didapatkan berasarkan perhitungan dan dibandingkan dengan hasil simulasi numerikal dalam beragam kondisi. Dari perbandingan terhadap kondsisi eksperimental ini, dapat terlihat seberapa jauh kesalahan yang terjadi.<br />
<br />
'''Verifikasi''' : ''Solve the equation right'', berarti sebuah proses untuk memasukkan simulasi numerikal yang tidak pasti dan apabila sesuai, memastikan besaran dan tanda dari error simulasi tersebut serta ketidakpastiannya. Pada bagian ini dasarnya adalah memastikan parameter yang digunakan pada saat dilakukan simulasi. Hal ini juga perlu diperhatikan besar mesh yang digunakan serta time-step yang terjadi, apakah sesuai atau tidak dalam dilakukan perhitungan tersebut.<br />
<br />
== Analisis CFD dalam Simulasi Cyclone Seperator ==<br />
<br />
'''Validasi'''<br />
<br />
[[File:GeomPaperAles.jpg|400px|center]]<br />
<br />
Pada kasus ini, dilakukan benchmarking berdasarkan paper ''Numerical Analysis of Gas-Solid Behavior in a Cyclone Separator for Circulating Fluidized Bed System'' (DOI:10.18869/acadpub.jafm.73.241.26951). Paper ini memberikan contoh ''property'' dari partikel solid berupa pasir dengan jangkauan diameter per partikel sekitar 100-425 µm dan kecepatan aliran pada bagian inlet sekitar 16 m/s. Alat ini pada dasarnya bekerja dengan memasukkan gas-solid pada bagian inlet dari sistem tersebut secara tangensial. Percepatan kemudian terbentuk secara ''helical'' karena bentuk dinding yang berupa ''cone''. Partikel yang lebih berat akan cenderung jatuh ke bawah, yaitu bagian outlet tersebut. Sedangkan, partikel yang lebih kecil lagi (seperti udara) akan mengalir mengarah bagian tengah dan mengarah ke ''vortex finder'' dari sistem tersebut. Hal ini akan membuat udara tersebut keluar pada bagian outlet di atas sistem.<br />
<br />
<br />
[[File:RSMTransportEqAles.jpg|400px|center]]<br />
<br />
Persamaan yang digunakan ini adalah ''transport equation'' untuk Reynolds stress model. Ruas kiri menunjukkan derivasi stress terhadap waktu dan ''convective transport'' pada sistem tersebut. Kemudian, ruas kanan menunjukkan beberapa variabel seperti ''stress diffusion'', ''shear production'', ''pressure-strain'', ''dissipation term'', dan Source ''S'' yang terjadi pada sistem tersebut. Berdasarkan paper ini, interaksi antar particle juga diabaikan untuk dilakukan analisa komputasi yang dilakukan. <br />
<br />
<br />
----<br />
'''Verifikasi'''<br />
<br />
Pada simulasi yang dilakukan, dilakukan dengan kondisi multiphase eulerian-langrangian untuk dilakukan simulasi ini. Kondisi tersebut kemudian dilanjutkan dengan distribusi partikel uniform dengan sekitar 4000 parcel per detiknya selama dua detik. Mesh pada geometri ini pada Δx, Δy, dan Δz, adalah masing-masing 18, 50, dan 21. Distribusi partikel (pasir) diasumsikan ''uniform'' (dengan alasan belum memahami perbedaannya), dengan range diameter seperti yang sudah dijelaskan pada bagian validasi serta kecepatan inlet (pada sumbu z pada geometri ini) dengan sebesar 16 m/s, sesuai dengan kecepatan inlet udara. Pada bagian geometri, inlet diasumsikan udara dengan 1.225 kg/m^3 dengan kecepatan 16 m/s. Bagian outlet atas dan bawah diasumsikan sebagai outflow sehingga udara dapat mengalir pada bagian tersebut. Simulasi yang dilakukan belum banyak dilakukan variasi karena sering terjadi ''error'' pada saat dilakukan simulasi. Setelah dilakukan diagnosa, kesalahan yang terjadi adalah adanya ''adjust time step'' yang dicentang sehingga mengalami ''error'' dan cenderung untuk mengalami software crash pada saat dilakukan. Berikut adalah bukti ''error'' yang terjadi pada saat dilakukan simulasi:<br />
<br />
<br />
[[File:CrashAles.jpg|400px|center]]<br />
<br />
[[File:ConvergeFailAles.jpg|300px|center]]<br />
<br />
<br />
<br />
Hasil ini menunjukkan bahwa sudah dilakukan percobaan dengan kondisi ''adjust time step'' sebagai berikut dengan iterasi tertentu. Kondisi ini menyebabkan adanya crash pada sistem tersebut sehingga tidak bisa dilakukan simulasi dengan kondisi ''adjust time step''. Akan tetapi, dilakukan simulasi kembali dengan kondisi ''boundary conditions'' yang sama namun dengan kondisi ''adjust time step'' yang tidak dilakukan variasi. Hal ini berhasil melakukan simulasi dengan baik, akan tetapi terjadi beberapa permasalahan yang terjadi juga pada kondisi ini.<br />
<br />
<br />
----<br />
<br />
'''Diameter Partikel'''<br />
<br />
[[File:CycDWTSAles.jpg|400px|left]]<br />
[[File:ParticleTraceAles.jpg|400px|right]]<br />
<br />
[[File:AlesResidual16.jpg|400px|thumb|center|Residual Perhitungan yang Masih Salah]]<br />
<br />
Gambar berikut menunjukkan hasil yang sudah ditunjukkan tanpa dengan melakukan ''adjust time step''. Terlihat walaupun cukup kecil bahwa adanya partikel (pasir) yang terjatuh ke bagian outflow bawah. Gas atau udara yang bersih seharusnya keluar pada bagian outflow atas, akan tetapi tidak dapat divisualisasikan melalui hasil simulasi yang sudah dilakukan. Time step yang tidak dilakukan penyesuaian pada simulasi tersebut menyebabkan adanya residual untuk ''turbulence'' menjadi sangat besar, sehingga masih banyak sekali kesalahan yang terjadi pada simulasi ini. Tinjauan ini setidaknya masih menunjukkan bahwa partikel tersebut dapat terpisahkan melalui bagian outflow di bawah, walaupun visualisasinya kurang begitu jelas dikarenakan diameter partikel yang relatif sangat kecil. <br />
<br />
<br />
'''Tekanan Sistem'''<br />
<br />
[[File:PressGraphY.jpg|400px|center]]<br />
<br />
[[File:CycPressWTSAles.jpg|400px|center]]<br />
<br />
<br />
Tekanan yang terjadi ini terlihat melalui visualisasi bahwa kecepatan inlet tersebut menyebabkan adanya tekanan yang besar pada bagian satu sisi dari dinding ''cyclone separator''. Hal ini karena kecepatan yang mendorong dinding tersebut ditambah lagi adanya partikel pasir yang terlibat pada fenomena tersebut. Berdasarkan grafik yang didapatkan juga, terlihat bahwa tekanan cenderung lebih besar pada bagian sisi atas dari sistem tersebut, daripada yang bagian bawah. Seharusnya ada variasi perbedaan terkanan yang terjadi akibat adanya inlet ini, namun dikarenakan simulasi yang begitu terbatas, tidak dapat terlihat secara jelas mengenai grafik tersebut. Bagian outflow atas dan bawah juga tervisualisasi bahwa adanya tekanan yang meningkat akibat adanya aliran tersebut. Perlu adanya beberapa koreksi seperti distribusi partikel yang terjadi pada sistem dan juga mesh yang perlu diperbaiki pada saat dilakukan simulasi.<br />
<br />
<br />
<br />
'''Evaluasi Pekerjaan'''<br />
<br />
Grafik lainnya tidak menunjukkan hasil yang jelas setelah dilakukan simulasi. Grafik partikel, kecepatan, turbulent, dan lain-lainnya tidak dapat divisualisasikan dengan jelas karena keterbatasan simulasi yang dilakukan. Perlu adanya perhatian yang lebih dalam terkait distribusi partikel tersebut serta visualisasi dari aliran udara, sehingga bisa ditunjukkan terpisahnya jalur udara bersih dan partikel pasir yang ada. Akan tetapi, grafik dan visualisasi yang ditunjukkan tersebut cukup menunjukkan mengenai fenomena multifasa yang terjadi pada sistem ''cyclone separator''. Oleh karena itu, dilakukan perbaikan terkait kesalahan yang terjadi tersebut menjadi lebih baik.<br />
<br />
<br />
'''Hasil Evaluasi'''<br />
<br />
Pada simulasi ini, dilakukan pembeda yaitu pada kecepatan inlet dijadikan 5 m/s. Alasan ini masih belum diketahui penyebabnya, namun didapatkan bahwa grafik residunya sudah ''converge'' dan bisa dilakukan pada waktu sekitar 8 detik (sesuai dengan paper). Kondisi pada parcelnya dibedakan menjadi 2000 per second dengan lama waktu selama dua detik. Hal ini ditemukan adanya grafik kecepatan serta visualisasi pada sistem tersebut yang sudah benar. Tekanan sudah terdistribusi dengan baik serta terdapat visualisasi kecepatan yang keluar pada kedua outlet yang menunjukkan adanya udara mengarah ke atas. Grafik juga tersedia sebagai bukti adanya tekanan dan kecepatan yang menunjukkan hasil tersebut. Hasil yang didapatkan adalah sebagai berikut:<br />
<br />
[[File:Residual1Ales.jpg|400px|thumb|center|Hasil Residual pada percobaan dengan v=5 m/s]]<br />
<br />
Pada hasil yang didapatkan, terlihat bahwa partikel yang digambarkan melalui vektor dengan warna bergerak dengan kecepatan yang bervariasi berdasarkan beratnya. Terlihat bahwa partikel tersebut berputar mengitari dinding cyclone dan mengarah ke bawah dalam beberapa detik. Dikarenakan hanya ditetapkan sekitar dua detik untuk masuk sebanyak 2000 parcels per second, maka setelah dua detik, tidak ada lagi partikel yang memasuki sistem tersebut. Setelah itu, terlihat bahwa gerakan partikel mengarah ke outlet di bagian bawah dan seketika tidak terlihat pada visualisasi tersebut. Dapat ditunjukkan bahwa adanya kecepatan inlet tersebut mendorong partikel untuk bergerak secara tangensial dan secara ''helical'' ke bagian outlet. Penggambaran terlihat sebagai berikut:<br />
<br />
[[File:DvectorAles.gif|450px|thumb|center|Vektor Arah Partikel Berdasarkan Ukuran Diameter]]<br />
[[File:VelocityVAles.gif|450px|thumb|center|Vektor Kecepatan Partikel]]<br />
<br />
Distribusi tekanan dan kecepatan terlihat setelah adanya inlet yang masuk dengan besaran tertentu. Pertama melalui tekanan, terlihat bahwa adanya distribusi tekanan yang relatif besar pada bagian atas wall. Ini dikarenakan adanya tekanan dari inlet yang membuat tekanan terpusat di awal dinding tersebut. Kemudian, tekanan tersebut mulai tersebar dengan warna yang mulai berubah sepanjang wall dari ''cyclone'' tersebut. Disini terlihat bahwa persebaran tekanan sebenarnya bergerak juga secara helikal, namun tidak merata sama besarnya karena adanya kecepatan yang cenderung berubah relatif lebih lambat. Kemudian, distribusi kecepatan terlihat bahwa adanya partikel yang awal mulanya mengenai dinding dari inlet tersebut, kemudian tervisualisasi secara gradasi bahwa kecepatan mulai melambat setelah melewati inlet tersebut. Partikel yang jatuh ke bawah terlihat bahwa outlet tersebut menunjukkan adanya partikel yang terjatuh pada bagian itu. Dinding juga ada yang berubah warna menjadi lebih hijau (menandakan kenaikan kecepatan) serta adanya kenaikan kecepatan pada outlet bagian atas. Ini juga menunjukkan bahwa adanya udara yang juga mengarah keatas akibat vortex finder dari sistem. Visualisasi dari simulasi tersebut terlihat di bawah berikut:<br />
<br />
[[File:PressureDisAles.gif|400px|thumb|center|Distribusi Tekanan]]<br />
[[File:VelocityDisAles.gif|400px|thumb|center|Distribusi Kecepatan]]<br />
<br />
<br />
Lalu dari hasil grafik, dapat terlihat juga bahwa pada sumbu Z (horizontal pada dinding), tekanan pada bagian tengah cenderung mengecil dan besar pada bagian dekat dinding. Dapat terlihat bahwa tekanan tersebut besar karena adanya partikel yang berputar mengarah ke dinding tersebut. Pada sumbu Y (vertikal terhadap dinding), cenderung membesar pada bagian bawah dan atas juga cukup besar, akan tetapi mengecil juga pada sepanjang titik tengah dari dinding ''cyclone'' tersebut. Kecepatan pada sumbu Z juga terlihat cukup besar (secara magnitude). Dapat ditunjukkan juga bahwa bagian tengah tersebut relatif besar (pada sumbu Z) karena tidak adanya gesekan terhadap dinding sehingga relatif untuk mengalami gerak jatuh bebas. Berbeda dengan yang di dekat dinding, adanya gesekan membuat kecepatan menjadi relatif kecil. Secara sumbu Y, terlihat bahwa adanya kecepatan dengan besaran yang selalu ada. Besarannya berbeda-beda, pengaruh juga dari tekanan yang juga berbeda-beda. Besaran ini mungkin belum tentu akurat (karena adanya faktor error atau mesh), akan tetapi sudah cukup menunjukkan adanya fenomena yang kurang lebih benar terjadi pada sistem ''cyclone separator'' tersebut. Berikut adalah grafik mengenai hasil pada sumbu Z dan Y:<br />
<br />
<br />
[[File:GraphZ1.jpg|300px|thumb|center|Grafik pada Sumbu Y (Inlet 5 m/s)]]<br />
[[File:GraphY1Ales.jpg|300px|thumb|center|Grafik pada Sumbu Y (Inlet 5 m/s)]]<br />
<br />
== Sinopsis Tugas Besar Aplikasi CFD ==<br />
<br />
<br />
'''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''<br />
<br />
The gas-liquid separator has been widely used in the oil and gas industry to improve product quality. To design and operate the system at a low cost, mathematical modeling becomes very useful. The separator apparatus has three geometrical designs, such as horizontal, vertical, and spherical types, with the horizontal design with the lowest expense in production processes. The horizontal design has three main processes: the separation process, the liquid outlet process, and the gas outlet process. First, the separation process involves a diverter that reduces the gas-liquid velocity and diverts downwards into the separator affected by gravity. Then, the liquid droplets that are larger than a certain size will fall into the separator and continue their flow with a certain amount of liquid at the bottom of the separator to the system's outlet. Finally, the rest of the droplets with a smaller amount of size are considered a gas, which will continue its flow into the upper outlet. The study will use Computational Fluid Dynamics with Multiphase Eulerian-Langrangian method. There will be a variation between a diverter and the flow inlet distance, measured upon its efficiency in separating the gas and the fluid.<br />
<br />
== [[TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator''']] ==<br />
<br />
== Referensi Pembelajaran ==<br />
<br />
<br />
[1] Versteeg, H.K. and Malalasekera, W., 2007. An introduction to computational fluid dynamics: the finite volume method. Pearson education.<br />
<br />
[2] Tu, J., Yeoh, G.H. and Liu, C., 2018. Computational fluid dynamics: a practical approach. Butterworth-Heinemann.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=Ales_Daniel_-_1706036072&diff=54691Ales Daniel - 17060360722021-01-12T07:33:47Z<p>Alesdaniel: /* Unsteady Flow */</p>
<hr />
<div>[[File:alesdaniel.JPG|500px|thumb|center|Hello! Welcome to my page. My name is Ales and I'm pleased that you've visited my page. Enjoy!]]<br />
<br />
<br />
<br />
== ''Governing Equations'' Aliran Fluida ==<br />
<br />
Sebelum melakukan perhitungan pada aliran fluida dan perpindahan kalor, ada beberapa prinsip dasar yang perlu diperhatikan, yaitu konservasi massa (kontinuitas), momentum, dan energi. Pada dasarnya, berlaku hukum konservasi pada fisika dengan beberapa penjelasan sebagai berikut:<br />
1. Massa dari fluida dikonservasi<br />
2. Perubahan momentum sama dengan jumlah gaya yang terjadi pada partikel fluida (Hukum Kedua Newton)<br />
3. Perubahan energi sama dengan jumlah penambahan energi dan kerja yang diberikan pada partikel fluida (Hukum Pertama Termodinamika)<br />
<br />
Fluida tersebut akan dianggap sebagai sebuah ''continuum''. Pada saat melakukan analisa dari sistem tersebut, struktur dan gerakan molekuler dapat kita abaikan pada saat melakukan analisa. Fluida dapat kita asumsikan sebagai sebuah hal yang berukuran makroskopik seperti kecepatan, tekanan, massa jenis, temperatur, ruangnya, beserta perubahan waktunya. Semua fluida pada saat dilakukan perhitungan dianggap sebagai sebuah fungsi waktu dan ruang dengan beberapa sifat-sifat tertentu yang perlu ditinjau. Persamaan secara keseluruhan yang sudah dilakukan penurunan adalah sebagai berikut:<br />
<br />
[[File:GovEqAles.jpg|600px|thumb|center|''Governing Equations'' Aliran Fluida]]<br />
<br />
== Tugas Penurunan Rumus Kontinuitas dan Momentum ==<br />
<br />
[https://www.youtube.com/watch?v=VeYVEZfdr9E&list=PLLbF6f_08EZstokisa-DcZuPiqDqS6ZjZ&index=4&t=1s Video Penurunan Rumus dan Simulasi CFDSof]<br />
<br />
<br />
== Konveksi-Difusi dan Kuis Difusi ==<br />
<br />
[https://www.youtube.com/watch?v=YjAouwbj98Y&list=PLLbF6f_08EZu7yDcpOk69V07OwrlijX61&index=2&t=440s Video FVM for Diffusion]<br />
<br />
== SIMPLE Method ==<br />
<br />
Pada kelas terakhir (22 Oktober 2020) dijelaskan bahwa dengan metode staggered grid, kita dapat melakukan pembagian perhitungan berdasarkan control volume tertentu dan dibagi berdasarkan variabel skalar atau vektor. Salah satu metode yang digunakan adalah SIMPLE. Metode ini melakukan guessing atau menebak sebuah variabel tertentu yang ingin dicari pada sebuah permasalahan. Variabel tersebut kemudian dilakukan diskritisasi momentum dan persamaan pressure. Setelah dilakukan perhitungan, dapat dilakukan correction dengan menghitung deviasi yang terjadi pada perhitungan tersebut. Tentunya, diperlukan juga kondisi under-relaxation factor, untuk mengurangi kemungkinan perhitungan iterasi menjadi divergence. Angka tersebut apabila menggunakan besaran yang tepat, dapat menghasilkan simulasi yang cukup efektif dengan hasil convergence. Kalau terlalu besar, akan menghasilkan ketidakseimbangan perhitungan yang berujung pada divergence pada iterasi yang dilakukan.<br />
<br />
[[File:SIMPLEAles.jpg|400px|thumb|center|Algoritma dari SIMPLE]]<br />
<br />
== 6Dof and Dynamic Mesh ==<br />
<br />
''Six degrees of freedom'' merupakan sebuah gerakan dari objek yang bisa bergerak secara tiga dimensi, terukur dari titik ''center of gravity''-nya atau CoG. Pada simulasi menggunakan CFD, sebuah fluida yang mengalir akan bergerak secara translasi dan rotasi. Translasi terukur berdasarkan perubahan kecepatan terhadap perubahan waktu, atau secara rumus merupakan '''SygmaF = massa x akselerasi''', dimana total gaya yang dihasilkan berdasarkan perubahan massa sebuah objek terhadap perpindahan benda yang berubah terhadap waktu. Sedangkan kalau berdasarkan rotasi, terukur dengan istilah ''angular velocity'' berdasarkan torsi terhadap momen inersia dari objek yang terukur. Rumus yang digunakan adalah '''SygmaMoment = Moment Inertia x Akselerasi angular'''.<br />
<br />
Berdasarkan ini, simulasi yang dilakukan pada CFD Solver akan digunakan untuk ''Dynamic Mesh''. Pada kasus fluida yang mengalir dalam sistem apapun, CFD akan melakukan perhitungan berdasarkan posisi yang berubah baik secara translasi maupun rotasi secara metode komputasi. Mesh tersebut akan berubah-ubah sesuai dengan gaya yang bekerja pada sistem tertentu. Pada topik ini, diberikan contoh simulasi berupa ''Vertical-Axis Wind Turbine'', yang ditunjukkan dari tampak atas untuk mengetahui fenomena yang terjadi. Simulasi dilakukan dua kali dengan dua kondisi yang dimodifikasi berbeda. Kondisi yang diubah ditunjukkan berdasarkan data sebagai berikut:<br />
<br />
1.<br />
<br />
Control Dict<br />
<br />
- Max Delta T : 0.01<br />
<br />
- End Time 10<br />
<br />
<br />
Dynamic Mesh Dict<br />
<br />
- //g (0 9.8 0);<br />
<br />
// :: lOD :: angularMomentum (default = (0 10 0))<br />
<br />
<br />
2.<br />
<br />
Control Dict<br />
<br />
- Max Delta T : 0.01<br />
<br />
- End Time 10<br />
<br />
Dynamic Mesh Dict<br />
<br />
- //g (0 9.8 0);<br />
<br />
// :: lOD :: angularMomentum (default = (0 100 0))<br />
<br />
//- Angular momentum of the rigid-body in local reference frame<br />
<br />
angularMomentum (10 10 10);<br />
<br />
<br />
Hasil yang didapatkan adalah berdasarkan gambar sebagai berikut:<br />
<br />
1. Hasil simulasi 1<br />
<br />
[[File:VAWT Ales1.jpg|500px|center]]<br />
<br />
<br />
<br />
2. Hasil simulasi 2<br />
<br />
[[File:VAWT Ales2.jpg|500px|center]]<br />
<br />
<br />
== Economizer Hopper (CFDSof Simulation) ==<br />
<br />
Economizer Hopper merupakan alat untuk mengatasi permasalahan akibat ''fly ash'' yang berasal dari produk pembakaran batubara. Potensi yang mungkin terjadi adalah penumpukan ''fly ash'' pada economizer ''flue gas ducting'', ''blocking'' abu di elemen pre-air heater, serta pengikisan pada blade dan ''guide vane''. Dengan adanya modifikasi Hopper tersebut, abu atau ''fly ash'' yang dialirkan saat keluar dari Boiler akan tertampung pada bagian ''bottom ash'' tersebut. <br />
<br />
Pada kasus ini, dilakukan simulasi menggunakan CFDSof dengan melakukan pembeda antara economizer dengan hopper dan tidak. Analisa yang dilakukan adalah dengan simulasi secara ''transient'', kemudian dilakukan simulasi multifasa dengan pendekatan ''eulerian-langrangian'', dengan fasa padatan dalam bentuk ''fly ash'' serta liquid dalam bentuk gas yang mengalir pada sistem tersebut. <br />
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Hasil dari simulasi tersebut digambarkan melalui dokumentasi yang sudah dibagi berdasarkan beberapa tinjauan sebagai berikut:<br />
<br />
<br />
<br />
'''Analisa diameter partikel'''<br />
<br />
1. Tanpa Hopper<br />
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[[File:EconomizerTanpaHopper.gif|center|400px]]<br />
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[[File:Ales_ETH_Iso.gif|center|400px]]<br />
<br />
<br />
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2. Dengan Hopper<br />
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[[File:Ales_EH.gif|center|400px]]<br />
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[[File:Ales_EH_Iso.gif|center|400px]]<br />
<br />
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Melalui hasil ini, dapat disimpulkan bahwa dengan penggunaan hopper, mampu menangkap partikel ''fly ash'' pada wadah tertentu. Simulasi yang dilakukan dapat terlihat dari partikel berwarna merah yang mampu ditampung pada wadah tertentu saat melalui jalur tersebut. Partikel dengan ukuran yang lebih kecil, cenderung dapat melanjutkan sampai ke bagian outlet dari economizer hopper tersebut.<br />
<br />
<br />
----<br />
<br />
'''Analisa tekanan sistem'''<br />
<br />
<br />
[[File:Pressure_Econo_Ales.gif|center|400px]]<br />
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Pada hasil dari kedua simulasi tersebut, dapat terlihat bahwa tekanan pada bagian ''outflow'' semakin besar daripada bagian inlet dari sistem untuk kedua hasil uji coba. Hasil ini dikarenakan adanya perbedaan ketinggian yang terjadi sembari berjalannya ''fly ash'' kepada arah outflow tersebut. Tekanan ini diakibatkan karena adanya kecepatan di bagian inlet yang juga bisa mempengaruhi tekanan pada outlet tersebut. Tekanan ini terjadi pada sistem tersebut dan dapat mempengaruhi partikel yang bergerak melalui sistem tersebut. Pengaruh yang terjadi adalah kecepatan sistem tersebut untuk bergerak sepanjang sistem yang akan cenderung lebih cepat seiring dalam semakin besarnya tekanan pada sistem.<br />
<br />
----<br />
<br />
'''Analisa kecepatan sistem'''<br />
<br />
[[File:Velocity_Econo_Ales.gif|center|400px]]<br />
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Partikel tersebut akan bergerak terus menerus dan ada yang diakibatkan oleh kesetimbangan gaya (''bouyancy''), sehingga beberapa partikel bergerak dengan kecepatan yang berbeda. Partikel dengan massa yang lebih besar akan cenderung lebih dahulu, sedangkan yang tidak akan lebih mengalami gaya apung di dalam sistem tersebut. Dapat terlihat bahwa partikel dengan massa yang lebih berat (berdasarkan diameter) lebih dahulu menyentuh hopper (pada bagian dengan ada hopper) dan terjebak di dalam hopper tersebut. Sedangkan untuk yang lebih ringan, dengan kecepatan yang lebih pelan, akan cenderung mengapung dan masih ada kemungkinan bergerak ke bagian outlet dari sistem tersebut.<br />
<br />
== Validasi dan Verifikasi ==<br />
<br />
Validasi dan verifikasi menjadi salah satu langkah untuk melakukan simulasi CFD dengan secara kuantitatif mengestimasi error yang tetap serta ketidakpastian dalam simulasi numerikal. Walaupun keduanya memiliki definisi yang cukup dekat, kedua ini berdasarkan AIAA Guide (1998) menjadi dua hal yang sangat berbeda. <br />
<br />
'''Validasi''' : ''Solve the right equation'', berarti sebuah proses untuk memasukkan model simulasi yang tidak pasti dengan melakukan ''benchmarking'' dari data eksperimental. Apabila kondisi memenuhi, maka besaran dan tanda akan menyesuaikan error secara sendirinya dalam melakukan simulasi. Dalam prosedur ini dasarnya adalah melakukan pemastian hitungan dengan memberikan beberapa jangkauan kondisi fisik dari sistem yang didapatkan berasarkan perhitungan dan dibandingkan dengan hasil simulasi numerikal dalam beragam kondisi. Dari perbandingan terhadap kondsisi eksperimental ini, dapat terlihat seberapa jauh kesalahan yang terjadi.<br />
<br />
'''Verifikasi''' : ''Solve the equation right'', berarti sebuah proses untuk memasukkan simulasi numerikal yang tidak pasti dan apabila sesuai, memastikan besaran dan tanda dari error simulasi tersebut serta ketidakpastiannya. Pada bagian ini dasarnya adalah memastikan parameter yang digunakan pada saat dilakukan simulasi. Hal ini juga perlu diperhatikan besar mesh yang digunakan serta time-step yang terjadi, apakah sesuai atau tidak dalam dilakukan perhitungan tersebut.<br />
<br />
== Analisis CFD dalam Simulasi Cyclone Seperator ==<br />
<br />
'''Validasi'''<br />
<br />
[[File:GeomPaperAles.jpg|400px|center]]<br />
<br />
Pada kasus ini, dilakukan benchmarking berdasarkan paper ''Numerical Analysis of Gas-Solid Behavior in a Cyclone Separator for Circulating Fluidized Bed System'' (DOI:10.18869/acadpub.jafm.73.241.26951). Paper ini memberikan contoh ''property'' dari partikel solid berupa pasir dengan jangkauan diameter per partikel sekitar 100-425 µm dan kecepatan aliran pada bagian inlet sekitar 16 m/s. Alat ini pada dasarnya bekerja dengan memasukkan gas-solid pada bagian inlet dari sistem tersebut secara tangensial. Percepatan kemudian terbentuk secara ''helical'' karena bentuk dinding yang berupa ''cone''. Partikel yang lebih berat akan cenderung jatuh ke bawah, yaitu bagian outlet tersebut. Sedangkan, partikel yang lebih kecil lagi (seperti udara) akan mengalir mengarah bagian tengah dan mengarah ke ''vortex finder'' dari sistem tersebut. Hal ini akan membuat udara tersebut keluar pada bagian outlet di atas sistem.<br />
<br />
<br />
[[File:RSMTransportEqAles.jpg|400px|center]]<br />
<br />
Persamaan yang digunakan ini adalah ''transport equation'' untuk Reynolds stress model. Ruas kiri menunjukkan derivasi stress terhadap waktu dan ''convective transport'' pada sistem tersebut. Kemudian, ruas kanan menunjukkan beberapa variabel seperti ''stress diffusion'', ''shear production'', ''pressure-strain'', ''dissipation term'', dan Source ''S'' yang terjadi pada sistem tersebut. Berdasarkan paper ini, interaksi antar particle juga diabaikan untuk dilakukan analisa komputasi yang dilakukan. <br />
<br />
<br />
----<br />
'''Verifikasi'''<br />
<br />
Pada simulasi yang dilakukan, dilakukan dengan kondisi multiphase eulerian-langrangian untuk dilakukan simulasi ini. Kondisi tersebut kemudian dilanjutkan dengan distribusi partikel uniform dengan sekitar 4000 parcel per detiknya selama dua detik. Mesh pada geometri ini pada Δx, Δy, dan Δz, adalah masing-masing 18, 50, dan 21. Distribusi partikel (pasir) diasumsikan ''uniform'' (dengan alasan belum memahami perbedaannya), dengan range diameter seperti yang sudah dijelaskan pada bagian validasi serta kecepatan inlet (pada sumbu z pada geometri ini) dengan sebesar 16 m/s, sesuai dengan kecepatan inlet udara. Pada bagian geometri, inlet diasumsikan udara dengan 1.225 kg/m^3 dengan kecepatan 16 m/s. Bagian outlet atas dan bawah diasumsikan sebagai outflow sehingga udara dapat mengalir pada bagian tersebut. Simulasi yang dilakukan belum banyak dilakukan variasi karena sering terjadi ''error'' pada saat dilakukan simulasi. Setelah dilakukan diagnosa, kesalahan yang terjadi adalah adanya ''adjust time step'' yang dicentang sehingga mengalami ''error'' dan cenderung untuk mengalami software crash pada saat dilakukan. Berikut adalah bukti ''error'' yang terjadi pada saat dilakukan simulasi:<br />
<br />
<br />
[[File:CrashAles.jpg|400px|center]]<br />
<br />
[[File:ConvergeFailAles.jpg|300px|center]]<br />
<br />
<br />
<br />
Hasil ini menunjukkan bahwa sudah dilakukan percobaan dengan kondisi ''adjust time step'' sebagai berikut dengan iterasi tertentu. Kondisi ini menyebabkan adanya crash pada sistem tersebut sehingga tidak bisa dilakukan simulasi dengan kondisi ''adjust time step''. Akan tetapi, dilakukan simulasi kembali dengan kondisi ''boundary conditions'' yang sama namun dengan kondisi ''adjust time step'' yang tidak dilakukan variasi. Hal ini berhasil melakukan simulasi dengan baik, akan tetapi terjadi beberapa permasalahan yang terjadi juga pada kondisi ini.<br />
<br />
<br />
----<br />
<br />
'''Diameter Partikel'''<br />
<br />
[[File:CycDWTSAles.jpg|400px|left]]<br />
[[File:ParticleTraceAles.jpg|400px|right]]<br />
<br />
[[File:AlesResidual16.jpg|400px|thumb|center|Residual Perhitungan yang Masih Salah]]<br />
<br />
Gambar berikut menunjukkan hasil yang sudah ditunjukkan tanpa dengan melakukan ''adjust time step''. Terlihat walaupun cukup kecil bahwa adanya partikel (pasir) yang terjatuh ke bagian outflow bawah. Gas atau udara yang bersih seharusnya keluar pada bagian outflow atas, akan tetapi tidak dapat divisualisasikan melalui hasil simulasi yang sudah dilakukan. Time step yang tidak dilakukan penyesuaian pada simulasi tersebut menyebabkan adanya residual untuk ''turbulence'' menjadi sangat besar, sehingga masih banyak sekali kesalahan yang terjadi pada simulasi ini. Tinjauan ini setidaknya masih menunjukkan bahwa partikel tersebut dapat terpisahkan melalui bagian outflow di bawah, walaupun visualisasinya kurang begitu jelas dikarenakan diameter partikel yang relatif sangat kecil. <br />
<br />
<br />
'''Tekanan Sistem'''<br />
<br />
[[File:PressGraphY.jpg|400px|center]]<br />
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[[File:CycPressWTSAles.jpg|400px|center]]<br />
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Tekanan yang terjadi ini terlihat melalui visualisasi bahwa kecepatan inlet tersebut menyebabkan adanya tekanan yang besar pada bagian satu sisi dari dinding ''cyclone separator''. Hal ini karena kecepatan yang mendorong dinding tersebut ditambah lagi adanya partikel pasir yang terlibat pada fenomena tersebut. Berdasarkan grafik yang didapatkan juga, terlihat bahwa tekanan cenderung lebih besar pada bagian sisi atas dari sistem tersebut, daripada yang bagian bawah. Seharusnya ada variasi perbedaan terkanan yang terjadi akibat adanya inlet ini, namun dikarenakan simulasi yang begitu terbatas, tidak dapat terlihat secara jelas mengenai grafik tersebut. Bagian outflow atas dan bawah juga tervisualisasi bahwa adanya tekanan yang meningkat akibat adanya aliran tersebut. Perlu adanya beberapa koreksi seperti distribusi partikel yang terjadi pada sistem dan juga mesh yang perlu diperbaiki pada saat dilakukan simulasi.<br />
<br />
<br />
<br />
'''Evaluasi Pekerjaan'''<br />
<br />
Grafik lainnya tidak menunjukkan hasil yang jelas setelah dilakukan simulasi. Grafik partikel, kecepatan, turbulent, dan lain-lainnya tidak dapat divisualisasikan dengan jelas karena keterbatasan simulasi yang dilakukan. Perlu adanya perhatian yang lebih dalam terkait distribusi partikel tersebut serta visualisasi dari aliran udara, sehingga bisa ditunjukkan terpisahnya jalur udara bersih dan partikel pasir yang ada. Akan tetapi, grafik dan visualisasi yang ditunjukkan tersebut cukup menunjukkan mengenai fenomena multifasa yang terjadi pada sistem ''cyclone separator''. Oleh karena itu, dilakukan perbaikan terkait kesalahan yang terjadi tersebut menjadi lebih baik.<br />
<br />
<br />
'''Hasil Evaluasi'''<br />
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Pada simulasi ini, dilakukan pembeda yaitu pada kecepatan inlet dijadikan 5 m/s. Alasan ini masih belum diketahui penyebabnya, namun didapatkan bahwa grafik residunya sudah ''converge'' dan bisa dilakukan pada waktu sekitar 8 detik (sesuai dengan paper). Kondisi pada parcelnya dibedakan menjadi 2000 per second dengan lama waktu selama dua detik. Hal ini ditemukan adanya grafik kecepatan serta visualisasi pada sistem tersebut yang sudah benar. Tekanan sudah terdistribusi dengan baik serta terdapat visualisasi kecepatan yang keluar pada kedua outlet yang menunjukkan adanya udara mengarah ke atas. Grafik juga tersedia sebagai bukti adanya tekanan dan kecepatan yang menunjukkan hasil tersebut. Hasil yang didapatkan adalah sebagai berikut:<br />
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[[File:Residual1Ales.jpg|400px|thumb|center|Hasil Residual pada percobaan dengan v=5 m/s]]<br />
<br />
Pada hasil yang didapatkan, terlihat bahwa partikel yang digambarkan melalui vektor dengan warna bergerak dengan kecepatan yang bervariasi berdasarkan beratnya. Terlihat bahwa partikel tersebut berputar mengitari dinding cyclone dan mengarah ke bawah dalam beberapa detik. Dikarenakan hanya ditetapkan sekitar dua detik untuk masuk sebanyak 2000 parcels per second, maka setelah dua detik, tidak ada lagi partikel yang memasuki sistem tersebut. Setelah itu, terlihat bahwa gerakan partikel mengarah ke outlet di bagian bawah dan seketika tidak terlihat pada visualisasi tersebut. Dapat ditunjukkan bahwa adanya kecepatan inlet tersebut mendorong partikel untuk bergerak secara tangensial dan secara ''helical'' ke bagian outlet. Penggambaran terlihat sebagai berikut:<br />
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[[File:DvectorAles.gif|450px|thumb|center|Vektor Arah Partikel Berdasarkan Ukuran Diameter]]<br />
[[File:VelocityVAles.gif|450px|thumb|center|Vektor Kecepatan Partikel]]<br />
<br />
Distribusi tekanan dan kecepatan terlihat setelah adanya inlet yang masuk dengan besaran tertentu. Pertama melalui tekanan, terlihat bahwa adanya distribusi tekanan yang relatif besar pada bagian atas wall. Ini dikarenakan adanya tekanan dari inlet yang membuat tekanan terpusat di awal dinding tersebut. Kemudian, tekanan tersebut mulai tersebar dengan warna yang mulai berubah sepanjang wall dari ''cyclone'' tersebut. Disini terlihat bahwa persebaran tekanan sebenarnya bergerak juga secara helikal, namun tidak merata sama besarnya karena adanya kecepatan yang cenderung berubah relatif lebih lambat. Kemudian, distribusi kecepatan terlihat bahwa adanya partikel yang awal mulanya mengenai dinding dari inlet tersebut, kemudian tervisualisasi secara gradasi bahwa kecepatan mulai melambat setelah melewati inlet tersebut. Partikel yang jatuh ke bawah terlihat bahwa outlet tersebut menunjukkan adanya partikel yang terjatuh pada bagian itu. Dinding juga ada yang berubah warna menjadi lebih hijau (menandakan kenaikan kecepatan) serta adanya kenaikan kecepatan pada outlet bagian atas. Ini juga menunjukkan bahwa adanya udara yang juga mengarah keatas akibat vortex finder dari sistem. Visualisasi dari simulasi tersebut terlihat di bawah berikut:<br />
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[[File:PressureDisAles.gif|400px|thumb|center|Distribusi Tekanan]]<br />
[[File:VelocityDisAles.gif|400px|thumb|center|Distribusi Kecepatan]]<br />
<br />
<br />
Lalu dari hasil grafik, dapat terlihat juga bahwa pada sumbu Z (horizontal pada dinding), tekanan pada bagian tengah cenderung mengecil dan besar pada bagian dekat dinding. Dapat terlihat bahwa tekanan tersebut besar karena adanya partikel yang berputar mengarah ke dinding tersebut. Pada sumbu Y (vertikal terhadap dinding), cenderung membesar pada bagian bawah dan atas juga cukup besar, akan tetapi mengecil juga pada sepanjang titik tengah dari dinding ''cyclone'' tersebut. Kecepatan pada sumbu Z juga terlihat cukup besar (secara magnitude). Dapat ditunjukkan juga bahwa bagian tengah tersebut relatif besar (pada sumbu Z) karena tidak adanya gesekan terhadap dinding sehingga relatif untuk mengalami gerak jatuh bebas. Berbeda dengan yang di dekat dinding, adanya gesekan membuat kecepatan menjadi relatif kecil. Secara sumbu Y, terlihat bahwa adanya kecepatan dengan besaran yang selalu ada. Besarannya berbeda-beda, pengaruh juga dari tekanan yang juga berbeda-beda. Besaran ini mungkin belum tentu akurat (karena adanya faktor error atau mesh), akan tetapi sudah cukup menunjukkan adanya fenomena yang kurang lebih benar terjadi pada sistem ''cyclone separator'' tersebut. Berikut adalah grafik mengenai hasil pada sumbu Z dan Y:<br />
<br />
<br />
[[File:GraphZ1.jpg|300px|thumb|center|Grafik pada Sumbu Y (Inlet 5 m/s)]]<br />
[[File:GraphY1Ales.jpg|300px|thumb|center|Grafik pada Sumbu Y (Inlet 5 m/s)]]<br />
<br />
== Volume of Fluid (VoF) ==<br />
<br />
== Sinopsis Tugas Besar Aplikasi CFD ==<br />
<br />
<br />
'''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''<br />
<br />
The gas-liquid separator has been widely used in the oil and gas industry to improve product quality. To design and operate the system at a low cost, mathematical modeling becomes very useful. The separator apparatus has three geometrical designs, such as horizontal, vertical, and spherical types, with the horizontal design with the lowest expense in production processes. The horizontal design has three main processes: the separation process, the liquid outlet process, and the gas outlet process. First, the separation process involves a diverter that reduces the gas-liquid velocity and diverts downwards into the separator affected by gravity. Then, the liquid droplets that are larger than a certain size will fall into the separator and continue their flow with a certain amount of liquid at the bottom of the separator to the system's outlet. Finally, the rest of the droplets with a smaller amount of size are considered a gas, which will continue its flow into the upper outlet. The study will use Computational Fluid Dynamics with Multiphase Eulerian-Langrangian method. There will be a variation between a diverter and the flow inlet distance, measured upon its efficiency in separating the gas and the fluid.<br />
<br />
== [[TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator''']] ==<br />
<br />
== Referensi Pembelajaran ==<br />
<br />
<br />
[1] Versteeg, H.K. and Malalasekera, W., 2007. An introduction to computational fluid dynamics: the finite volume method. Pearson education.<br />
<br />
[2] Tu, J., Yeoh, G.H. and Liu, C., 2018. Computational fluid dynamics: a practical approach. Butterworth-Heinemann.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52626TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:52:54Z<p>Alesdaniel: /* Abstract */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSOF® Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
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== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
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3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
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The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52625TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:52:07Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure 11.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph 6.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52624TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:51:47Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure 11.''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Graph 6.''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52623TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:51:16Z<p>Alesdaniel: /* Separator Distance Variations */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 7 until 10 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 7.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 2.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Graph 3.''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Graph 4.''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Graph 5.''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52622TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:50:05Z<p>Alesdaniel: /* Validation */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Graph 1.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52621TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:49:42Z<p>Alesdaniel: /* Separator Distance Variations */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure 7.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52620TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:49:29Z<p>Alesdaniel: /* Separator Distance Variations */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure 7.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure 8 until 12 depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure 8.''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure 9.''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure 10.''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure 12.''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Graph 1.''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52619TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:48:49Z<p>Alesdaniel: /* Validation */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure 7.''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52618TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:48:38Z<p>Alesdaniel: /* Boundary Conditions and Solver Control */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 6.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52617TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:47:52Z<p>Alesdaniel: /* Abstract */</p>
<hr />
<div>== Abstract ==<br />
<br />
Horizontal Separators are a useful part of the petroleum industry. Many petroleum industries are still using the system due to the low maintenance price than the others. A striking, remarkable feature of the system, which is the separator or diverter, could separate multiple phases in the crude oil into a single oil phase based on the American International Petroleum Standard. However, there is no clear standard that defines the size and location of the apparatus. In this study, the separator is performed in a numerical simulation using empirical correlations from literature and CFDSof Software. Each of the separators is in a determined location and conditions with expectations of viable advantages from the simulations. This study's findings bring strong evidence that a certain condition of separators, such as distances and perforated conditions, satisfies the effectiveness in providing separated crude oil. <br />
<br />
'''Keywords''': Horizontal Separator, Numerical Simulation, Two-phase, Distance, Perforated, Efficiency<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52616TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:29:43Z<p>Alesdaniel: /* Acknowledgement */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. I gratefully acknowledge the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. I also thank M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52615TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:29:12Z<p>Alesdaniel: /* Acknowledgement */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This work was carried out as a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The author gratefully acknowledges the help provided by Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor. The author also thanks M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52613TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:27:27Z<p>Alesdaniel: /* Conclusions */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
In summary, the work of two-phase numerical simulation in horizontal flow gas-liquid separator could gain a beneficial impact in processing crude oil. Although some evidence from the simulation implies that the current effectiveness is lower than the previous study, it still provides acceptable results. The separator will suffice the separation if the distance is large enough to achieve a greater outlet flow rate. The additional perforated separator also increases the effectiveness of the system in separating the oil and the gas. The work clearly has some limitations. Nevertheless, this work could be a framework for future numerical simulation. It is recommended that further research should be undertaken with accurate meshing and actual data of both phases. This numerical simulation and development in horizontal separators will be a challenge for us for next years.<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52610TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:18:00Z<p>Alesdaniel: /* Separator Distance Variations */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. The evidence from this study implies that a much farther distance of the separator would increase the system's efficiency.<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52608TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:16:10Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. <br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet. The result of this study suggests that an additional perforated separator increases the flow rate of the oil droplets that travel inside the system.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52602TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:14:24Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. <br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity (Graph _.), but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude of 12 mm in Diameter Perforated Separator]]<br />
[[File:GraphPerf1.png|400px|thumb|center|'''Figure .''' Graph Result of 12 mm in Diameter Perforated Separator]]<br />
<br />
The other perforated separator, which is 25 mm in diameter, should be analyzed regarding the results. The current 12 mm in diameter perforated separator should also be analyzed using the previous section simulation with 30x30x30 division to achieve a successful mesh generation. However, there was a problem that unable to perform such kind of simulation. The meshed separator was generated in unperforated conditions for the 12 mm in diameter and the other disappears after the mesh has been generated. Although such limitations occurred during the simulation and not able to obtain the same result from the previous studies, it was still acceptable from the current result that it satisfies the calculation.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:GraphPerf1.png&diff=52592File:GraphPerf1.png2021-01-05T12:07:37Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52590TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:07:08Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. <br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity, but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet.<br />
<br />
[[File:Perf1VelMag.png|550px|thumb|center|'''Figure .''' Velocity Magnitude with 12 mm Diameter Perforated Separator]]<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52589TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T12:06:58Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. <br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity, but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet.<br />
<br />
[[File:Perf1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 12 mm Diameter Perforated Separator]]<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:Perf1VelMag.png&diff=52582File:Perf1VelMag.png2021-01-05T11:56:32Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52580TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T11:53:48Z<p>Alesdaniel: /* Results and Discussions */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 10 seconds time control with 0.01 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 10 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-4</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:ResidualOverall2.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. <br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity, but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:ResidualOverall2.jpg&diff=52578File:ResidualOverall2.jpg2021-01-05T11:53:10Z<p>Alesdaniel: </p>
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<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:Residual_Overall.jpg&diff=52573File:Residual Overall.jpg2021-01-05T11:51:42Z<p>Alesdaniel: Alesdaniel uploaded a new version of File:Residual Overall.jpg</p>
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<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52570TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T11:50:46Z<p>Alesdaniel: /* Separator Distance Variations */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 25 seconds time control with 0.05 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 25 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-3</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:Residual Overall.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. <br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
[[File:GraphSepN1Y.png|400px|thumb|center|'''Figure .''' Result Graph with 100 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN2Y.png|400px|thumb|center|'''Figure .''' Result Graph with 120 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN3Y.png|400px|thumb|center|'''Figure .''' Result Graph with 140 mm Separator Distance From Inlet ]]<br />
[[File:GraphSepN4Y.png|400px|thumb|center|'''Figure .''' Result Graph with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity, but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:GraphSepN4Y.png&diff=52569File:GraphSepN4Y.png2021-01-05T11:49:35Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:GraphSepN3Y.png&diff=52568File:GraphSepN3Y.png2021-01-05T11:49:21Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:GraphSepN2Y.png&diff=52566File:GraphSepN2Y.png2021-01-05T11:49:09Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:GraphSepN1Y.png&diff=52565File:GraphSepN1Y.png2021-01-05T11:49:01Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52564TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T11:48:37Z<p>Alesdaniel: /* Separator Distance Variations */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 25 seconds time control with 0.05 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 25 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-3</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:Residual Overall.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which was also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve the system's efficiency due to the velocity outlet that is greater than the inlet. Another alternative was then found by using lower mesh divisions because the higher mesh indicated a piece of information that stated ''Failed 1 mesh checks''. It was then finally managed through another investigation and resulted in significant differences.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
An alternative version was done to prove the previous study. It also managed to calculate the system's efficiency, although the calculation was not performed through mass flow rate. The mass flow rate calculation was unable to be performed due to the limitations in ParaView software. The efficiency was obtained through the surface integral of the outlet's area to the inlet's area. It was then calculated based on the flow rate that occurs in the system. This is slightly different from the previous attempt through mass flow rate calculation. Despite the different methods, the current calculation is acceptable regarding the velocity should meet the indication of the flow that travels in the system. Based on the result, the more distance between the inlet and the separator should increase the number of efficiencies, which in this case, the 180 mm distance reaches 60.3%. This is slightly different from the previous attempt by Bayraktar, et al. (2017) and Efendioglu et al. (2014), which shows a large percentage of efficiency around more than 90%. Despite that, this simulation succeeds in fulfilling the requirement in achieving the systems that should have done. <br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Horizontal Separator Efficiency<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Distance from Inlet Velocity (m)<br />
|-<br />
! scope="row" | 100 mm<br />
| 53.1% <br />
|-<br />
! scope="row" | 120 mm<br />
| 51.5%<br />
|-<br />
! scope="row" | 140 mm<br />
| 54.5% <br />
|-<br />
! scope="row" | 180 mm<br />
| 60.3% <br />
|}<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity, but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:SepN4VelMag.png&diff=52553File:SepN4VelMag.png2021-01-05T11:27:51Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:SepN3VelMag.png&diff=52552File:SepN3VelMag.png2021-01-05T11:27:44Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:SepN1VelMag.png&diff=52551File:SepN1VelMag.png2021-01-05T11:27:35Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52543TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T11:20:16Z<p>Alesdaniel: /* Separator Distance Variations */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 25 seconds time control with 0.05 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 25 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-3</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:Residual Overall.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation, by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve an efficiency of the system due to the velocity outlet that is greater than the inlet. Further investigation of the mass flow rate in the system needs to be considered carefully to achieve efficiency.<br />
<br />
[[File:SepN1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:SepN2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:SepN3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:SepN4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity, but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=File:SepN2VelMag.png&diff=52542File:SepN2VelMag.png2021-01-05T11:20:13Z<p>Alesdaniel: </p>
<hr />
<div></div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52540TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T11:15:19Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 25 seconds time control with 0.05 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 25 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-3</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:Residual Overall.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation, by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve an efficiency of the system due to the velocity outlet that is greater than the inlet. Further investigation of the mass flow rate in the system needs to be considered carefully to achieve efficiency.<br />
<br />
[[File:Sep1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:Sep2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:Sep3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:Sep4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). Based on the visualization by ParaView software, it shows that the flow penetrates through the hole of the perforated separator. This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity, but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet. In the actual previous study, the perforated separator should have increased the system's efficiency due to the filtered oil droplets that occurred. Although the current result slightly misses proofing the past evidence, it still shows that the separator increases the system's efficiency in delivering oil droplets into the system's outlet.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52539TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T11:10:50Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 25 seconds time control with 0.05 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 25 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-3</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:Residual Overall.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation, by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve an efficiency of the system due to the velocity outlet that is greater than the inlet. Further investigation of the mass flow rate in the system needs to be considered carefully to achieve efficiency.<br />
<br />
[[File:Sep1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:Sep2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:Sep3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:Sep4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (2000). These simulations then compared with the previous result with the one unperforated separator. This comparison is fixed in one distance between the inlet and the separator, at 100 mm. Based on the visualized velocity magnitude, the perforated result achieved a greater velocity than the previous one (Figure _.). This then embarked on the perforated separator's advantage in providing a sufficient mass flow rate. However, this result still brought a discrepancy in the expected result. It achieved a greater outlet velocity, but still far as expectation regarding the flow separated by the separator should have been lowered when travels into the system's outlet.<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdanielhttp://air.eng.ui.ac.id/index.php?title=TUGAS_BESAR_APLIKASI_CFD:_%27%27%27Two-Phase_Simulation_in_Horizontal_Flow_Gas-Liquid_Separator%27%27%27&diff=52538TUGAS BESAR APLIKASI CFD: '''Two-Phase Simulation in Horizontal Flow Gas-Liquid Separator'''2021-01-05T11:03:07Z<p>Alesdaniel: /* Perforated Separator */</p>
<hr />
<div>== Abstract ==<br />
<br />
== Introduction ==<br />
<br />
Petroleum reaches the surface as a mixture consisting of gas and fluid substance. To achieve an adequate quality of petroleum, one needs to satisfy a petroleum refinery process, which requires deliberation in multiphase separation. A gas-liquid separator was designed to separate two different substances using a diverter inside the system. To acquire efficient separation, one needs to consider the effective diverter near the system's inlet. This consideration requires a perilous investigation, which numerical modeling would be utilized in achieving the low cost and minimum risk investigation upon the system. In petroleum production, there are several types of separators. The separators are used based on the numbers of phases, crude oil properties, and separator conditions. These are vertical, horizontal, and spherical separators, which are widely used in production. Regarding the lowes cost expense in these separators, the horizontal separator has the lowest ones. This separator is considered as a gravity-based facility that was designed to provide sufficient time for droplets separation. The schematic flow direction of this system will be depicted below to ensure the simplicity of the system.<br />
<br />
[[File:HorizontalSeparatorAles.jpg|500px|thumb|center|'''Figure 1.''' Horizontal Separator Inner Geometry and Flow Direction]]<br />
<br />
== Objectives ==<br />
<br />
In this simulation, there will be various assumptions due to the model limitations. First of all, the model that will be simulated applies for a two-phase separator only. The real case in using the system would be in a three-phase consideration. Second, there would be numerous neglections since the simulation only focuses on the two-phase separation. There would be no other additional phase separators, such as coalescer, vortex breaker, or baffle, widely used in the actual system. The simulation will only focus on the inlet velocity and separator distance variation to acquire its effectiveness. For further objectives will be mentioned below:<br />
<br />
1. To evaluate the system's effectiveness by comparing the previous simulation with the redesigned 3D simulation.<br />
<br />
2. To investigate the most efficient separator within several distances from the inlet and various inlet velocities.<br />
<br />
3. To investigate the suitable separator with and without a perforated separator.<br />
<br />
== Numerical Geometry ==<br />
<br />
The geometry would be the same as the previous study by Efendioglu, et al. (2014), and the regulations on oil handling systems. For simplicity in simulation, the geometry would be in two-dimension, and the result's validation will be performed to achieve the similarities from the 3D simulation. The additional internal apparatuses would be neglected and only using the diverter considered in the simulation. This would point out each of the phase separations as perceptible as the post-processor can with acceptable information to a certain condition. In this simulation, the diverter's distance bears a close resemblance to the one proposed by Bayraktar, et al. (2017), with customization of limiting the diverter distance up to 180 mm from the inlet. The distances are an interval of 20 mm from 100 mm until 140 mm, and an additional 180 mm distance. It was decided that the best method for this study was to evaluate the actual approach in obtaining the flow rate at the system's outlet.<br />
<br />
[[File:HorSep3D.jpg|450px|thumb|center|'''Figure 2.''' Horizontal Separator 3D Geometry]]<br />
<br />
The diverter would then be modified into a perforated baffle applied in an actual horizontal separator. In this case, the procedure used is as proposed by Efendioglu et al. (2014) and Wilkinson et al. (2000) [5]. The perforated baffle diameter is 12 mm and 25 mm (Figure 4. and Figure 5.), and each of them is compared with the unperforated baffle (Figure 3.). This then will also be compared between the flow rate at the system's outlet. The scope of this study is to obtain evidence that using a perforated separator would increase the efficiency in delivering the oil into the outlet.<br />
<br />
<br />
[[File:Sep.png|400px|thumb|center|'''Figure 3.''' Unperforated Baffle or Separator]]<br />
[[File:Sep12.png|400px|thumb|center|'''Figure 4.''' Perforated Baffle or Separator with 12 mm Diameter]]<br />
[[File:Sep25.png|400px|thumb|center|'''Figure 5.''' Perforated Baffle or Separator with 25 mm Diameter]]<br />
<br />
== Methodology ==<br />
<br />
=== Software ===<br />
The numerical simulation will be using CFDSOF® (for the pre-processing and the processing step), the first Indonesian CFD software established by PT CCIT Group Indonesia, and ParaView as the post-processor of the simulation.<br />
<br />
=== Mathematical Model (Verification) ===<br />
<br />
The simulation was solved using the Large Eddy Simulation (LES), k-ε turbulence model. In order to ease the visualization between phases, the multiphase Eulerian-Langrangian model is being implemented, which attributes separate momentum and continuity equations for each phase. The flow is assumed to be incompressible, which then the governing equation in this simulation can be written as below:<br />
<br />
[[File:GovEq.jpg|500px|thumb|center]]<br />
<br />
These equations represent the simulation between the phases, which in this case is between oil droplets and gas. Because the flow incompressibility occurs during the numerical simulation, the energy equation is neglected. The turbulence equation for the gas phase has been widely addressed by previous researchers using the Reynolds stress equation[6]. It can be written as: <br />
<br />
[[File:TurbulenceUAS.jpg|500px|thumb|center]]<br />
<br />
Cij represents the rate of convection, Pij is the production rate, Dij is the transport by diffusion, ϵij is the rate of dissipation, Πij is the transport due to turbulent pressure strain interactions Ωij is the transport due to rotation.<br />
<br />
In this study, the oil is considered as droplets with a certain diameter. In this case, the droplets are assumed to be 10 μm. The drag that occurred upon droplets is presumably in the sphere-drag model, injected through the system's inlet. In this simulation, there is no evidence regarding the parcel numbers that occur in the system from the previous studies. However, the simulation setup bears a close resemblance to the same as the one proposed by Efendioglu, et al. [6] and Yayla, et al. [1]. The simulation is assumed to use the mass flow rate from both pieces of literature in order to reach the similarity in numerical simulation. Such an unjustified assumption can lead to grave consequences with regard to the result of the simulation. It is satisfied by the [[two-dimensional numerical simulation]] result.<br />
<br />
=== Grid Independent Study ===<br />
<br />
A grid independent study was performed to achieve minimum error in the simulation. The geometry without separator was used in this study to achieve the result. Mesh changes in each of the coordinates were compared with the velocity at the outlet. The study was started from the coarse grid until the fine grid to point out some differences. However, this study has a limitation when applying the solved geometry in the Paraview post-processor. A satisfactory justification regarding the mesh is varying the mesh in low numbers. This achieves an acceptable result by comparing velocities in each of the simulation outlets. In this grid independent study, the mesh that has been used for further simulations are 75x75x60 divisions. A division that exceeds the current division resulted in an error in post-processing visualization. The data that has been measured is explained in detail division measures below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Grid Independent Study<br />
|-<br />
! scope="col" | Mesh Division !! scope="col" | Velocity (m/s)<br />
|-<br />
! scope="row" | 10 x 10 x 10<br />
| 2,04 <br />
|-<br />
! scope="row" | 30 x 30 x 30<br />
| 2,7<br />
|-<br />
! scope="row" | 45 x 45 x 45<br />
| 4,08 <br />
|-<br />
! scope="row" | 60 x 60 x 60<br />
| 4,8 <br />
|-<br />
! scope="row" | 75 x 75 x 60<br />
| 5,32<br />
|}<br />
<br />
=== Boundary Conditions and Solver Control ===<br />
<br />
The boundary conditions are assumed to be one inlet and two outlets. Both of the outlets use a different amount of pressure due to the height effect. The bottom outlet is 14.58 Pa, and the upper outlet is 0 Pa. This assumption is based on the basic hydrostatic pressure formula. Although the previous studies have shown that the inlet flow was set to be a certain mass flow rate, this simulation uses a certain amount of velocity regarding the software's limitations. In this simulation, the velocity inlet was assumed to be 5 m/s for both oil droplets and airflow through the inlet. Given that these findings are based on a limited flow rate available from the software, the results from such analyses should thus be treated with many assumptions. The height uses the bottom outlet as the datum, and gas density is used. The fluid properties on both phases and boundary conditions are written specifically in the table below:<br />
<br />
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"<br />
|+ style="text-align: center;" | Fluid Properties<br />
|-<br />
! scope="col" | Fluid Type !! scope="col" | Density (kg/m<sup>3</sup>) !! scope="col" | Dynamic Viscosity (Pa.s) !! scope="col" | Mass Flow Rate (kg/s)<br />
|-<br />
! scope="row" | Oil<br />
| 824.95 || 0.00237 || 0.5<br />
|-<br />
! scope="row" | Gas<br />
| 1.225 || 1.79E-5 || 0.5<br />
|}<br />
<br />
[[File:Bcond.jpg|500px|thumb|center|'''Figure 3.''' Boundary Conditions of the Horizontal Separator System]]<br />
<br />
== Results and Discussions ==<br />
<br />
=== Validation ===<br />
<br />
The simulation was first investigated under [[two-dimensional numerical simulation]], using the same geometry. The two-dimensional simulation opted for simplification regarding the simulation. A single-phase simulation was examined in the simulation to achieve a simplification of the validity of the results. This was done utilizing CFDSof software with Paraview as the post-processor. However, it was found that the simulation does not satisfy the governing equation. These findings are in contradiction to previous results reported in the literature. It somehow differs from the basic equation of hydrostatic pressure in visualizing the system's pressure and velocity. The study was unsuccessful in proving that two-dimensional numerical simulation would satisfy a justification for the three-dimensional approach. Despite the unsatisfactory results, the next simulation is using a three-dimensional and multiphase approach. The simulation is still restricted only using two-phase, which are gas and oil droplets. It is plausible that a number of limitations could have influenced the results obtained.<br />
<br />
The simulation was done in transient-state with the LES Turbulence model. It was solved in 25 seconds time control with 0.05 seconds time step. The expected residual in this simulation was 10<sup>-6</sup> for every iteration performed. Unfortunately, the results did not achieve the targeted amount after 25 seconds of iteration. This could lead to insufficiency in terms of providing accurate data and visualization. However, the residual was acceptable although it did not meet the required amount. It reached under 10<sup>-3</sup>, which in this case is acceptable. The graph for every simulation was similar to another, and below is one of the residual graphs:<br />
<br />
[[File:Residual Overall.jpg|600px|thumb|center|'''Figure .''' Simulation Residual Result ]]<br />
<br />
=== Results ===<br />
<br />
==== Separator Distance Variations ====<br />
<br />
Surprisingly, with an assumed value of velocity inlet around 5 m/s, magnitudes of the system were found in different separator distances. As might have been expected, every result was not successful in proving similarities with the previous research. It was found that using the variety of separator distances and the magnitude did not indicate oil droplets and gas migration into the system's outlet (Figure). Despite the lack of visualization, the findings are compared with the previous results regarding the system's outlet in various separator distances. Figure _ until _ depicts that the system's velocity outlet in the Y-axis increases in separator distance increment. These results have shown a similarity between the present study with the previous study by Bayraktar, et al. (2017) and Efendioglu et al. (2014). Although the performance was not ideal, this simulation is still believed that there is a satisfactory agreement in both the system's outlets.<br />
<br />
Regarding the system's efficiency, there were some discrepancies due to the software's limitation in boundary conditions, as expected beforehand. The efficiency is calculated from the bottom outlet's mass flow rate to the inlet's mass flow rate. The mass flow rate for the system's inlet was assumed to be 0.5 kg/s, according to the previous study by Bayraktar, et al. (2017). In this case, due to the software's limitation, oil droplets were assumed to be in a discrete phase, which also considered as a particle. This led to a discrepancy in achieving the viscous effect that occurs during the simulation. A manual investigation, by integrating the surface vector using the ''integrate variable'' feature in the ParaView software was also done to find the flow rate. It still did not fulfill the requirement to achieve an efficiency of the system due to the velocity outlet that is greater than the inlet. Further investigation of the mass flow rate in the system needs to be considered carefully to achieve efficiency.<br />
<br />
[[File:Sep1VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 100 mm Separator Distance From Inlet ]]<br />
[[File:Sep2VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 120 mm Separator Distance From Inlet ]]<br />
[[File:Sep3VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 140 mm Separator Distance From Inlet ]]<br />
[[File:Sep4VelMag.png|400px|thumb|center|'''Figure .''' Velocity Magnitude with 180 mm Separator Distance From Inlet ]]<br />
<br />
==== Perforated Separator ====<br />
<br />
In this section, the same simulation was performed as the previous one. The differences here were perforated separators by previous studies from Wilkinson et al. (<br />
<br />
== Conclusions ==<br />
<br />
== Acknowledgement ==<br />
<br />
This paper is a final assignment in the Computational Fluid Dynamics course at the Department of Mechanical Engineering, University of Indonesia. The highest gratitude for Dr. Ir. Ahmad Indra Siswantara, as this paper's advisor, and also M Hilman Gumilar Syafei, Abdullah Robanni, Bintang Farhan, Abi Rizky, Elvin, Agus P Nuryadi, Josiah Enrico, and the rest of my colleagues who took this course.<br />
<br />
== References ==<br />
<br />
[1] Yayla, Sedat & Kamal, Karwan & Bayraktar, Seyfettin & Oruç, Mehmet. (2017). TWO PHASE FLOW SEPARATION IN A HORIZONTAL SEPARATOR BY INLET DIVERTER PLATE IN OILFIELD INDUSTRIES.<br />
<br />
[2] Eissa, M., 2013. Influence of Flow Characteristics on the Design of Two-Phase Horizontal Separators. Journal of Engineering and Computer Science (JECS), 15(2), pp.50-62.<br />
<br />
[3] Adeniyi, O., 2004. Development of Model and Simulation of a Two-Phase, Gas-Liquid Horizontal Separator. Leonardo Journal of Sciences, 3(5), pp.34-45.<br />
<br />
[4] Kharoua, N., Khezzar, L. and Saadawi, H., 2013. CFD modelling of a horizontal three-phase separator: a population balance approach. American Journal of Fluid Dynamics, 3(4), pp.101-118.<br />
<br />
[5] Wilkinson, D., Waldie, B., Nor, M.M. and Lee, H.Y., 2000. Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering Journal, 77(3), pp.221-226.<br />
<br />
[6] Efendioglu, A., Mendez, J. and Turkoglu, H., 2014. The numerical analysis of the flow and separation efficiency of a two-phase horizontal oil-gas separator with an inlet diverter and perforated plates. Advances in Fluid Mechanics, 10, p.133.<br />
<br />
[7] Stewart, M. and Arnold, K.E., 2011. Surface production operations, Volume 1: Design of oil handling systems and facilities (Vol. 1). Elsevier.</div>Alesdaniel