Flow Boiling

Ramin.Mashayekhi · March 7, 2016, 05:08

Hello guys
I am new at CFX
I am going to simulate flow boiling in a channel and I have lots of questions.
1) is there any other models for simulating boiling? (i just know RPI)
2) Can I use RPI for horizontal channel ?
3) Is it possible use RPI for rectangular channel or it just for tubes?
4) CFX or Fluent , which one is better for simulating Boiling?
Thanks in Advance

Amar Kad · March 12, 2016, 14:16

Hi Ramin
Both fluent and cfx have the ability to simulate flow boiling but i prefer fluent for flow boiling while CFX uses for turbomachinery simulation
i have the same problem now and i use CFX for solving boiling of flow
if you have any advise for me say it for me
thanks

rampal · November 21, 2017, 00:53

Hi Friends, I'm doing horizontal flow boiling simulation in fluent, but not getting converged solution. Initially the residuals are going down well but the simulation got diverged after some iterations. I'm using eulerian wall boiling model for this problem. Have anyone done this type of problem ? I need your valuable help to solve this problem.

I have successfully done this for vertical pipe flow.

JuPa · November 24, 2017, 08:44

Don't use the segregated solver. Couple the volume fraction inside the same matrix as velocity and pressure. This improves convergence by a lot. At the same time you need to use a physical time scale representative of your bubble departure frequency. I.e. very small time steps (order 1E-4).

I got even better convergence by introducing a false source term and adding a large linearization coefficient.

ghorrocks · November 25, 2017, 06:38

I think Ram is talking about Fluent and I don't think all those options are available in Fluent.

Ram: If your post is about fluent then please post on the fluent forum.

JuPa · November 27, 2017, 10:03

I think you can still do those things in Fluent. But Fluent being Fluent it'll be 1000% more difficult to implement compared to CFX. Might also include some absurd UDF and a billion hours of trial and error tinkering with under relaxation factors.

March 7, 2016, 05:08	Flow Boiling	#1
Ramin.Mashayekhi New Member Ramin Join Date: Jan 2016 Location: Iran Posts: 1 Rep Power: 0	Hello guys I am new at CFX I am going to simulate flow boiling in a channel and I have lots of questions. 1) is there any other models for simulating boiling? (i just know RPI) 2) Can I use RPI for horizontal channel ? 3) Is it possible use RPI for rectangular channel or it just for tubes? 4) CFX or Fluent , which one is better for simulating Boiling? Thanks in Advance

November 21, 2017, 00:53	Horizontal flow boiling	#3
rampal Member Ram Kumar Pal Join Date: Apr 2015 Posts: 38 Rep Power: 11	Hi Friends, I'm doing horizontal flow boiling simulation in fluent, but not getting converged solution. Initially the residuals are going down well but the simulation got diverged after some iterations. I'm using eulerian wall boiling model for this problem. Have anyone done this type of problem ? I need your valuable help to solve this problem. I have successfully done this for vertical pipe flow.

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March 12, 2016, 14:16		#2
Amar Kad Member Amar Join Date: Jan 2016 Posts: 39 Rep Power: 10	Hi Ramin Both fluent and cfx have the ability to simulate flow boiling but i prefer fluent for flow boiling while CFX uses for turbomachinery simulation i have the same problem now and i use CFX for solving boiling of flow if you have any advise for me say it for me thanks

November 24, 2017, 08:44		#4
JuPa Senior Member Mr CFD Join Date: Jun 2012 Location: Britain Posts: 361 Rep Power: 15	Don't use the segregated solver. Couple the volume fraction inside the same matrix as velocity and pressure. This improves convergence by a lot. At the same time you need to use a physical time scale representative of your bubble departure frequency. I.e. very small time steps (order 1E-4). I got even better convergence by introducing a false source term and adding a large linearization coefficient.

November 25, 2017, 06:38		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	I think Ram is talking about Fluent and I don't think all those options are available in Fluent. Ram: If your post is about fluent then please post on the fluent forum.

November 27, 2017, 10:03		#6
JuPa Senior Member Mr CFD Join Date: Jun 2012 Location: Britain Posts: 361 Rep Power: 15	I think you can still do those things in Fluent. But Fluent being Fluent it'll be 1000% more difficult to implement compared to CFX. Might also include some absurd UDF and a billion hours of trial and error tinkering with under relaxation factors.