How to estimate mass evaporated in 2-phase?

mariam.sara · January 4, 2013, 10:37

Hi I am tried to compute heat and mass transport from saturated vapour to liquid over a free surface in which both phases flowing into square duct (1 m x 1 m ) as a separated layers (stratified flow) with different velocities and there is heat flux at the lower wall as illustrated in pict may somebody tell me steps of modeling like this problem in CFX and which model should be used?

ghorrocks · January 5, 2013, 05:22

Develop each physics model separately - do a free surface model by itself, do a phase change model by itself before combining them together. If the sub-models are not working you have no hope for the full model.

Do all the CFX tutorials about multiphase, and read the documentation for multiphase. It is far better if you select the models you end up using because then you know what is going on. If you do not know what is going on then you have no hope of getting this to run.

mariam.sara · January 5, 2013, 06:33

Thanks a lot ghorrocks for the valuable answer I will try follow your recommendations. Currently I only read the tutorial that related to free surface model. I have few questions about your reply hope you illustrate its to me:
1) You said i need first to use the free surface model, which one you mean the homogeneous or in-homogeneous model?
2) With selecting phase change model did you mean I run the problem as single phase flow? if not how i can combine between free surface model and phase change model?

Thanks
mariam

ghorrocks · January 6, 2013, 05:42

1) I really think you should answer this question yourself. This is a fundamental decision in terms of the basic approach you are using so if you do not know the answer to this question then you are not ready to proceed anyway. Do further reading and tutorials and you will work it out for yourself.
2) Phase change modelling is inherently a multiphase simulation - so it cannot be run single phase. Just whatever approach you do make sure you start simple, get it working properly, then build on it to make more complex models. If you jump straight into a complex model you will never get it working.

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January 5, 2013, 05:22		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Develop each physics model separately - do a free surface model by itself, do a phase change model by itself before combining them together. If the sub-models are not working you have no hope for the full model. Do all the CFX tutorials about multiphase, and read the documentation for multiphase. It is far better if you select the models you end up using because then you know what is going on. If you do not know what is going on then you have no hope of getting this to run.

January 5, 2013, 06:33		#3
mariam.sara Senior Member Join Date: Jan 2011 Posts: 339 Rep Power: 16	Thanks a lot ghorrocks for the valuable answer I will try follow your recommendations. Currently I only read the tutorial that related to free surface model. I have few questions about your reply hope you illustrate its to me: 1) You said i need first to use the free surface model, which one you mean the homogeneous or in-homogeneous model? 2) With selecting phase change model did you mean I run the problem as single phase flow? if not how i can combine between free surface model and phase change model? Thanks mariam

January 6, 2013, 05:42		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	1) I really think you should answer this question yourself. This is a fundamental decision in terms of the basic approach you are using so if you do not know the answer to this question then you are not ready to proceed anyway. Do further reading and tutorials and you will work it out for yourself. 2) Phase change modelling is inherently a multiphase simulation - so it cannot be run single phase. Just whatever approach you do make sure you start simple, get it working properly, then build on it to make more complex models. If you jump straight into a complex model you will never get it working.