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-   -   UDF for condensation problem (http://www.cfd-online.com/Forums/fluent/31227-udf-condensation-problem.html)

 Mahesh April 8, 2003 01:52

UDF for condensation problem

Hi all,

Can anybody tell which standard functions to be used in developing UDF to simulate condensation phenomena

How to take care of water particles in the downstream flow through UDF ?

 majestywzh April 8, 2003 03:00

Re: UDF for condensation problem

i also want to know that.i guess that you case maybe involve water condensation forming ice-particles?my project is the reversing case ,ice-particles melting through the flow.we must write a udf to modify the particle law,accounting for that situation.but additional investigation into the condensation or melting process is still a further challenging effort.

Re: UDF for condensation problem

dear majestywzh,

We have handled the phenomena of ice particle phase change by correcting the specific heat. at the temperature of phase change (32 Deg. f at atm. pressure) we added the latent heat of fusion to the specific heat. we got farely correct results. we have checked the results with the multi-species model.

 majestywzh April 8, 2003 05:50

Re: UDF for condensation problem

Dear prasad , glad to see your response saying that you have handled the ice melting case fairly correctly! i have been involved in this puzzled problem for a long time ,can i have your detailed discription about your method and steps in fluent? can you send it to my hotmailbox?really appreciated for your doing so!

 dinis April 9, 2003 12:39

Re: UDF for condensation problem

I am trying to simulate the ice formation on the surface of a refrigeration heat exchanger since the water vapour content of moist ambient air condensate due to latent heat loss. Is your problem similar? Like to Majestywzh, can you send me the description about the method and steps that you made to create the UDF?

 dinis April 9, 2003 12:41

Re: UDF for condensation problem

(e-mail address presented before is wrong!)

I am trying to simulate the ice formation on the surface of a refrigeration heat exchanger since the water vapour content of moist ambient air condensate due to latent heat loss. Is your problem similar? Like to Majestywzh, can you send me the description about the method and steps that you made to create the UDF?

 roozbeh April 13, 2003 10:22

Re: UDF for condensation problem

Dear Mahesh; You have to use VOF option of the multiphase model. But you should consider that the vof equation in fluent, have not any source term. The existence of a source term in the vof equation, cause the mass transfer from the vapor phase to the liquid phase for the condensation. But in fluent if you want to add a source term to the VOF equation you should add this , to the mass equation of each phase. (for the condensation , add to the mass equation of vapor) These are done by Fluent 6 . Please execuse me for my bad english langauge.

 Mahesh May 2, 2003 09:24

Re: UDF for condensation problem

hi roozbeh,

As far as communication is done,dont mind for langauge(language itself is not bad)..

I am trying the same thing,adding a source for liquid phase and a sink for vapor phase and also energy source too..But I am doing it in Mixture model instead of VOF.

Thanx once again & bye. Mahesh