Learning Forum

[Navsing]

Hi,nI'm trying to use the DEFINE_MASS_TRANSFER UDF macro example in the manual just to have a working example which I will then modifiy later on for my own problem.nHowever, when I used example in the manual and run my simulation, no phase change occurs. Specifically, no condensation occurs, which should happen as I have an outer pipe wall set at a temperature of 50 K lower than the temperature of my vapour patched in the fluid domain which is set at saturation (373.15 K).nI notice that the UDF example in the manual is basically just Lee's model which is already implemented in fluent. When I use the default Lee's model in the evaporation-condensation section, my simulation runs completely fine and condensation occurs.nnSo what could be the problem in the case of the UDF?n

[DrAmine]

Yes that is the same as the Lee Model. Are you hooking the function too? Can you you show your panel? Which version are you using?n

[YasserSelima]

As a first step, I would print Message inside the function showing T, Tsat and the mass and see if the values make sense to me or not. n

[Navsing]

I'm using ANSYS 2020R1 version. Yes I'm hooking the UDF as stated in the manual, and these are my panels:n

[Navsing]

And I've looked at the temperature contours and they seem fine. I am observing a temperature gradient across the wall. I am seeing a mass transfer gradient as well however it is quite small. n