Water liquid to vapor mass transfer, below boiling temperature
 

Dear Experts;
I am trying to model a vertical water falling film (2 mm Thickness) on a hot plate (90C) and condensate on a plate on the opposite side with a distance 10 mm with air in between.
The water temperature not reaches the boiling temperature (Max. 90C) but a mass transfer should happen between water liquid and air. I think that the Evaporation-Condensation Mechanism shouldn't been used as the water temperature doesn't reach 100C. I Think that I have to use UDF, Am I right? If yes, Could you refer to a tutorial or document that can give me this UDF?

If there are other options, please tell me!!

Best regards