August 16, 2023 at 12:01 pm
Atharva Nagarkar
Subscriber

Hello,

Please refer to the UDF Manual for detailed explanation on the DEFINE_EXCHANGE_PROPERTY macro. I have attached the link below for your reference. Check section 2.4.3 as well as example 3 (section 2.4.3.5) which is related to your topic. As per the manual, the UDF will need to return the real value of the effective heat transfer coefficient to the solver. So, if the quantity being modeled by your UDF depends on the interfacial area, your UDF should return the coefficient multiplied by the interfacial area.

2.4. Multiphase DEFINE Macros (ansys.com)

As per the Fluent Theory Guide, for the Ranz-Marshall model, the relative Reynolds number is based on the diameter of one phase which is liquid in your case. The Prandtl number is defined for the other phase which must be gas. Please check the section 14.5.17.1.3 of the Theory guide, the link of which is given below.

14.5.17. Description of Heat Transfer (ansys.com)

If you are not able to access the links, please refer to this forum discussion: Using Help with links (ansys.com)

Thanks!