[Piotr95]

Hello,

I have an issue with the simulation of water condensation in humid air flow. I did the single-fluid / single-phase model, where the liquid water and humid air are threaten as a mixture. The properties of the mixture such as the specific heat, gas constant etc. which depend on the pressure, temperature and relative humidity are defined by UDRGM. Values needed for their computations, such as humid density, are being calculated in second DEFINE_ADJUST UDF and are being transported to the UDRGM via UDMI. It works perfectly.

I'm facing some problems when switching to the multi-phase model. In the multi phase model the air and water vapor, are threaten as a mixture (humid air) and the water droplets are dispersed phase. The water properties are defined via Fluent GUI, as the density, specific heat etc. changes due to pressure and others factors are irrelevant. The UDRGM is hooked only for the humid air. Unfortunately, the boundary gets crazy, after turning the calculations on, the temperature at the inlet is 1K. The solver gives an error, that Cp on the inlet is equal to 0, although in the results section, it gives proper values of CP. The problem appears also if the Cp is constant, written in UDRGM.

PS. if it is relevant, i have some UDS in both models, to track other conservative variables.

Do anybody have any idea how to solve it?

Regards
Piotr