Do you mean Phase Change model in Fluent or Thermal Phase Change in CFX? In the case of Fluent, this model seems to me to be designed for flash boiling, while for the CFX model, this is a boiling model and it is not for natural evaporation phenomena. If I were to use the boiling model and set a low saturation temperature to force the liquid to vaporize, the mud would remain at that constant saturation temperature during the phase change process, and the effect of relative humidity of the air would not be taken into account.nFlash boiling (flashing) is a process of phase change from liquid to vapor. It distinguishes itself from traditional boiling by the way the liquid gets superheated. It is caused by depressurization or pressure drop instead of heating.nIdeally I would like to implement a model in Fluent like the one described in this image with a mass transfer driven by diffusion in a biphasic case...nn