I am not sure if I understood properly. I am just a beginner. the walls are adiabatic.

Besides I have another simple heat transfer model between air, sand and biomass. Both sand and biomass are granular. Initial conditions are 300 K. I let it run for sometime. But it is behaving abnormally. The temperature shouldn't drop below 300 K.

The boundary conditions are adiabatic walls, velocity inlet for air, and Pressure outlet.Heat Transfer

Based on this case and the evaporation model case, what do you suggest. Where is the problem? What am I doing wrong.