Heat and mass transfer during drying of granular products — simulation with convective and conductive boundary conditions

Numerical simulation of grain drying in a vertical cylindrical bed has been carried out with specific boundary conditions: evaporation, which occurs with forced air flowing through the bed, is intensified with a conductive heat flux from the wall. We consider two mathematical models of heat and mass transfer through granular medium: two temperature model (No Local Temperature Equilibrium Model: NLTEModel) and one temperature model (Local Temperature Equilibrium Model: LTEModel). The air–grain mass transfer is expressed with a drying rate equation outcome from experiments. The resolution of the equations set is carried out, using a finite volume method. Different effects, such as the effect of the porosity variation on energy and mass transport, are discussed. Sensitivity to external conditions is determined. Finally, validity of local thermal assumption is examined.