Two-dimensional mathematical modeling of heat and mass transfer in fluidized-bed drying of porous material

A two-dimensional mathematical model of simultaneous heat and mass transfer for porous media drying was derived based on the Whitaker's theory in the present study. The cylindrical coordinate system, which is more practical than the spherical one, was adopted. The model was solved numerically under the circumstance of fluidized-bed drying. The control-volume method with the fully implicit scheme was applied for discretization of governing equations. Physical properties of apple were selected in the simulation. Under typical operating conditions, heat and mass transfer mechanisms were analyzed based on the profiles of temperature and saturation inside the particles. Effects of the temperature, humidity and inlet velocity of hot gas were examined under different operating conditions. Simulation results show that the drying process can be significantly affected by coupled heat and mass transfer between gas and solid phases. The drying time increases with the increase in temperature and velocity of inlet hot gas, and decreases with the increase in humidity and bed area factor.