关键词: 传热传质, 多孔物料, 离散, 流化床干燥

Abstract: A mathematical model with coupled heat and mass transfer was solved numerically using the finite-difference technique for a porous material drying process with fluidized bed.The control-volume method with the fully implicit scheme was adopted for discretization of governing equations, and the tri-diagonal matrix algorithm was used to solve the linear equations.Physical properties of apple were applied to the present simulation.Under typical operating conditions, heat and mass transfer mechanisms were analyzed based on the profiles of temperature, saturation and pressure inside the material particles.Effects of gas inlet temperature, gas inlet velocity and bed area factor were examined under different operating conditions.Simulation results show that the main mechanisms for moisture transport during the drying are the capillary flow, evaporation-condensation and transition corresponding to the local moisture levels above its critical value, below the value and in between, respectively.The drying process can be significantly affected by coupled heat and mass transfer between gas and solid phases.The drying time decreases with the increase of the gas inlet temperature and velocity, and the bed area factor.

Key words: heat and mass transfer, porous medium, discretization, fluidized-bed drying