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

摘要： 用有限差分法数值求解一个热、质传递耦合模型，理论研究多孔物料流化床干燥过程。方程离散采用全隐格式的控制容积方法，三对角矩阵法（TDMA）用来求解线性方程组。选用球形的苹果丁作为多孔物料。在典型操作条件下，通过分析温度、饱和度和压力的分布侧形，讨论了物料内部的热、质传递机理。在对比条件下，考察了气体入口温度、气速和床面积因子对干燥过程的影响。结果表明：干燥过程受气、固相间的耦合传热传质的影响十分明显，干燥时间随气体入口温度和气速的提高而减少；随床面积因子的增大而增加。

关键词: 传热传质, 多孔物料, 离散, 流化床干燥