构建微波冷冻干燥质扩散系数的一种新方法

针对现有微波冷冻干燥模型中必须依靠实验以确定扩散系数的问题．提出一种构建扩散系的新方法。根据毛细管低压气体输运理论，利用物料本身的细微结构、气体分子平均自由程、气体状态参数和气体物性参数来构建扩散系数，在此基础上建立微波冷冻干燥模型。并结合牛肉的微波冷冻干燥行模型可靠性分析。结果表明，新建模型能够很好地描述微波冷冻干燥过程温度场的变化及其特征．升过程干燥曲线的理论值与实验值之间的相对误差小于10％。

A new method to establish mass transfer diffusivity for microwave freeze-drying model

A new method for establishment of mass transfer diffusivity was put forwarded to solve the problem caused by the fact that diffusivity had to be determined by specific experiment in microwave freeze drying model. According to the theory of low pressure gas mass transfer in capillaries, the diffusivity could be expressed as a function of some factors, such as the materiel microstructure, molecule mean free path, vapor state parameters and some vapor physical parameters, based on which the new model for microwave freeze-drying was developed. The analysis of reliability of this model was carded out by the discussion of microwave freeze-drying of beef. The results show that the new model can describe the characteristics of temperature profile in the process of microwave freeze-drying well, and the difference between the drying curves of experiment and that of mode simulation is less than 10% in the stage of sublimation. Therefore, the theory of low-pressure gas mass transfer in capillaries provides a new approach for describing the mass transfer process in microwave freeze drying of capillaceous porous material.