真空冷冻干燥技术常用来生产高品质的冻干白蘑菇，但其能耗大、干燥时间长的缺点限制了其推广应用。与传统冷冻干燥技术相比，微波冷冻干燥可节约干燥时间和能耗，同时可保持其冻干产品的特点。微波冷冻干燥过程的质热传递现象极为复杂，其过程的预测对干燥过程的控制至关重要。此外，目前国内外对于微波冻干过程的传热传质模拟都未考虑物料介电损耗因子变化会导致其微波吸收特性的改变，故模拟结果都不甚理想。本文通过矢量网络分析仪对白蘑菇介电特性进行精确测定，得出白蘑菇介电损损耗因子相对其温度和水分含量的回归方程；在此基础上利用较为通用的升华-冷凝模型对微波冻干过程质热传递进行了数值模拟研究，通过白蘑菇微波冻干试验验证，表明考虑了介电特性的微波冻干质热传递模型可对物料温度分布进行较准确的预测。

Vacuum freeze drying technology is often used to produce high quality dried white mushrooms, but its disadvantages of high energy consumption and long drying time limit its application. Compared with conventional freeze drying technology, microwave freeze drying can greatly save drying time and energy consumption, while retaining the characteristics of the freeze dried products. The process of heat and mass transfer during microwave freeze drying is very complicated, and the precise prediction of the heat and mass transfer is important for control of the drying process. In addition, international and domestic reports on the simulation of heat and mass transfer during microwave freeze drying have not considered that a material’s dielectric loss factor can lead to variation in microwave absorption ability, resulting in imprecise simulation results. In this study, a vector network analyzer was used to determine the dielectric properties of the mushrooms and a regression equation of dielectric loss factor versus temperature and moisture content was generated. Based on the dielectric property, a numerical simulation of heat and mass transfer during microwave freeze drying was carried out using a commonly used sublimation-condensation model, and was experimentally verified by conducting microwave freeze drying on white mushrooms. The results show that the simulation of heat and mass transfer based on dielectric property can precisely predict the temperature distribution of the samples during microwave freeze drying.

国家自然科学基金（U1204332）