马铃薯升华干燥过程中的仿真研究

目的 为了了解马铃薯升华干燥效果和马铃薯的升华干燥时间，优化冻干过程，减少冻干能耗，采用COMSOL Multiphysics软件对马铃薯切片进行模拟。方法 综合利用传热学、传质学和有关学科知识，建立马铃薯切片在升华干燥过程中的物理模型和数学模型，模拟马铃薯片的升华干燥过程。结果 冰质量与初始时刻冰质量之比随着干燥时间增加逐渐减少，脱水速率随着干燥时间增加逐渐减小。考虑模拟忽略了蒸汽从切片四周流出的实际情况，导致冰质量与初始时刻冰质量之比实际值小于模拟值，脱水速率实际值高于模拟值。实际上升华干燥能除去马铃薯切片85%以上甚至90%以上的水分，干燥效果较好。随着马铃薯切片厚度的增加，马铃薯切片的升华干燥时间逐渐增大。马铃薯升华干燥时所处的冻干仓温度越高，升华干燥完成时所用的时间越少。冻干仓压力越大，马铃薯升华干燥时间越长。隔板温度越大，马铃薯的升华干燥时间越短。结论 在对马铃薯进行冻干时，应尽量增加冻干仓温度，降低冻干仓压力，增加隔板温度，减小马铃薯厚度，以降低马铃薯在冷冻干燥过程中的能耗。

Simulation Study on Sublimation Drying Process of Potatoes

Objective In order to understand the sublimation drying effect and sublimation drying time of potatoes optimize the freeze-drying process and reduce energy consumption during freeze-drying the COMSOL Multiphysics software was used to simulate potato slices. Methods By integrating knowledge of heat transfer mass transfer and related disciplines a physical model and a mathematical model of potato slices during the sublimation drying process were established to simulate the sublimation drying process of potato slices. Results The ratio of ice mass to initial ice mass gradually decreased as the drying time increased and the dehydration rate gradually decreased as the drying time increased. Considering that the simulation neglected the actual situation of steam flowing out from around the slices the actual value of the ratio of ice mass to initial ice mass was lower than the simulated value and the actual dehydration rate was higher than the simulated value. In fact sublimation drying could remove over 85% or even over 90% of the moisture from potato slices resulting in a good drying effect. As the thickness of potato slices increased the sublimation drying time of potato slices gradually increased. The higher the temperature in the freeze-drying chamber during potato sublimation drying the less time was needed for sublimation drying to be completed. The greater the pressure in the freeze-drying chamber the longer the sublimation drying time of potatoes. The higher the temperature of the partition the shorter the sublimation drying time of potatoes. Conclusion When freeze-drying potatoes it is advisable to increase the temperature of the freeze-drying chamber reduce the pressure in the freeze-drying chamber increase the temperature of the partition and decrease the thickness of the potatoes to reduce the energy consumption during the freeze-drying process.