Study of heat and mass transfer and stress analysis in wet porous media during freeze- drying process

Abstract

Abstract As people's demand for food quality increases, freeze-dried food is favored due to its ability to maximize the retention of nutrients in food. However, the high cost of vacuum freeze-drying technology forces freeze-dried foods to be generally expensive. In order to improve the freeze-drying efficiency and reduce the cost of freeze-drying process, an in-depth analysis of the stress-strain and heat and mass transfer of materials in the freeze-drying process is quite necessary. In this paper, based on the knowledge of heat transfer, mass transfer and theoretical mechanics, the physical and mathematical model of potato in sublimation drying and desorption drying process was established. The heat and mass transfer, stress and strain of potato slices during sublimation drying and desorption drying were simulated and analyzed using COMSOL Multiphysics version 5.6 software. The results showed that the ratio of potato ice mass to initial ice mass decreased with the increase of drying time. Considering that the simulation ignored the actual situation that steam flowed out from around the potato slices, sublimation drying could actually remove more than 85% or even 90% of the water in the potato slices, and the drying effect was good. The amount of water bound to the potato decreases with drying time. The volume strain of potato in sublimation drying and desorption drying is very small, which is hard to be observed by naked eyes, and the freeze-drying effect is better.