Numerical Simulation of Mass and Heat Transfer of Porous Media during Atmospheric Freeze Drying

Abstract:

This research aims to explore the drying behaviors of the saturated frozen porous media during atmospheric freeze drying, which is based on the refrigeration of vortex tube. The experimental study to analyze heat and mass transfer in drying of apples was undertaken numerically. In the numerical part, a twodimensional geometric model of atmospheric freeze drying conditions was constructed by using the software of ANSYS ICEM CFD, and the model was divided into meshes for the computational domain which can make the numerical simulation results clearer. The changes of moisture ratio and core temperature of frozen material was obtained through iterative solution, which was adopted the methods of porous jump model and the finitevolume method(FVM), under different conditions of inlet velocity and radiation temperature. The optimal combination of the parameters was got by means of analyzing the changes of mass and heat transfer of drying sample during different conditions. According to the simulation results of optimal parameters, heat and mass transfer for material can be investigated from velocity field, temperature field, pressure field and the migration of drying area in porous media under different time. In the experimental part, apple slices was applied to drying process. As expected, while drying condition was carried out at a wind speed of 2.5m/s on the inlet and an irrational temperature of 283.15K, experimental values are fitted with the simulated values. The correlation analysis was carried out between experimental and simulated value of material moisture ratio and core temperature through the SPSS-21 analysis software, the R2 value was 0.564 and 0.982 respectively. Such a methodology could be reasonable for studying of freeze drying.