Effects of the Sample´s Porous Structure on the Process of Vacuum Freeze Drying

In the typical operation conditions of vacuum freeze drying, the relationship between the diffusion mass transfer and the sample´s porous structure is analyzed. The heat and mass transfer models of the freeze drying are setup, and numerically solved by the finite volume method with fixed grids. The results show that the drying processes are significantly influenced by structural parameters, the diameter and tortuosity of sample´s pores, so structure analysis is necessary for the process optimization of the freeze drying. Moreover, it may provide an effective way to improve the drying efficiency through the investigation of the pre-cooling stage of the freeze drying.