A PARABOLIC CYLINDRICAL STEFAN PROBLEM IN VACUUM FREEZE DRYING OF RANDOM SOLIDS

摘要

A new numerical model for vacuum freeze drying of random solids (e.g. biomaterials, Pharmaceuticals, foods etc.) in the flask was regarded as two-region parabolic moving boundary problem (PMBP) with Robin boundary condition in cylindrical geometry. It takes into account internal resistance of mass transfer in dried region (region Ⅰ) which causes unknown a priori temperature of sublimation T_s and vapor mass concentration C_s at the sublimation front. Numerical model equations in the cylindrical geometry were solved by the MacCormack predictor-corrector method. The effect of both convective heat transfer coefficient α_(∞_(Ⅱ))o and sample thickness (r_0-r_1) on drying kinetics has been discussed.