A parabolic cylindrical Stefan problem in vacuum freeze drying of random solids

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 alpha(infinityII) and sample thickness (r(0) - r(1)) on drying kinetics has been discussed. (C) 2003 Elsevier Science Ltd.