Experimental and simulation studies of primary vacuum freeze-drying process of random solids at microwave heating

摘要

This paper concerns experimental and theoretical studies of freeze-drying process at microwave heating. Two kinds of random solids were dried: material which are assumed to have no internal porosity (ground glass), as well as one containing internal porosity (Sorbonorit 4 activated carbon). Formulated one-dimensional two-region model of freeze-drying process at microwave heating takes into account unknown a priori sublimation temperature T_s(t) and mass concentration of water vapor C_s(t) at moving ice front. Steady capacity of internal heat source is correlated with electric field strength E and dissipation coefficient K(T) in both regions of the material to be dried. Linear temperature dependency of dissipation coefficient is assumed and described by two regression parameters: μ_(1_i) and μ_(2_i) for dry (i=Ⅰ) and frozen (i=Ⅱ) bed, respectively. A correlation between both measured and calculated temperatures of the sample and actual electric field strength was observed. Fairly good agreement between experimental and simulated results was stated.