Complex generalized variables of drying kinetics in the process of convective drying of wet materials

The article presents experimental data processing methods based on generalized stable variables of the drying kinetics of thin, flat, wet materials. The following complex variables were adopted for processing experimental data during convective drying of ceramics, sheet asbestos, felt, and cardboard: generalized drying time, ratio of drying time by periods, ratio of current moisture content to critical moisture content, and relative drying rate. Generalized variables in the drying process, regardless of the drying mode, characterize the most general patterns of drying kinetics. The processing results are presented as a dependence of the relative drying rate on the adopted variables. Equations for drying duration with a minimum number of constants determined empirically are obtained. Based on the heat balance equation for the period of decreasing drying rate, equations for calculating the temperature in the second drying period are given. As a result of processing the drying rate curves for ceramics, asbestos, and felt, the dependence of the relative drying rate on the relative moisture content is obtained. An equation is presented for determining the heat flux density in the second period of drying rate and relative moisture content. A validation of the resulting equations is presented. The error between the calculated and experimental values  is within the accuracy of the experimental data processing, up to 10 %. The presented approxi- mate methods for calculating drying kinetics, obtained by processing experimental data with generalized complex variables, are of interest for the practical drying of capillary-porous wet materials.

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