Moisture exchange kinetics and temperature during the process of convective drying of thin flat wet materials

The basic laws of drying kinetics of thin flat materials during the falling drying rate are outlined. A method for calculating the average integral temperature of wet material on the basis of the relative temperature coefficient of drying is presented. Experimental data were processed based on the obtained values of the relative drying rate in the drying processes of ceramics, asbestos, and woolen fabric. A formula for calculating the average temperature is proposed. The solution of the differential equation of heat conduction for a wet plate in the process of drying (falling velocity period) with boundary conditions taking into account drying conditions is given. The calculation of the heat transfer coefficient is presented. Based on the study of many sources and processing of experimental results, formulas for calculating the coefficient of thermal conductivity of wet materials are presented. The analytical solution of the problem confirmed that during convective drying in low-intensity processes of the second drying period, the temperature change with a decrease in moisture content changes from an exponential dependence to a linear one, which is in full agreement with the experiment. A comparison of the temperature calculation by the experimental formula with the results of analytical solutions is presented. The analytical solution confirmed the laws established experimentally. Quite reliable coincidence of experimental and calculated analytical values of temperature for the period of falling speed drying of ceramics, asbestos, and fabric is obtained. The results of comparing experimental temperature values with calculated analytical values indicate a wider application of differential heat transfer equations for practical tasks of drying various wet materials.

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