THE KINETICS OF HEAT TRANSFER USING EXPERIMENTAL DATA OF MOISTURE EXCHANGE IN THE PROCESS OF CONVECTIVE DRYING OF THIN FLAT MATERIALS

The results of studies of drying of thin flat materials by method regular thermal regime are presented. The results of experimental data processing using generalized complex variables are shown. The approximate empirical equation for calculating the heat flow density, the duration of the drying process and the temperature of material at the period of decreasing rate were obtained by processing and analysis of experimental data. The article also indicated kinetics drying calculation with the experimental data of moisture exchange and without the use of criteria heat exchange equations. The equations for determining the rate of heating of the wet material and the rate of decrease in moisture content were obtained by the authors for a group of thin flat materials. The paper demonstrates that the regularization in the drying process takes place not only for temperature and moisture content, but also for thermal flow. An analysis of drying of thin flat materials by the magnitude of the Biot heat exchange criterion in the period of the decreasing drying rate was performed. It was found that in the second drying period, the Biot number is less than 1 and takes the values 0.2–0.5. It is established that the rate of heating of wet material does not depend on the drying regime and the thickness of the material. Analysis of drying curves showed that the rate of moisture content loss is a complex function of the drying regime, initial moisture content, drying speed in the first period, and a number of factors affecting the process. The processing of experimental data on the basis of generalized stable complex variables, which represent the most general regularities of the kinetics of drying, makes it possible to obtain fairly simple and reliable approximate equations for the calculation of heat and moisture exchange in the drying process. The inaccuracy with this method of processing the experiment is within 3–5 %. Validation of the estimated equations and comparison of the numerical values of the heat flows the temperature and duration of the drying process with the experiment were implemented. 

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