A.M. Afanasiev Dr.Sc.(Eng.), Associate Professor, Professor Department of Information Security, Volgograd State University, Institute of Priority Technologies V.K. Mikhailov Ph.D.(Chem.), Associate Professor, Faculty of Electronics and Computer Engineering Volgograd State Technical University B.N. Siplivy Dr.Sc.(Eng.), Professor, Physico-Technical Institute, Deputy Director of the Physico-Technical Institute of Science, Volgograd State University

The proposed system of equations and boundary conditions that simulate the processes of heating and drying heterogeneous wet sample electromagnetic radiation. Heterogeneity is caused by the dependence of the diffusion coefficients of heat and moisture from temperature and moisture and has a layered structure. The constant thermophysical characteristics is one of the main ap-proximations in the modeling of the influence of electromagnetic radiation on a wet environment, and it is traditionally used in re-search, but the validity of this approach still has not been proven. The urgency of this problem becomes apparent when referring to experimental facts, which point to a substantial change in the properties of moist materials during their heat treatment. Thus, the thermal conductivity of clay may change during the drying 3.5 times, and the coefficients of diffusion and thermal diffusion of moisture in 10 and more times. The paper describes a numerical algorithm to account for these changes. In addition to the heterogeneity of the environment, the mathematical model considers the following factors: the density of the heat loss is determined by the heat transfer by convection and heat radiation, and the intensity of mass transfer to the surface of the material with the environment depends on the difference of partial pressures on both sides of the boundary layer; the temperature field inside the material is determined by the heat transfer due to the phenomenon of heat transfer by evaporation of the liquid (vapor), and the presence of internal heat sources caused by the absorption of the penetrating electromagnetic radiation; transfer moisture within the material is partly in liquid and partly in the form of steam, and is caused by moisture gradients (diffusion) and temperature (thermal diffusion). Boundary conditions of heat and mass transfer are linear and the equations describing the distribution of heat and moisture in the sample is quasilinear (taking into account the dependence of the thermophysical characteristics of the material from temperature and moisture content). The solution to this initial value problem can be done only by numerical methods. On the basis of experimental data of a selected approximating expressions describing the dependence of the thermophysical cha-racteristics of the material from temperature and moisture content. For the case of one spatial variable, we developed an original scheme for the numerical solution of initial-boundary value problem for the fields of temperature and moisture content, which is based on the approximation of the second derivative by the method of A.A. Samarsky (integro-interpolation method), a two-layer symmetric scheme of crank-Nicholson method and driving. The criterion for stability of this scheme. Numerical experiments are carried out for materials with different sets of thermophysical characteristics, the comparison of the results for the numerical schemes with constant and variable coefficients of the transfer. It is shown that, depending on the type of material, the calculation schemes with constant and variable coefficients can lead to differences of a fundamental nature that the decisive way may affect the organization of the process of electromagnetic processing of materials. The results of the study can be used to optimize various technical devices that use the processes of heating and drying electro-magnetic waves: technological lines for dehydration of food products and agricultural raw materials, instruments for infrared ir-radiation of biological tissues in medicine, devices for hyperthermia of biological tissues in Oncology.

 

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