Cheilytko A. 3. Development of theoretical foundations for the formation of thermophysical properties of heat-insulating materials by controlling the processes of heat and mass transfer in porous structures

3. The dissertation is devoted to the complex problem solving of the formation of thermophysical properties of thermal insulation materials by controlling heat and mass transfer processes in porous structures with the purpose of creating new and improving existing porous heat-insulating materials and structures from them for thermal protection of elements of industrial power plants. We have further developed the study of the dynamics of formation of the porous structure of alumina materials. Functional relationships of technological parameters and structural characteristics of a porous material (number and size of pores) are determined. A mathematical description of the formation of a closed spherical pore that was formed due to the chemical reaction and the thermodynamic parameters of the gas in it was realized. A complex experimental study was performed with computer simulation of the effect of the porous structure on the effective coefficient of thermal conductivity of highly porous materials. A generalized equation for the effective thermal conductivity of a porous material was found, which made it possible to develop a technique for predicting thermophysical parameters from a porous structure. In the work the methodology of creating porous materials with optimal thermophysical properties is developed due to the change of porous structure at the stage of formation of materials and the proposed technological processes for the creation of high-quality products of refractories and expanded clay. Also, for the special conditions of operation, the method of creating an element of thermal protection construction from metal and composite materials is proposed. The obtained equations for determining the effective coefficient of heat conductivity of porous structures with closed and open porosity including the calculation of the thermal permeability coefficient and the geometric characteristics of the porous structure are based on the theory of heat energy transfer by fluids. The geometrical characteristics of the porous structure and the thermal permeability of fourteen porous heat-insulating materials were found.