Numerical Simulation of the Heat Transfer Processes on the Surface and Inside a Polycrystalline SiO2 Sample in an Air Plasma Flow

The following problems of determining the terms of the heat balance equation at the solid–gas boundary are considered: convective heat flux, conductive heat flux, and radiative heat flux when an air plasma flow moves around a heat-resistant material sample. The problems of estimating the catalytic properties of the surface and the contribution of chemical recombination reactions of atoms to the overall heat balance are also solved. A polycrystalline SiO2 sample with known thermophysical properties is taken as the object of study. Since measuring the gas-dynamic parameters of plasma is associated with great difficulties, only the radiative component of a heat flux can be determined experimentally by measuring the sample surface temperature using optical methods. Numerical simulation of the external flow around the sample and its nonstationary heating on a holder allowed us to estimate the convective component of the heat flux and the heat flux density increment caused by the catalytic properties of the surface Δqw taking into account the thermal conductivity of the sample material and radiation from its surface. Calculations are performed using the kinetics of dissociation and exchange reactions in a gas mixture of O2, N2, O, N, NO, O+, NO+, and e– using the Navier–Stokes equations.