Leonid Bykov

This article provides a review of the literature devoted to methods of modeling contact heat transfer, as well as the author’s method of numerical modeling and its verification on experimental data.
Based on the analysis of the literature, we draw a conclusion about the determining effect of the roughness of the contacting surfaces on the heat exchange between them. We introduce the concept of a digital double of touching surfaces, that is, a model that takes into account their roughness and allows simulating joint mechanical and thermal interaction between contacting bodies.
We propose a method of numerical simulation of contact heat transfer, the calculation results of which are in good agreement with experimental data.

This article has developed a method for calculating the emissive characteristics of water vapor in the region of $6.3$ $\mu $m under conditions of nonlinear thermal nonequilibrium. A formula is presented for calculating line intensity for various combinations of translational, rotational and vibrational temperatures. When calculating the vibrational energy, the harmonic oscillator model was used. To calculate the rotational energy of H$_2^{}$O, the molecule of which is an asymmetric top, the model of the effective rotational Hamiltonian was used. A solution to the radiation transfer equation is obtained in the absence of scattering, when the medium is capable of both emitting and absorbing radiation. Test calculations were carried out for three temperatures: $600$ K, $1000$ K, and $1550$ K. A comparison of the calculation results with experimental data on the transmittance of a homogeneous H$_2^{}$O layer showed satisfactory agreement. An analysis of the influence of thermal nonequilibrium on the emissive characteristics of a homogeneous H$_2^{}$O layer was carried out for various combinations of translational, rotational and vibrational temperatures for high and low pressure values. It is shown that, in this spectral range, thermal nonequilibrium has a very weak effect on the transmittance of the layer, but very strongly affects the nonequilibrium Planck function, which behaves significantly nonlinearly with respect to characteristic temperatures and cannot be described by any of the temperatures of the energy modes: translational, rotational and vibrational. The values of the nonlinear non-equilibrium Planck function in the range $1000$–$1800$ cm$^{-1}$ are closest to the radiation of the black body at a translational temperature that coincides with the value of the vibrational temperature of the second energy mode — $T_{v2}^{}$. This is due to the fact that in the region of $6.3$ $\mu $m the main mechanism of radiation generation is the spontaneous deactivation of the H$_2^{}$O deformation mode. Accordingly, the influence of thermal nonequilibrium on the spectral energy brightness is great. This important result makes it possible to significantly simplify the calculation of emission characteristics when using such simplified approximate methods as the statistical model of the band, the $k$-distribution method since, in fact, the databases created for these techniques only need to take into account the effect of disequilibrium on the Planck function.