Radiation of Gas Layer over Hot Surface
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Radiation of Gas Layer over Hot Surface1 B. M. Smirnov Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia e-mail: [email protected] Received September 18, 2017
Abstract—A method is presented for evaluation the radiation flux produced by a gas layer near a heated surface, where the gas temperature depends on a distance from the surface. This method refers to small temperature gradients and operates with an effective radiation temperature for each frequency, as well as with the width of the gas absorption band. These parameters are determined by the absorption spectrum of atoms or gas molecules, and also by the shape of the spectral line for the radiative transition between certain states of atomic particles of a gas. The possibilities of this method are demonstrated by examples of emission of photons from the solar photosphere, as well as emission of CO2 molecules in the atmospheres of the Earth and Venus. DOI: 10.1134/S1063776118030093
1. INTRODUCTION The radiative action of a gas near a hard hot surface is manifested in various physical situations, contributing to the energy balance of the surface. We give examples of this kind. Consider a spacecraft or a large meteorite entering the dense layers of the atmosphere. Then the object is heated under the action of frictional forces resulted from interaction with air streams which flow around its surface. In this case, the energy balance of the surface of the apparatus is determined by its heating under the action of air streams passing around it and by radiation of the surface. A high temperature of the surface leads to its partial evaporation, and the evaporated vapor, like heated air near the surface, absorbs radiation from the surface in a certain spectrum range and partially returns it to the surface. Thus, the evaporated material near the surface, like heated air, affects the energy balance of the moving object. A classic example of this kind refers to the greenhouse effect, the nature of which was explained by Fourier in the early 19th century [1, 2] and which is reduced to a partial screening of the surface radiation of a gas located above it. In this case, gas molecules partially absorb the radiation of the surface and return it back. The examples considered below for emission of a gas above the surface refer to the greenhouse effect of planets, namely, Venus and the Earth, due to the emission of molecules of carbon dioxide. The absorption spectrum of carbon dioxide molecules is convenient for demonstration of the greenhouse effect, since, on the one hand, it has a regular structure, 1 The article was translated by the authors.
which simplifies and makes visual operations with it, and, on the other hand, it is quite complex, since it includes a large number of rotational transitions and several vibrational transitions. These examples demonstrate a variety of physical situations and convince us of the inadvisability of using universal programs in the analysis of real situations of this type. 2. RADI
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