An extension of the weighted sum of gray gases non-gray gas radiation model to a two phase mixture of non-gray gas with particles

Abstract

A great deal of efforts has been exercised to date to accurately model the non-gray behavior of the gases. Among others, the weighted sum of gray gases model (WSGGM), which replaces the non-gray gas behavior by an equivalent finite number of gray gases, is a simplified model yielding reasonable results. However, a discussion on the weighting factors required for an estimation of radiation in a mixture of non-gray gas/gray particulate is not yet established for WSGGM, since they are dependent on the particle number density, particle size distribution: local temperature and partial pressure. Consequently, the relation between the weighting factors used in the WSGGM for a mixture of non-gray gas and gray particles with scattering in the thermal non-equilibrium has been discussed here, which has not been done before to the author's best knowledge. Weighting factors for the particles, of which temperature is different from that of the gas, were evaluated analytically for the WSGGM. The results were, then, validated for the problem of isothermal gas containing soot particulates between two parallel slab walls. For further application, the approach derived here was implemented to examine the non-gray radiative effects of the two phase mixture in an axisymmetric cylinder by changing such various parameters as the particle temperature, non-gray gas composition and particle concentration. The effects of thermal non-equilibrium in a mixture of gas and particles were also discussed in parallel with scattering effects by particles. Parametric study showed that a variation in the gas concentration yielded a noticeable change in the radiative heat transfer when the suspended particle temperature was different from the gas temperature. New contribution of this study consisted in an extension of applicability of the WSGGM non-gray model to two phase radiation. (C) 2000 Elsevier Science Ltd. All rights reserved.