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

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 gase s model (WSGGM), which replaces the non-gray gas behavior by an equivalent finite number of gray gases, is a simplified model yielding reasonable resu lts. However, a discussion on the weighting factors required for an estimat ion of radiation in a mixture of non-gray gas/gray particulate is not yet e stablished for WSGGM, since they are dependent on the particle number densi ty, particle size distribution: local temperature and partial pressure. Con sequently, the relation between the weighting factors used in the WSGGM for a mixture of non-gray gas and gray particles with scattering in the therma l non-equilibrium has been discussed here, which has not been done before t o the author's best knowledge. Weighting factors for the particles, of whic h temperature is different from that of the gas, were evaluated analyticall y for the WSGGM. The results were, then, validated for the problem of isoth ermal 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, n on-gray gas composition and particle concentration. The effects of thermal non-equilibrium in a mixture of gas and particles were also discussed in pa rallel with scattering effects by particles. Parametric study showed that a variation in the gas concentration yielded a noticeable change in the radi ative heat transfer when the suspended particle temperature was different f rom the gas temperature. New contribution of this study consisted in an ext ension of applicability of the WSGGM non-gray model to two phase radiation. (C) 2000 Elsevier Science Ltd. All rights reserved.