The absorption coefficient of participating species, such as CO2 and H2O, shows very irregular dependence with the wavenumber, which makes it difficult the spectral integration of the radiative transfer equation (RTE). This task can be performed with the line-by-line (LBL) integration, which is very computationally expensive due to the vast amount of spectral lines that span the spectrum. As alternatives to the LBL integration, there are global models, such as the weighted-sum-of-gray-gases (WSGG) and the spectral line weighted-sum-of-gray gases (SLW). These models replace the integration with respect to the wavenumber by the summation over a certain number of gray gases, thus reducing the computational effort. This paper shows a modification of the WSGG model, in which the absorption and emission coefficients of each gray gas are considered to be function of the temperature. The model, named WSGG with non-constant coefficients (NCC-WSGG), is applied to solve a few non-isothermal and non-homogeneous problems. The results show very satisfactory agreement with the LBL integration.

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