An extended weighted-sum-of-gray-gases model to account for all CO₂ ‐ H₂O molar fraction ratios in thermal radiation

All published weighted sum of gray gases models (WSGGM) were either developed for a limited number of molar fraction ratios, MR, or include MR as a variable in their formulations. Either way, they are not able to adequately support moisture-rich regions of combustion environments, such as the outer regions of unwanted fires, fires during water-based suppression, and some air-injection regions of furnaces. In this article, we provide an extension to a previously published WSGGM by coupling it to a new accurate set of WSGGM coefficients for pure carbon dioxide and water vapor. The coupling follows a linear interpolation methodology, which is justified by a detailed analysis of the line-by-line (LBL) absorption spectra and by plotting the total emissivity of CO₂ ‐ H₂O mixtures with large and small values of MR for various temperatures and path lengths. The proposed model is discussed and validated in four benchmarks, using a solution obtained by LBL integration as reference. The results indicate that, while the previously available WSGGMs either have excessive computational costs or yield inaccurate results in the regions of large MR, the new model can be safely used for all gas compositions in a computationally efficient manner.