Improvement of the efficiency of the superposition method applied to the WSGG model to compute radiative transfer in gaseous mixtures

Abstract

A new method for the treatment of radiative heat transfer in mixtures of participating species in the framework of the weighted-sum-of-gray-gases (WSGG) model is proposed, based on a modification of the existing superposition method. This new approach allows for a reduction in the number of times that the WSGG radiative transfer equation must be solved by decreasing the total number of gray gases that needs to be considered for modeling the mixture. Although it may be extended to mixtures of any number of species, in this paper the new method is only applied to water vapor-carbon dioxide mixtures. The reference for the comparisons is provided by line-by-line (LBL) integration of absorption spectra generated from a high-resolution spectral database. Results show that the method does not yield a loss in accuracy relative to the standard superposition method, and performs better than an existing WSGG model developed for H2O−CO2 mixtures with varying mole fraction ratio. There is also a reduction of about 50% in the computational time required for the solution compared to the original superposition method, thus making the new method more efficient and more competitive in relation to other methodologies for modeling radiative transfer in non-homogeneous mixtures.