The spectral line weighted-sum-of-gray-gases (SLW) model for prediction of radiative transfer in molecular gases

Abstract

Abstract This review documents the history and theoretical development of the Spectral Line Weighted-sum-of-gray-gases (SLW) model. The SLW model is a so-called global engineering model for prediction of radiation transfer in gaseous media. The model bases the gas radiative properties on local thermodynamic properties (temperature, species concentration, etc.), and has been developed for use with any arbitrary solver of the Radiative Transfer Equation (RTE). This review first presents the fundamental groundwork for the SLW model, followed by the detailed theoretical development of the model with associated publication references. The model was first formulated for isothermal, homogeneous single-component gases. As part of this formulation a new gas property distribution function, the Absorption Line Blackbody Distribution Function (ALBDF) was proposed, and the ALBDF has been generated from detailed spectroscopic databases for H2O, CO2, and CO over a range of gas temperature, mole fraction (where appropriate), and total pressure. The SLW model was then extended to treat non-isothermal, non-homogeneous gases, mixtures of gas species, and model application in scenarios featuring non-gray particulates and/or boundaries. In all of its development the SLW model has been rigorously tested against benchmark line-by-line spectral integration solutions of the RTE using the same spectroscopic database as used in the generation of the ALBDF. Work continues on the refinement of the SLW model, enhancing its accuracy in prediction of radiative transfer. Finally, this review will summarize work-to-date utilizing the SLW model in coupled heat transfer scenarios—comprehensive combustion simulations, combined natural convection and radiation, etc.