Eventos Anais de eventos
ENCIT 2018
Brazilian Congress of Thermal Sciences and Engineering
Evaluation of the WSGG model accuracy as a function of path length in non-isothermal, non-homogeneous media
Submission Author:
Felipe Ramos Coelho , SP
Co-Authors:
Felipe Ramos Coelho, Guilherme Crivelli Fraga, Francis França
Presenter: Felipe Ramos Coelho
doi://10.26678/ABCM.ENCIT2018.CIT18-0123
Abstract
This study evaluates the weighted-sum-of-gray-gases (WSGG) model accuracy for mixtures of CO2 and H2O, with path lengths ranging from 0.25 to 30 m, in non-isothermal, non-homogeneous conditions. The WSGG coefficients from several authors are used considering a mixture with fixed mole ratio of 2/1, representing typical products of stoichiometric combustion of methane in air. Previous results show that all the coefficients are capable of accurately predicting emittance data when compared to the line-by-line (LBL) benchmark solution for the whole path length range. However, radiative heat flux and volumetric source validation was only performed for a limited number of path lengths. The main objective of this study is to extend these calculations for a path length range of 0.25 to 30 m and understand how both quantities are affected by it. Results show how the WSGG normalized average deviations from the LBL benchmark vary as a function of path length. These normalized deviations are then used to determine path length ranges of applicability (PLRAs) for all the WSGG coefficients, aiming to obtain a maximum of 5% normalized average deviation for both radiative heat flux and volumetric source. A second approach is also employed to obtain PLRAs considering a maximum average deviation of 10%. Results show that the radiative heat flux is the limiting factor for determining the WSGG coefficients PLRAs, since deviations are overall higher than those of the radiative volumetric source. Furthermore, this study shows that most WSGG coefficients were applicable to the whole path length range when solving isothermal and homogeneous conditions, but only a few had wide PLRAs on non-isothermal and non-homogeneous conditions, even when considering maximum average deviations of 10%. As a consequence, the PLRAs for radiative heat flux and volumetric source calculations are overall smaller than those recommended by other authors based on total emittance results, emphasizing the importance of studying the path length effect on the WSGG accuracy and applicability.
Keywords
WSGG, LBL, path length, ranges of applicability, HITEMP2010
