Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
Application of the weighted-sum-of-gray-gases model in media bounded by non-gray walls
Submission Author:
Francis França , RS , Brazil
Co-Authors:
Roberta Juliana Collet da Fonseca
Presenter: Roberta Juliana Collet da Fonseca
doi://10.26678/ABCM.ENCIT2016.CIT2016-0377
Abstract
In several engineering applications, such as in combustion problems, the study of the heat transfer by thermal radiation is a very complex task due to the presence of soot, particulates and participating gases. The strongly irregular spectral dependence of the absorption coefficient with the wavenumber, especially at elevated temperatures, makes it necessary to adopt spectral models to determine the radiative quantities. One competitive method, which presents low computational requirement and good accuracy, is the weighted-sum-of-gray-gases (WSGG) model. This method solves the spectral integration of the radiative transfer equation (RTE) by replacing it by a few bands with uniform absorption coefficients, where each one represents a gray gas. In this paper, the WSGG model is applied to a one-dimensional medium slab bounded by perfectly diffuse, non-gray walls. The medium is a homogeneous mixture of carbon dioxide and water vapour, whose radiative properties are taken from HITEMP2010 database. The discrete ordinates method (DOM) is employed to solve the angular integration of the RTE. The wall emission and absorption is characterized by a combination of bands, in which each region of the spectrum presents a specific value of emissivity and absorptivity. The problem is solved as a weighted-sum-of-gray-surfaces, in which, at the end of the calculations, it performs a summation over the contributions of each region. It is made a comparison between the results obtained by the WSGG model and the line-by-line (LBL) benchmark solution to evaluate of the accuracy of the proposed method.
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