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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
A wide-band formulation based on the gray gas model applied to non-isothermal and homogeneous water vapor media
Submission Author:
Roberta Juliana Collet da Fonseca , RS
Co-Authors:
Roberta Juliana Collet da Fonseca, Guilherme Crivelli Fraga, Francis França
Presenter: Roberta Juliana Collet da Fonseca
doi://10.26678/ABCM.ENCIT2020.CIT20-0269
Abstract
Modeling thermal radiation in participating gases is a complex task due to the highly irregular behavior of the absorption coefficient with the wavenumber, principally at elevated temperatures. In this framework, simple spectral models, such as the gray gas (GG) model, have received much attention for presenting an alternative to the spectral integration of the radiative transfer equation (RTE) with low computational effort. This paper proposes a methodology that aims to improve the GG model by dividing the spectrum into a set of intervals for which individual absorption coefficients are determined. The RTE is solved for each spectral interval separately using the GG approach and the total quantities are obtained by the summation of the contributions in each one of these segments. The obtainment of each set of coefficients is based on curve adjustments of the Planck-mean absorption coefficients from data extracted from the HITEMP2010 database. To test the methodology, absorption coefficients for water vapor are determined for each selected band. The accuracy of the resulting model is assessed for radiative transfer calculations in a one-dimensional homogeneous, non-isothermal medium slab bounded by black walls. Results are compared with those obtained employing other GG coefficients of the literature and the LBL solution.
Keywords
thermal radiation, Planck-mean absorption coefficient, gray gas model, line-by-line integration, spectral intervals
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