Evaluation of Coefficients for the Weighted Sum of Gray Gases Model

[+] Author and Article Information
T. F. Smith, Z. F. Shen, J. N. Friedman

University of Iowa, Iowa City, Iowa 52242

J. Heat Transfer 104(4), 602-608 (Nov 01, 1982) (7 pages) doi:10.1115/1.3245174 History: Received October 01, 1981; Online October 20, 2009


The weighted sum of gray gases model postulates that total emissivity and absorptivity may be represented by the sum of a gray gas emissivity weighted with a temperature dependent factor. The gray gas emissivity is expressed in terms of a temperature-independent absorption coefficient, absorbing gas partial pressure, and path length. The weighting factors are given by polynomials in gas temperature with associated polynomial coefficients. For absorptivity, a second polynomial for the irradiation temperature is introduced. A regression scheme is employed to fit the model to total emissivity and absorptivity values obtained from the exponential wide-band model. Absorption and polynomial coefficients are reported for carbon dioxide, water vapor, and mixtures of these gases. The model with these coefficients more accurately represents the total properties over a wider range of temperatures and partial pressure-path length products than previously available coefficients.

Copyright © 1982 by ASME
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