Radiation Heat Transfer in Nonisothermal Nongray Gases

Abstract

Experimental measurements of absorption and emission by nonisothermal CO2 and H2O gases are reported. Analytical formulations and calculations of radiant heat transfer using a simple nongray gas model are presented. It is found that a gray gas model cannot predict even qualitatively the experimental results, while the band model method of calculation yields results in quantitative agreement for total emission and absorption in a band. Effects of line structure are shown to be of secondary importance compared to band envelope structure for line-width-to-spacing ratios above 10−2 in saturated bands. An analytical solution for coupled convection and radiation in a plane-parallel-wall duct is derived to illustrate the utility of the exponential band model for analysis of radiant transfer in nonisothermal, nongray gases.