The spectral and total emissivity of carbon dioxide

The calculation of radiative heat transfer from flames and combustion gases requires, in the general case of non-homogeneous gases, a knowledge of the spectral characteristics of the gases. In this paper an analysis is made of available spectral data on carbon dioxide, extended with an approximative description of the 15-μm, 10-μm, and 2-μm bands, in the form of a comparison with measured total emissivities. The contribution of the bands to the total emissivity is shown at various temperatures and path lengths. The spectral emissivity is expressed as mean-values over wave-number intervals by means of the statistical band model. The agreement between Hottel\u27s diagrams of total emissivities and the total emissivities calculated on the basis of spectral data is good for optical path lengths greater than 1.0 cm atm. If Hottel\u27s values are corrected in the small-path length region for the possible influence of carbon dioxide in the air layer between the measuring instrument and the gas container, there remains a discrepancy of less than 15% around path lengths of 0.1 cm atm