Non luminous gas radiation - Approximate emissivity models
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The main sources of non-luminous gas radiation in furnaces are carbon dioxide and water vapor. Approximation of the standard emissivities of water vapor and of carbon dioxide by mixed gray-gas model is studied. The model developed for carbon dioxide standard emi s si vi ti es covers a range of temperature of 3DO-1BOOK and a partial-pressure-length product range of 0.01 to 10 m atm. A mixture of six gray gases was adequate to cover the whole range. For the water vapor thermal radiation two models were developed to approximate the standard water ~apor emissi~ities. In the first model water ~apor is approximated by a mixture of four gray-gases and can be used in the temperature range of 300-700K and the partial-pressure-length range of 0.01 to 2 m atm. The second model is a piece-wise one in which one gray gas is used to cover the pL range 0.5-2 m and a second gray gas covered the range of 0.05-0.5 m. The model may be used in the temperature range of 700-l500K and has an error range of -2.3 to 3.7~.