NON LUMINOUS GAS RADIATION: APPROXIMATE EMISSIVITY MODELS
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 emissivities covers a range of temperature of 300-1800K 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 vapor emissivities. In the first model water vapor 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 700-1500K and has an error range of -2.3 to 3.7%.