HIGH TEMPERATURE EMISSIVITIES OF THE 2.7 MICRON BAND OF H2O BETWEEN 1000 K AND 2200 K

Spectral emissivities tween 2800 and 4200 waves per centimeter were obtained for water vapor at 1000, 1200, 1500, 1800 and 2200 K. The heated H2O test gas was produced at the exit of a small rocket burner which used H2 and O2 propellants. The emission measurements of the gases were made at the immediated exit of the burner where the composition, total pressures and temperature can be defined. The emissivities or absorptivities were calculated from a calibrated emission spectrum and an accurate spectroscopic determination of the temperature of the test gas. The composition of H2O was evaluated from a semiempirical fit to a thermo-chemical flow calculation. The hot H2O samples were observed at a total pressure of one atmosphere in the optically thin region where the spectral emissivities are on the average approximately 0.05. The variation of the spectral emissivities of H2O in the 2.7 micron region as a function of temperature are given for a constant amount of H2O in the optical path. A good estimate of the integrated intensity of the 2.7 micron H2O band (nu sub 1 and nu sub 3) was made from the high temperature data.