MEASUREMENTS OF FREE MOLECULE HEAT TRANSFER IN AIR AT MACH NUMBERS FROM 10-18

Heat transfer measurements to fine wires in the freemolecule flow regime at Mach numbers typical of the conditions in which satellites move were made. Accommodation coefficients obtained within the accuracy of these experiments agree with those obtained at much lower Mach numbers. The heat transfer measurements taken indicate no Mach number effect. At high Reynolds numbers, where free-molecule flow is no longer obtained, agreement with previous data is reasonable down to Knudsen number equal to one, corresponding to Reynolds number of 5 or less. A further decrease in the Knudsen number concomitant with an increase in the Reynolds number yields heat transfer rates that are somewhat lower, although in essential agreement, with previously acquired data. With an appropriate calibration for the degree of rarefaction of the gas, a wire probe shows promise as a fast reacting instrument for use in gas flows of quite low density. (Author)