Comparative Measurements of Tangential Momentum and Thermal Accommodations on Polished and on Roughened Steel Spheres.

摘要

The research reported here was conceived as an initial attempt to bring experimental knowledge of tangential momentum accommodation of isotropic gases on controlled surfaces to a stage of development comparable with that found in the thermal accommodation field. Measurement of the drag torque experienced by spinning objects held in practically frictionless magnetic suspension when immersed in low pressure gases has been used to measure the tangential momentum accommodation coefficient, sigma. All precise determinations of the thermal accommodation coefficient, alpha, have been made on fine filament systems so it was necessary to devise new means to determine alpha on the same surfaces of the relatively massive objects as are used for sigma determination. The method described in this paper is original, so far as we know, when applied to measurement of alpha on metal surfaces at low gas pressure. (Author)