Accession Number : AD0289397

Title :   THE ANGULAR DISTRIBUTION OF VAPOR FLOWING FROM A KNUDSEN CELL

Corporate Author : OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS

Personal Author(s) : RUTH, V. ; HIRTH, J.P.

Report Date : NOV 1962

Pagination or Media Count : 1

Abstract : Equations for the spatial distribution and total effusion flow of molecules effusing from a Knudsen orifice by both surface diffusion and vapor transport are developed. The equations are exact, within the assumptions of the model, for knife-edge orifices with small L/R. The equations are only approximate for large L/R. The resultant theoretical predictions agree very well with the experimental observations of Gunther, even for the approximate cases of large L/R. The quantity E, containing both the surface diffusion coefficient Ds and the desorption energy Gds, was found to be equal to 1/20 cm for Gunther's experiments. Consideration of the approximate methods of estimating equilibrium vapor pressures using Knudsen cells indicates that, if surface diffusion and orifice focussing corrections are neglected, the target intercept method should give more accurate results than the total weight loss method for large L/R ratios and vice-versa. (Author)

Descriptors :   *GAS FLOW, *KINETIC THEORY, *MOLECULES, *VAPOR PRESSURE, *VAPORS, DIFFUSION, INTEGRAL EQUATIONS, LOW PRESSURE, SURFACES, THEORY.

Distribution Statement : APPROVED FOR PUBLIC RELEASE