Accession Number:

AD0289397

Title:

THE ANGULAR DISTRIBUTION OF VAPOR FLOWING FROM A KNUDSEN CELL

Descriptive Note:

Corporate Author:

OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS

Personal Author(s):

Report Date:

1962-11-01

Pagination or Media Count:

1.0

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 LR. The equations are only approximate for large LR. The resultant theoretical predictions agree very well with the experimental observations of Gunther, even for the approximate cases of large LR. The quantity E, containing both the surface diffusion coefficient Ds and the desorption energy Gds, was found to be equal to 120 cm for Gunthers 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 LR ratios and vice-versa. Author

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Distribution Statement:

APPROVED FOR PUBLIC RELEASE