Problems in Effusion

Author: Stockmair, Wilfried

Year: 1959

Degree: Engineer's thesis

Advisors: Liepmann, Hans Wolfgang; Cole, Julian D.; Plesset, Milton S.

Committee Member: Unknown, Unknown

Option: Aeronautics

DOI: 10.7907/KH55-XN11

Abstract

The flow of rarefied gases from a vessel through an orifice into vacuum is studied here. Special conditions of this study are that the mean free path of the molecules is of the same order of magnitude as the hole diameter; furthermore the thickness of the wall is neglected. Knudsen [1,2] investigated this effusion problem for constant conditions throughout the gas, assuming Maxwellian velocity distribution and very large mean free paths. In the present study the influence of a one-dimensional temperature gradient extending from the wall upstream into the gas is investigated. Formulae for the massflux and the spatial intensity distribution of the outflowing molecules are calculated for steady flow conditions. Finally the behavior corresponding to a nonstationary temperature gradient (according to suddenly heated or cooled wall) is studied.

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