Analysis of Molecular Flow in an Isothermal Enclosure
- 1 May 1963
- journal article
- conference paper
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 38 (9) , 2064-2074
- https://doi.org/10.1063/1.1733934
Abstract
Previously presented analyses of the molecular flow of saturated vapor from a condensed phase in an isothermal enclosure have introduced simplifying approximations early in the treatments. Consequently functions and subtle inconsistencies have appeared which can be recognized, identified, and understood only by returning to the original formulation. A more desirable procedure is to pursue rigorously as far as possible the problem before introducing approximations. The presently described analysis differs from the others in the following respects: (1) The precise system described and the fundamental assumptions employed are defined initially. (2) For a cylindrical (and a generalized) enclosure it is shown that the form p=pe(1—Δ) with pe equal to the equilibrium pressure and Δ a function of the parameters of the cell is a convenient one for the purpose of effecting approximations. (3) The exact physical system corresponding to the classical equation, pe=p[1+(S0/S1)], in which S0 is the area of an orifice and S1 is the evaporating area (both on a spherical surface), has been found to be a spherical enclosure for which Δ can be easily calculated. (4) The single approximation leading to the formulation of Whitman and of Motzfeldt has been found and Δ has been evaluated. An intercomparison is given.Keywords
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