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An apparatus for measuring the rate of diffusion of gases through porous solids at elevated pressures

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Title: An apparatus for measuring the rate of diffusion of gases through porous solids at elevated pressures
Author: Han, Agnes Yu-Wen
Degree Master of Applied Science - MASc
Program Chemical and Biological Engineering
Copyright Date: 1959
Subject Keywords Diffusion; Gases; Permeability; Chemical apparatus
Abstract: An apparatus utilizing a constant pressure flow system was developed for measuring the effect of pressure on the diffusion rates, and therefore diffusion coefficients, of binary gas mixtures passing through porous solids. Hydrogen and nitrogen were employed for testing ceramic porous solids at room temperature, with various pressures from 1 to 14.6 atmospheres absolute. The values obtained for the products of the effective diffusion coefficients and absolute pressures were substantially constant, with a maximum deviation of ±5%. It seemed that the diffusion rate of hydrogen increased with pressure, while that of nitrogen decreased. At atmospheric pressure the ratio of diffusion rates {N(H₂)/N(N₂)} was in good agreement with the theoretical value proposed by Hoogschagen i.e. √M(N₂)/M(H₂). However, the experimental diffusion ratio increased with pressure. This behavior might be due to some degree of forced flow present in the diffusion process, although it was not possible to determine a cause for such a flow. This apparatus is suitable for the study of diffusion rates in the transition region, between Knudsen and ordinary diffusion, by simply changing pressure and hence the mean free path of the gases involved. Forced flow would not be a factor in this region.
URI: http://hdl.handle.net/2429/41047
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]
Scholarly Level: Graduate

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