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Diffusional boundary‐layer resistance for membranes with low porosity
Author(s) -
Malone Dermot M.,
Anderson John L.
Publication year - 1977
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690230206
Subject(s) - membrane , porosity , mass transfer , materials science , boundary layer , diffusion , mass fraction , boundary (topology) , boundary layer thickness , layer (electronics) , composite material , chemistry , thermodynamics , chemical engineering , chromatography , mathematics , physics , mathematical analysis , biochemistry , engineering
Diffusional mass transfer across membranes with uniform but low pore densities was studied experimentally as a function of stirring rate and pore area fraction. The results were analyzed in terms of a stagnant film boundary‐layer model specially formulated for a heterogeneous membrane containing discrete pores. The overall membrane diffusional resistance is linearly related to the inverse of the pore area fraction of the membranes for a constant stirring rate. An equivalent boundary‐layer thickness can be defined which is independent of membrane properties but a unique function of stirrer speed. These experimental boundary‐layer thicknesses are greater by a factor of 3 than those predicted by a published Sherwood number correlation determined for homogeneous surfaces, but the stirring rate dependence is in excellent agreement with this same correlation.