Summary
The viscous and slip flow terms of the Hanks-Weissberg and Petty-Puritch gas flow equations are compared. A Couette correction of 3π/8 x radius must be added to the capillary length in the viscous term of the latter equation. The slip flow terms in the two equations are equivalent to within ±10%. A modified method is presented for calculating the radius and number of short capillaries from gas flow measurements. The applicability of this method was confirmed by measurements of gas flow through artificial membranes containing short capillaries. Earlier published values for the number and radius of pit membrane pores are recalculated using the modified method. The possible effects of very close spacing of pores in a membrane are discussed and it is suggested that the Couette correction is probably still applicable in this case.
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This work was supported in part by a Research Grant from the Science Research Council.
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Petty, J.A. Laminar flow of fluids through short capillaries in conifer wood. Wood Science and Technology 8, 275–282 (1974). https://doi.org/10.1007/BF00351861
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DOI: https://doi.org/10.1007/BF00351861