Permeametry: correction for gas expansion as it flows through a bed of powder

Abstract

In the 1982 revised version of BS 4359: Part 2, Air Permeametry Methods, the one-term Carman-Kozeny equation has been replaced by the two-term Carman-Arnell equation. The latter equation comprises the former together with a slip-flow term which contains an unknown variable (δk 0 /k) for which the value 0.45 has been adopted. The variable can be evaluated using a constant-flow permeameter and an equation modified for the expansion of the gas as it flows through the bed of powder. Although the theoretical treatment is simple, the required apparatus is complex. The converse applies to the alternative variable-flow permeameter. It was noted that the proposed equation in the draft British Standard was incorrect and a correct equation has been developed.