New concepts in molecular gas flow

This paper will outline several new concepts dealing with molecular flow calculations. One is a simple equation for calculating the ‘‘Clausing’’ transmission probability through circular tubes. A technique will also be demonstrated for developing similar expressions for the short-tube probability of other tube cross sections. Tube conductance will then be compared to transmission probabilities in terms of exit losses, entrance losses, and changes from random gas flow to fully developed tube flow. A format will be presented which assists in converting between short-tube conductance and probabilities. Finally, a correction term is added to Oatley’s probability combining equation to compensate for ‘‘beaming’’ effects. This term reduces the normal maximum error for circular tube calculations from 3.7% to 0.28%.