SIMPLER FORMULAE FOR THE THERMAL DIFFUSION FACTOR OF BINARY GAS MIXTURES

Abstract

Simpler formulae for the second approximation to the thermal diffusion factor of a binary gas mixture are derived according to both the approximation procedures of Chapman and Cowling, and Kihara. These formulae are much simpler than the rigorous theoretical formulae from the view point of computational labor. These new formulae are derived by expanding the rigorous expressions in powers of the molecular weight ratio, M, and deleting all those terms which contain explicitly the power of M higher than two. The accuracies of these simpler formulae are demonstrated by numerical calculations on gas systems as a function of both temperature as well as composition.