HYDRODYNAMIC THEORY OF MULTICOMPONENT DIFFUSION AND THERMAL-DIFFUSIONIN MULTITEMPERATURE GAS-MIXTURES

A phenomenological theory is developed for multicomponent diffusion, i ncluding thermal diffusion, in gas mixtures in which the components ma y have different temperatures. The theory is based on the hydrodynamic approach of Maxwell and Stefan, as extended and elaborated by Furry [ 1] and Williams [2]. The present development further extends these ear lier treatments to multiple temperatures and multicomponent thermal di ffusion. The resulting diffusion fluxes obey generalized Stefan-Maxwel l relations which include the effects of ordinary, forced, pressure, a nd thermal diffusion. When thermal diffusion is neglected, these relat ions have the same form as the usual single-temperature ones, except t hat mole fractions are replaced by pressure fractions (i. e., ratios o f partial pressures to total pressure). The binary and thermal diffusi on coefficients are given in terms of collision integrals. Single-temp erature systems and binary systems are treated as special cases of the general theory. A self-consistent effective binary diffusion approxim ation for multitemperature systems is presented.