Transport properties in dilute gases: an approach using time-correlation functions. Part 2.—Viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant

Abstract

The method of time-correlation functions, using the first collision approximation described in Part 1, is used to derive formulae for the viscosity and thermal conductivity of gases and gas mixtures in which the exchange of molecular internal energy is significant. For the viscosity of single gases the formulae of Wang Chang and Uhlenbeck are obtained but for other systems new approximate formulae are derived which are simpler than those of Wang Chang and Uhlenbeck. Some of the approximations used by Mason and Monchick are used to simplify these expressions further. The equations are used to suggest a method of calculating the thermal conductivities of mixtures of gases, in which internal translational relaxation is occurring, using data from binary mixtures. Finally, it is shown how the approximate equations of this paper can be obtained by making approximations to the rigorous kinetic theory.