Heat Conductivity of Polyatomic and Polar Gases

Abstract

The formal kinetic theory of Wang Chang and Uhlenbeck and of Taxman has been used to derive explicit expressions for the heat conductivity of polyatomic and polar gases. By systematic inclusion of terms involving inelastic collisions the usual modified Eucken expression is derived as a first approximation, and as a second approximation an expression involving the relaxation times for various internal degrees of freedom (as well as the viscosity, diffusion coefficients, and heat capacity). For polar gases a second effect is often important in that a resonant exchange of rotational energy is possible. The comparison of experimental results with those calculated using empirical values of relaxation times is generally satisfactory, and most of the previously noted anomalies in the ratio f=λM/ηCv are accounted for quantitatively.