Approximate Formulas for the Viscosity and Thermal Conductivity of Gas Mixtures. II

Abstract

Approximate expressions for the viscosity and thermal conductivity of monatomic gas mixtures have been derived from the rigorous kinetic theory formulas for binary mixtures. The approximations, which are of the Sutherland—Wassiljewa form, are compared with rigorous calculations for binary and ternary mixtures of the noble gases. These approximations are very accurate: maximum errors are three parts in ten thousand for viscosity (He–Ne–Ar at 20°C) and seven parts in ten thousand for thermal conductivity (He–Kr–Xe at 29°C); the corresponding root-mean-square errors for all the calculations are 0.015% for viscosity and 0.036% for thermal conductivity. Thus, these approximations seem adequate for all practical applications; indeed, if greater accuracy is required, the higher Chapman—Enskog approximations should be considered as well.