Viscosity of He–Ar and He–Kr Binary Gaseous Mixtures in the Temperature Range 25–720°C

Abstract

Measurements were made of the viscosity of helium, argon, krypton, and the mixture pairs helium–argon and helium–krypton to elevated temperature. The viscosity of the pure gases was measured to a temperature of about 850°C, whereas that of the mixtures was measured to 720°C. The instrument used was that of an oscillating‐disk type, and absolute measurements were obtained. The data on the pure gases showed good agreement with previous work on oscillating viscometers but did not agree well with the older capillary‐flow measurements. It is contended that the present results enjoy a higher confidence level. The pure‐gas results were used to find optimum force parameters for the interaction potential. It was found that argon and krypton are best represented by the conventional Lennard‐Jones (6–12) potential, but helium is best represented by a (6–9.5) potential model. Due to the extremely shallow depth of the potential well for helium, the present viscosity data are inadequate to yield meaningful values for the force parameters for it. Consequently, force parameters derived from measured binary diffusion coefficients were used to test proposed combination rules. The combination rules were found to be moderately successful. The viscosity data were then used to calculate diffusion coefficients of the mixtures. These values were in good agreement with reliable correlations referred to in the paper. The viscosity of the pure components as well as that of the mixtures was used to generate skeleton tables for thermal conductivity; the interpolation scheme for them is described in the paper. In cases when these values can be compared with direct measurements, the agreement is good.