Wide-Ranging Reference Correlations for Dilute Gas Transport Properties Based onAb InitioCalculations and Viscosity Ratio Measurements

Abstract

Combined use of experimental viscosity ratios together with ab initio calculations for helium have driven significant improvements in the description of dilute gas transport properties. Here we first use improvements made to ab initio helium calculations to update viscosity ratios measured for H2, Ar, CH4, and Xe by May et al. in 2007 over the temperature range (200 to 400) K, reducing the uncertainties of the data to 0.055%, 0.038%, 0.067%, and 0.084%, respectively. Separately, we extend the technique of combining viscosity ratios with ab initio calculations to develop new reference correlations for the dilute gas viscosity of 10 gases: helium, neon, argon, krypton, xenon, hydrogen, nitrogen, methane, ethane, and propane. This is achieved by combining the ratios of viscosities calculated ab initio at the target temperature and at 298.15 K with experimentally-based reference viscosity values for each gas at 298.15 K. The new reference dilute gas viscosity correlations span temperature ranges from at least (150 to 1200) K, with relative uncertainties between 30% (krypton) to 85% (methane) lower than the original ab initio results. For the noble gases, ab initio calculations for the Prandtl number are used to develop reference correlations for thermal conductivity ranging from at least (100 to 5000) K, with relative uncertainties ranging from 0.04% (argon) to 0.20% (xenon). The new reference correlations are compared with available experimental data at dilute gas conditions. In general, the data agree with the new correlations within the claimed experimental uncertainty.