Towards Reference Viscosities of Carbon Monoxide and Nitrogen at Low Density Using Measurements between 290K and 680K as well as Theoretically Calculated Viscosities

An all-quartz oscillating-disk viscometer of very high precision was used to determine the temperature dependence of the viscosities of carbon monoxide and nitrogen at low densities. The measurements were based on a single calibration at room temperature with a value theoretically calculated on the basis of an accurate ab initio pair potential for helium and the kinetic theory of dilute monatomic gases. The uncertainty of the experimental data is conservatively estimated to be ±0.15% at room temperature increasing to ±0.20% at the highest temperature of 682 K. The new data are compared with values recommended by the National Institute of Standards and Technology in the framework of its Standard Reference Data Program REFPROP as well as with experimental data from the literature. Whereas the REFPROP values for nitrogen can be considered as reference values, the new experimental data for carbon monoxide are up to 2% higher than the REFPROP values and should be taken into consideration for a new correlation. The temperature dependence of the viscosities calculated theoretically using ab initio intermolecular potential energy hypersurfaces for carbon monoxide and nitrogen and the kinetic theory of dilute molecular gases should be used for extrapolating the viscosity correlations of both gases to low and high temperatures. In addition, the viscosity ratio of carbon monoxide to nitrogen is investigated with the purpose to establish an improved correlation for carbon monoxide.