Reference Viscosities of H2, CH4, Ar and Xe at Low Densities
E May, Robert F. Berg, Michael R. Moldover
We determined the zero-density viscosity eta of hydrogen, methane and argon in the temperature range 200 K to 400 K, with standard uncertainties of 0.084 % for hydrogen and argon and 0.096 % for methane. These uncertainties are dominated by the uncertainty of helium s viscosity eta(He), which we estimate to be 0.080 % from the difference between ab initio and measured values at 298.15 K. For xenon, our measurements ranged between 200 K and 300 K and we determined eta(Xe) with an uncertainty of 0.11 %. The data imply that xenon s viscosity virial coefficient is positive over this temperature range, in contrast with the predictions of corresponding states models. Furthermore, the xenon data are inconsistent with Curtiss prediction that bound pairs cause an anomalous viscosity decrease at low reduced temperatures. At 298.15 K, we determined the ratios eta(Ar)/eta(He), eta(CH4)/eta(He), eta(H2)/eta(He), eta(Xe)/eta(He), eta(N2)/eta(He), and eta(C2H6)/eta(He) with a relative uncertainty of less than 0.024 % by measuring the flow rate of these gases through a quartz capillary while simultaneously measuring the pressures at the ends of the capillary. Between 200 K and 400 K, we used a two-capillary viscometer to determine eta(gas)/eta(He) with an uncertainty of 0.024 % for H2 and Ar, 0.053 % for CH4, and 0.077 % for Xe. From eta(gas)/eta(He), we computed eta(gas) using the values of eta(He) calculated ab initio. Finally, we computed the thermal conductivity of Xe and Ar from eta(gas) and values of the Prandtl number computed from interatomic potentials. These results may help improve correlations for the transport properties of these gases and assist efforts to develop ab initio two- and three-body intermolecular potentials for these gases.
, Berg, R.
and Moldover, M.
Reference Viscosities of H<sub>2</sub>, CH<sub>4</sub>, Ar and Xe at Low Densities, International Journal of Thermophysics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=830996
(Accessed June 4, 2023)