Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

This work provides accurate experimental (p, .rho., T) values for three binary mixtures of methane with helium: (0.95 (amount-of-substance fraction) CH4 + 0.05 He) and (0.90 CH4 + 0.10 He) at temperatures of (240, 250, and 260) K and (0.50 CH4 + 0.50 He) from (240 to 400) K. This work is a continuation of a previous one which reported accurate experimental (p, .rho., T) values for the (0.95 CH4 + 0.05 He) and the (0.90 CH4 + 0.10 He) binary mixtures over the temperature range from (250 to 400) K. All density measurements were performed by using a single-sinker densimeter with magnetic suspension coupling at pressures up to 20 MPa. Experimental values were compared with the corresponding densities calculated from the GERG-2008 and the AGA8-DC92 equations of state, respectively. Deviations from the GERG-2008 are much larger than from the AGA8-DC92 (up to -6.5%). These deviations increase with decreasing temperature, with increasing pressure, and with increasing helium fraction. In contrast, deviations from the AGA8-DC92 are within the 0.5% band. The experimental values were also used to calculate the second and the third virial coefficients, BoT; xP and CoT; xP, as well as the second interaction virial coefficient B12oTP for this mixture.