Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

A vibrating wire instrument, in which the wire was clamped at both ends, was used to measure the viscosity of {xCO2 + (1 x)CH4} with x = 0.5174 with a combined uncertainty of 0.24 lPa s (a relative uncertainty of about 0.8 %) at temperatures T between (229 and 348) K and pressures p from (1 to 32) MPa. The corresponding mass density q, estimated with the GERG-2008 equation of state, varied from (20 to 600) kg m 3. The measured viscosities were consistent within combined uncertainties with data obtained previously for this system using entirely different experimental techniques. The new data were compared with three corresponding states-type models frequently used for predicting mixture viscosities: the Extended Corresponding States (ECS) model implemented in REFPROP 9.1; the SUPERTRAPP model implemented in MultiFlash 4.4; and a corresponding states model derived from molecular dynamics simulations of Lennard Jones fluids. The measured viscosities deviated systematically from the predictions of both the ECS and SUPERTRAPP models with a maximum relative deviations of 11 % at (229 K, 600 kg m 3) and 16 % at (258 K, 470 kg m 3), respectively. In contrast, the molecular dynamics based corresponding states model, which is predictive for mixtures in that it does not contain any binary interaction parameters, reproduced the density and temperature dependence of the measured viscosities well, with relative deviations of less than 4.2 %.