Viscosity of {xCH4 + (1 – x)C3H8} with x = 0.949 for Temperatures between (200 and 423) K and Pressures between (10 and 31) MPa

The viscosity of { x CH 4 + (1 – x )C 3 H 8 } with x = 0.949 was measured at temperatures between (200 and 423) K and pressures in the range (10 to 31) MPa using a vibrating-wire-viscometer with the wire clamped at both ends and operating in steady-state mode. Over these conditions the fluid mass density, which was calculated from the measured temperature and pressure using the GERG-2008 equation of state, ranged from (120 to 360) kg·m –3 . A three-parameter polynomial in density was able to represent the measured viscosities, which ranged between (19 and 53) μPa·s, with an r.m.s. deviation of 0.47 μPa·s. This was comparable to the average combined uncertainty of the measurements (0.43 μPa·s), and no temperature dependence of the viscosity was resolvable within the experimental uncertainty beyond that incorporated within the density obtained from the equation of state. The viscosity of CH 4 + C 3 H 8 reported herein along with measurements previously reported in the archival literature at densities up to 500 kg·m –3 have been compared with estimates obtained using two corresponding states-type models, which were implemented in the software packages REFPROP and MultiFlash, respectively. The predictions of both models were similar at densities below 200 kg·m –3, with the extended corresponding states model (ECS) implemented in REFPROP performing better than the SUPERTRAPP model implemented in MultiFlash at higher densities. The relative deviations of the measured viscosities from the ECS REFPROP predictions range from −5 % around 150 kg·m –3, which is in the vicinity of methane’s critical density, to about +2 %, at the highest densities, whereas the relative deviations from SUPERTRAPP MultiFlash range from +1 % around 150 kg·m –3 to −12 % at the highest densities measured. The trend relative to ECS REFPROP is consistent with those found for literature viscosities measured for mixtures with x > 0.75.