Gas Phase PVT Properties for the Difluoromethane + Pentafluoroethane (R-32 + 125) System

Abstract

We present new PVT measurements in the gas phase for difluoromethane (R-32) + pentafluoroethane (R-125) mixtures at 0.5001 (30.24 mass %) and 0.6977 (50.01 mass %) mole fractions of difluoromethane (R-32). The measurements were performed with a Burnett apparatus, and the expanded uncertainties of the measurements with a level of confidence of approximately 99% were estimated to be ±0.8 kPa for pressure, ±8 mK for temperature, ±0.15% for density, and ±0.1 mol % for composition. The PVT properties of pure R-32 and R-125, which were obtained from the reanalysis of earlier Burnett measurements for R-32 and R-125 at our laboratory, are also presented in this paper. A virial-type equation of state for the R-32 + 125 system has been developed on the basis of the present measurements and other experimental data; this equation reproduces the experimental data in the gas phase within ±0.3% in pressure.