Measurements of Gaseous PVTx Properties and Saturated Vapor Densities of Refrigerant Mixture R-125+R-143a

The experimental PVTx properties of a binary refrigerant mixture, R-125 (pentafluoroethane) + R-143a (1,1,1-trifluoroethane), have been measured for a composition of 50 mass % R-125 by a constant-mass method coupled with an expansion procedure in a range of temperatures from 305 to 400 K, pressures from 1.5 to 6.1 MPa, and densities from 92 to 300 kg . m–3. The experimental uncertainties of the present measurements are estimated to be within +7.2 mK in temperature, +3.0 kPa in pressure, +0.12 kg . m–3 in density, and +0.040 mass % in composition. The sample purities are 99.953 mass % for R-125 and 99.998 % for R-143a. Seven saturated vapor densities and dew point pressures of the R-125 + R-143a system were determined, on the basis of rather detailed PVTx properties measured in the vicinity of the saturation boundary as well as the thermodynamic behavior of isochores near saturation. The second and third virial coefficients for temperatures from 330 to 400 K were also determined.