Thermodynamic Modeling of Gas-Phase PVTx Properties for the Ternary R-32/125/143a System

Experimental PVTx property data have been used to develop a thermodynamic model of the gas-phase PVTx properties for R-32/125/143a in terms of a truncated virial equation of state.It is developed on the basis of the experimental PVTx property data which were obtained by a group of the present authors. The present model represents the input data with a high reproducibility, i.e., within ±0.2% in pressure for each pure component, ±0.25% for binary mixtures except for R-32/143a, and ±0.3% for ternary mixtures. The present model covers a temperature range of 300 to 380 K, pressures up to 4.5 MPa, and densities up to 2.5 mol·dm−3 at any composition of the present ternary system.The uncertainty of the present model is considered being within ±0.3% in pressure and ±0.3% in the second virial coefficient. The thermodynamic behaviors of the specific isobaric heat capacity, isochoric heat capacity, and speed of sound are also discussed, in addition to the examination of the temperature dependence of the second and third virial coefficients.