Thermodynamic Property Measurements of Binary Refrigerant Blends R1132(E)/R1234yf
摘要
PVTx properties, saturated densities, critical parameters, and vapor–liquid equilibria (VLE) of hydrofluoroolefin (HFO) binary refrigerant blends of R1132(E)/R1234yf were comprehensively measured. The PVTx properties over the vapor, liquid, and supercritical phases were obtained by the isochoric method in the temperature range from 300 K to 410 K, at pressures up to 6.9 MPa, and at densities between 51 kg·m−3 and 925 kg·m−3 for R1132(E)/R1234yf blends with mass fractions of (0.23/0.77), (0.30/0.70), (0.50/0.50), and (0.70/0.30). The saturated densities of R1132(E)/R1234yf blends with mass fractions of (0.30/0.70), (0.50/0.50), and (0.70/0.30) were measured by the visual observation of the meniscus disappearance and also determined from the inflection points of the PVTx isochore lines in the temperature range from 305 K to 352 K and at densities between 51 kg·m−3 and 925 kg·m−3. The saturated densities obtained using the two methods were consistent with each other. Based on the saturated densities, the critical parameters of these three blends were determined by the consideration of the meniscus disappearing level as well as the intensity of the critical opalescence. Furthermore, the critical locus correlations depending on the surface fractions were formulated. The VLE of the R1132(E)/R1234yf blends were measured from 263 K to 323 K based on the recirculation method, and a mixing parameter of a simple cubic EOS was determined fitting to the VLE data. The PVTx property, saturated density, critical parameter, and VLE data were compared with a preliminary Helmholtz energy equation of state (EOS) for the blends, and systematic deviations were observed between the EOS and the experimental data, showing absolute average deviations of the PVTx property data ranging from 0.88 % to 1.2 % in density depending on the compositions except for the near-critical densities.