Measurement of the vapor–liquid equilibrium properties of the binary low GWP refrigerant R32/R1123

The vapor–liquid equilibrium properties of R32/R1123 binary refrigerant mixtures were precisely determined. Such mixtures have the potential to provide a reduced global warming potential although data regarding their properties is extremely limited, especially with regard to vapor–liquid equilibrium characteristics such as boiling point and dew point pressures, for which no actual experimental data exist. The present study acquired such data by means of two recirculation type apparatuses located at different universities. One apparatus, which was used to measure data in high temperature region, is installed at Toyama Prefectural University and includes an optical cell and two circulation loops with a thermostatted liquid bath. After thermal equilibration, a part of the sample in both loops is sandwiched between two valves and mixed with helium, following which the compositions are determined using gas chromatograpy. The other apparatus, which was for lower temperature region, at Kyushu University, has a similar design. The vapor–liquid equilibrium data were obtained between 300 and 330 K using the apparatus for high temperatures and from 273 to 313 K using the apparatus for low temperatures. These data were compared with predictions from the Helmholtz-type equation of state and a systematic deviation of approximately 1% was observed at low temperatures. A regression analysis using the binary interaction parameter k_ij for the modified Peng–Robinson equation of state more accurately reproduced the present measurement results.