The gaseous sound speed and density measurements for R1132(E) and its binary mixture with R1234yf.

Next-generation refrigerants with low global warming potential (GWP) are required for sustainable refrigeration and air-conditioning systems. R1132(E), trans-1,2-difluoroethylene, is one of hydrofluoroolefins (HFOs) with low GWP, expected to be used in residential and industrial air-conditioning systems. The authors measured the gaseous sound speed of R1132(E) and its binary mixture with R1234yf by employing the acoustic resonance technique using a cylindrical cavity. The sound speed data were obtained from the measurement of acoustic resonance frequencies in the cavity filled with a sample gas. The cavity dimension was determined by measuring electromagnetic resonance frequencies at the same temperature under vacuum. The electromagnetic resonance frequencies in the sample gas filled cavity were also measured to obtain the gaseous dielectric permittivity, which leads to the density in accordance with the Clausius-Mossotti relation. The obtained thermodynamic properties would contribute to developing the fundamental equations of state and the mixture models.