Speed of sound measurement of R1132(E) in the liquid phase using an ultrasonic-pulse sensor.

Under the Kigali Amendment to the Montreal Protocol, next-generation refrigerants with low global warming potential (GWP) are increasingly required in the air-conditioning and refrigeration sectors. The speed of sound in the liquid phase is an important thermodynamic property for developing the fundamental equations of state for refrigerants. In this study, the authors developed an apparatus to measure the liquid-phase speed of sound using a commercially available ultrasonic-pulse sensor. The sensor was calibrated using pure water and R1336mzz(Z) as reference fluids with distinct speed of sound values. R1234yf and R32 were measured to validate the speed of sound measurement, and the results showed good agreement with previously reported data within the estimated measurement uncertainty of 0.17 %. Furthermore, the apparatus was applied to measure the speed of sound in R1132(E), a hydrofluoroolefin (HFO), over a temperature range of 263 K to 343 K and at pressures up to 7 MPa.