Development of The Liquid-Phase Speed of Sound Measurement System for Thermophysical Properties Evaluation of Low-GWP Refrigerants

Abstract

Under the worldwide situation of the shift to the next-generation refrigerants with low global warming potential (GWP), there is a demand to evaluate the fundamental thermophysical properties of low-GWP refrigerants, which is essential for their practical application. In this study, we developed a speed of sound measurement apparatus in the liquid phase using a commercially available ultrasonic-pulse sound velocity sensor. The apparatus was calibrated using pure water and R1336mzz(Z) (cis-1,1,1,4,4,4-hexafluoro-2-butene) as the reference standards for speed of sound, and R1234yf (2,3,3,3- tetrafluoropropene) was measured to confirm the soundness of the speed of sound measurement. As a result, it was confirmed that the speed of sound for R1234yf in the liquid phase agreed with the existing values within the claimed uncertainty. The relative standard uncertainty of the speed of sound measurement in the liquid phase was estimated to be 0.084 %. Using the developed liquid -phase speed of sound measurement apparatus, R1336mzz(E) (trans-1,1,1,4,4,4-hexafluoro-2-butene) and R13I1 (trifluoroiodomethane) were measured as the low-GWP refrigerants since their liquid-phase speed of sound have not been reported yet. The speed of sound data for R1336mzz(E) were obtained at 28 points in the temperature range from 283 K to 343 K and pressure range from 1 MPa to 7 MPa, and those for R13I1 were obtained at 28 points in the temperature range from 273 K to 333 K and pressure range from 1 MPa to 7 MPa. The obtained speed of sound data were compared with the calculated values from the existing equations of state for R1336mzz(E) and R13I1, and it was found that the present measurement data for R1336zz(E) and R13I1 were smaller by down to 9 % and 2.4 %, respectively.