Measurement of gaseous speed of sound for R1234ze(E) and R1234ze(E)+ R1336mzz(E) binary mixture using a cylindrical resonator.

Trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) and trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)), along with their mixtures, represent a new generation of low-global-warming-potential working fluids with significant promise. This study aimed to measure the gaseous speed of sound using Cylindrical Fixed-Path Interferometry. The core component, the cylindrical resonator, had its length and radius precisely calibrated using argon. Combining the calibrated dimensions with the measured resonance frequency, we determined the speed of sound of R1234ze(E) in the temperature range of 313.15 K~363.15 K and the pressure range of 50 kPa~1030 kPa with a relative extended uncertainty (k = 2) of 0.029 %. Our comparison with the available speed of sound data revealed that the multiparameter equation of state for R1234ze(E) exhibits a systematic positive bias in the pressure range of 0~1000 kPa for speed of sound calculation. From the measured speed of sound of R1234ze(E), we calculated its ideal-gas heat capacity and acoustic second virial coefficients. These coefficients were subsequently regressed to obtain molecular parameters for the hard-core square-well molecular potential model, enabling the derivation of the density second virial coefficients. Furthermore, the speed of sound of R1234ze(E)+ R1336mzz(E) binary mixture was measured in the temperature range of 313.15 K~363.15 K and the pressure range of 59 kPa~800 kPa with a relative extended uncertainty (k = 2) of 0.064 %. By integrating the mixture speed of sound with the pure component properties, we determined the acoustic second virial coefficients of R1234ze(E)+R1336mzz(E). These results provide essential data support for developing a specialized thermodynamic model for the mixture.