Experimental speed of sound for trans-1-Chloro-3,3,3-trifluoroprop-1-ene (R1233zd(E)) and trans-1,1,1,4,4,4-Hexafluorobut-2-ene (R1336mzz(E)) in gaseous phase

Abstract

trans-1-Chloro-3,3,3-trifluoroprop-1-ene (R1233zd(E)) and trans-1,1,1,4,4,4-hexafluorobut-2-ene (R1336mzz(E)) have gained increasing momentum due to their low global warming potential (GWP) and good performance in heat pumps and organic Rankine cycle (ORC) systems. Accurate thermodynamic property data are required for industrial and commercial applications. Speed of sound data with high precision are vital to developing dedicated equations of state (EoS) and calculating other thermodynamic properties. In this work, we measured the speed of sound in the gas phase of R1233zd(E) and R1336mzz(E) by the fixed-path acoustic resonance method using a cylindrical resonator. The dimensions of the resonator are calibrated by Ar, Kr and He. The speeds of sound of R1233zd(E) were obtained at temperatures ranging from 313.15 to 363.15 K and pressures up to 550 kPa, and those of R1336mzz(E) were obtained in the temperature range from 298.15 to 363.15 K and the pressure up to 805 kPa. The combined expanded relative uncertainty (k = 2) of the sound of speed is 2.1 × 10−4 for R1233zd(E) and 1.5 × 10−4 for R1336mzz(E). The sound-speed data of R1233zd(E) agree with the EoS developed by Mondejar with an average relative deviation of −0.003%, which is the most accurate. The R1336mzz(E) data are the first set of published experimental sound-speed data. The ideal-gas heat capacity at constant pressure and the second acoustic virial coefficient were derived and compared to published data. The data measured and derived in this work can be used to establish the dedicated EoS of R1336mzz(E) for better prediction of thermodynamic properties.