Thermal Conductivity Measurements for trans-1,3,3,3-Tetrafluoropropene (R1234ze(E)) in Liquid Phase

Refrigeration, heat pumps and air conditioning sectors are under pressure to find low GWP working fluids suitable for the substitution of the current high GWP refrigerants, as required by the European Regulation EU No 517/2014. Halogenated olefins (HFOs and HCFOs) are the most promising group of synthetic compounds being considered for such purpose, due to their very low GWP values, similar to those of natural refrigerants. Trans-1,3,3,3- tetrafluoropropene (R1234ze(E)) belongs to this group. As several HFOs, R1234ze(E) is mildly flammable (A2 on the base of the ASHRAE classification). Having a normal boiling point of 254.15 K, it is a potential alternative refrigerant to R134a for medium temperature applications such as air-cooled and water-cooled chillers, heat pumps, refrigerators, vending machines and CO2 cascade systems. Here, thermal conductivity measurements performed by means of a new transient hot-wire (THW) instrument are proposed for the liquid phase. The THW instrument is endowed with a two Ta wires (diameter 25 ?m) sensor. The measurements were performed at isothermal conditions in the range of temperatures between 243 K and 343 K, with pressures up to 8 MPa. The estimated standard uncertainty is lower than 2%. The results have been compared with the data available in the open literature.