Utilization of CO2 and R1234ze(E) as refrigerant: determination of mixture volumetric properties at the vicinity of critical point.

In recent years, binary and multi-mixture refrigerant have been developed to increase the cycle efficiency and reduce environmental effects. The most promising mixture are composed of R1234yf or R1234ze(E) with HFC or natural refrigerants. However, the experimental data of new mixture is still in short. In this work, we present the results obtained for the temperature-density diagram of CO2 and R1234ze(E) at the vicinity of the mixture critical point for 4 different compositions. Measurements were done by an equipment whom technique is based on synthetic visual method with observation of disappearance of liquid-vapor interface. Cubic equation of state and Refprop model were used to correlate the data. With cubic EoS, the critical point is determined by considering Heidemann et Michelsen method. The results obtained show a good agreement between experiments and proposed modelling.