Selection and validation on low-GWP refrigerants for a water-source heat pump

Heat pumps are generally recognized as an efficient energy-saving method, and are widely used in industrial and residential applications. Due to the ratification of the Kyoto Protocol, the use of high-GWP refrigerants is gradually being restricted and they will be phased out for heat pump systems. Currently, low-GWP refrigerants, such as R718, R1234ze(Z), R600, R600a, R1233zd(E) have been evaluated for high-temperature heat pumps. However, there is still a lack of choice and research regarding low-GWP refrigerants for conventional heat pumps. Therefore, taking the system's COP, volumetric heating capacity, pressure ratio and discharge temperature into consideration, R1234ze(E) is selected for study in this paper due to its relatively excellent system performance for wider working temperature ranges. Furthermore, a water-source heat pump using R1234ze(E) as the working fluid was simulated, built, and tested. The experimental results showed that the COP of the R1234ze(E) heat pump can reach 3.5 with a heat source varying from 10 degrees C to 30 degrees C and a water outlet temperature above 60 degrees C. The simulation results are in good agreement with experimental data. Moreover, the component characteristics were compared between R1234ze(E) and R134a. The results show that R1234ze(E) has apparent advantages for residential use and is economically comparable with R134a.