Experimental investigation of a two-phase ejector cycle suitable for use with low-pressure refrigerants R134a and R1234yf

• Alternate two-phase ejector cycle with two evaporation temperatures was investigated experimentally.
• Alternate ejector cycle offers advantages over standard two-phase ejector cycle.
• COP improvements of up to 6% with R1234yf and 5% with R134a compared to a realistic baseline were achieved.

This paper presents the results of an experimental investigation in which the performance of the low-pressure fluids R134a and R1234yf was compared between a two-phase ejector cycle and expansion valve cycles. An alternate two-phase ejector cycle, in which the pressure lift provided by the ejector was utilized in order to provide multiple evaporation temperatures, was constructed and tested. The experimental results show that ejectors designed for low-pressure fluids were able to achieve similar but lower work recovery efficiencies compared to CO2 ejectors. When compared to a two evaporation temperature expansion valve cycle, the ejector cycle showed maximum COP improvements of 12% with R1234yf and 8% with R134a. When compared to a single evaporation temperature expansion valve cycle, the ejector cycle showed maximum COP improvements of 6% with R1234yf and 5% with R134a. The effect of evaporator design on ejector cycle COP improvement was also demonstrated experimentally.