Theoretical and experimental study on pumping characteristics of low-GWP refrigerants in solar ejector cooling system

Abstract This study evaluates two low-global warming potential (low-GWP) refrigerants—R1233zd(E) and R1234ze(Z)—for use in solar ejector refrigeration systems. A steady-state thermodynamic model is developed to compare their performance with baseline R134a across representative operating conditions. Key metrics include refrigerant pump power, system coefficient of performance (COP), and energy efficiency ratio (EER). At a 10 kW cooling load, pump energy demand drops by 73.2% and 68.2% for R1233zd(E) and R1234ze(Z), yielding EER values of 27.11 and 22.64—over four times that of R134a. Though COPs (0.19 and 0.20) are modestly lower than R134a (0.25), markedly reduced saturation pressures translate to improved electrical efficiency and safer operating envelopes.To validate pumping feasibility under low-pressure refrigerant conditions representative of these fluids, a closed-loop multistage centrifugal pump test platform was constructed. Variable-frequency trials confirmed stable subcooled liquid delivery and identified a peak measured overall pump efficiency near 30%, consistent with model expectations. The combined simulation–experiment evidence indicates that R1233zd(E) and R1234ze(Z) are strong candidates for small- to medium-scale solar ejector cooling in low-carbon buildings.