Experimental investigation on the effect of expansion valves in a dual evaporator ejector refrigeration system using R134a and R456a

Abstract

ABSTRACT The purpose of this study was to experimentally investigate a dual evaporator ejector system (DEES) operating with R134a and R456a. In order to see the effect of expansion valves in the system, the experimental setup was arranged in two different configurations. In the first configuration, DEES was operated with dual thermostatic expansion valves (DEES-DTXV). In the second configuration, DEES was operated with a single thermostatic expansion valve (DEES-STXV). In both configurations, the system was tested with R134a and R456a. The effective performance values of the system were investigated based on the entrainment ratios (ERs). It was found that DEES-STXV outperformed DEES-DTXV in terms of total cooling capacity and coefficient of performance. When the system was operated as DEES-STXV, the total cooling capacity obtained from R134a was 14% higher than that obtained from R456a at the ER value of 0.5. In addition, it was found that the ERs had a significant effect on the cooling capacities; therefore, it is not recommended to operate the DEES at the ERs greater than 0.8 in both configurations. Moreover, DEES-DTXV was found to be superior to DEES-STXV in that very low evaporation temperatures could be achieved in the secondary evaporator in DEES-DTXV. Finally, it was found that the performance values of R456a were close to those of R134a; so, R456a can be used as an alternative refrigerant in dual evaporator refrigeration systems with ejector.