Influence of the Position of an Internal Heat Exchanger on the Performance of a Dual-Evaporator Ejector Refrigeration System

Energy and exergy analyses were performed to assess the effect of the internal heat exchanger (IHX) position on the performance characteristics of a dual-evaporator refrigeration system using an ejector as an expansion device. Three positions were tested. The first one generates a superheating at the suction of the compressor, the second generates a superheating of the secondary fluid at the inlet of the ejector, and the third generates a superheating of the primary fluid at the inlet of the motive nozzle. The results of the simulation show that it is the second position that leads to the best increases in performance characteristics of the refrigeration system. With improvements in coefficient of performance (COP), volumetric cooling capacity, exergy efficiency, and refrigeration cooling capacity of 9.38%, 9.58%, 5.18%, and 19.12%, respectively, R1234yf is the best fluid. However, the use of IHX is not recommended for R717, especially in position 1. The results also show that the contribution of IHX to increasing system performance is greater the higher the degree of subcooling and the lower the IHX effectiveness. It was also noted that system performance increases with condensing and refrigeration temperatures and decreases with freezing temperature.