Energetic optimization and exergetic performance investigation of an ejector refrigeration system using HCFO-1233zd(E) as a refrigerant

Abstract

In this study, the performance of an ejector refrigeration system using HCFO-1233zd(E) as the working fluid is investigated and presented. A novel improved modeling approach that considers ejector loss coefficients as functions of the ejector pressure lift and area ratio has been used. The resulting mathematical model developed using the first and second laws of thermodynamics and gas dynamics is solved using Engineering Equation Solver. Different ejector geometries with area ratios of 6.44, 7.04, 7.51, 7.73, 8.28, 8.62, 9.13, 9.41 and 10.64 were used in this study. The evaporator temperatures were between 0 °C and 16 °C, the generator temperatures were between 75 °C and 120 °C and the condensing temperatures varied between 20 °C and 40 °C. For the range of parameters used, the optimal coefficient of performance (COP) is in the range 0.11 and 0.88 for evaporator temperatures between 4 °C and 16 °C. At the optimal working conditions, the COP improves with higher area ratios, lower condensing temperatures and requires increased generator temperatures. In the critical mode of operation, both the energetic and exegetic performance of the ejector are shown to decline as generator temperatures increase, evaporator temperatures reduce and as the area ratios decrease. Thermodynamic investigation using the exergy analysis method indicates that most of the exergetic losses come from the ejector (46–56%) followed by the condenser (18–29%), the generator (21–26%), the evaporator (0.8–3%), and the throttle valve (1–1.6%), with the pump having a very small contribution. Moreover, correlations for the optimal generator and optimal COP were derived and presented.