Performance evaluation of a modified R290 dual-evaporator refrigeration cycle using two-phase ejector as expansion device

Abstract

This paper presents a modified dual-evaporator ejector expansion refrigeration cycle (MDEEC) in which a two-phase ejector is used as the expansion device to recover the expansion work. Based on constant-pressure mixing theory, a thermodynamic model is developed to investigate the effects of various parameters on the system performance. Also a comparative study of the modified cycle with a conventional one (CDVCC) and a previous ejector cycle (COSEC) is conducted in terms of energy and exergy analysis. The results show that COP of the modified cycle is improved by about 10% and the exergy destruction of expansion device is reduced by more than 90% compared with the COSEC. At the operating condition of Tc = 45 °C and Te2 = 5 °C, the COP and exergy efficiency of the MDEEC can reach 6.515 and 0.3184, respectively, which are 42.6% and 36.7% higher than those of the CDVCC. It is also revealed the performance improvements become more significant at higher condensing temperatures or lower evaporating temperatures. Finally, the effects of the ejector components efficiency and the performance under off-design conditions are discussed.