Proposal and thermodynamic analysis of an ejection–compression refrigeration cycle driven by low-grade heat

Abstract

Ejection-compression refrigeration cycle reduces electricity consumption, by using huge quantity of low-grade heat, which increases equipment cost and occupies more space, especially when it is powered by solar heat. Hence, the large solar collector limits the practicability of ejection-compression refrigeration cycle. To solve this problem, a novel ejection-compression refrigeration cycle is proposed in this paper, which needs less heat and a smaller collector. It is theoretically compared to conventional vapor compression refrigeration cycle and conventional ejection-compression refrigeration cycle. It is also analyzed over wide temperature ranges. Results show that the proposed cycle has a COP 24% higher than conventional vapor compression cycle. The proposed cycle also has a COP 19% lower, heat transforming ratio 181% higher, and COPg 144% higher than those of conventional ejection-compression cycle. With a collector 5times smaller than a conventional ejection-compression cycle, the novel cycle is suitable for city buildings with limited space or economy sensitive users, although its COP is a little lower than conventional ejection-compression cycle. The effects of evaporating, condensing, generating, and intermediate temperatures (Te, Tc, Tg, and Tm) on cycle performance are explained. At Tm=10°C, the maximum COP of 4.78 is obtained with the optimized generation temperatures of 72°C.