Abstract
Recovery of expansion work in vapor compression heat pump cycle has gained much attention as a means of improving COP of carbon dioxide heat pump. Instal1ation of a two-phase ejector is one of the most promising ways of recovering expansion work. This paper is aimed at clarifying the characteristics of COP of ejector-equipped vapor compression heat pump cycle. Firstly, the ejector efficiency is defined as an isentropic efficiency of the ejector, and then the COP is compared with the conventional cycle and the expander-equipped cycle, which is another expansion-work-recovering cycle. The effects of internal heat exchange and compressor efficiency on expansion-work recovering cycle is clarified. After that, optimum design of the ejector is shown based on one-dimensional calculation of the fluid flows in the ejector. The efficiency of the ejector shows optimum when the suction flow is choked if the efficiencies at convergent mixing cone and diffuser are unity respectively. Finally, the performance of part load operation is clarified based on the fluid analysis in the ejector
