Analysis of an ejector vapour compression cycle for household refrigerator.

There are several ways of improving the performance of a vapour compression refrigeration cycle and using an ejector as expansion device is one of the possibilities. As a matter of fact, the ejector can reduce throttling losses in refrigeration systems. In this paper a comparison between a real vapour compression cycle for a household refrigerator and ejector vapour compression cycles is performed by simulation in order to evaluate the performance enhancement that can be obtained. The analysis of the ejector cycle, considering both a constant area and a constant pressure device, is presented by varying the schematic of the system and performance parameters. The best performing cycle is a constant pressure ejector cycle without any suction liquid heat exchanger: it can allow improvements over the standard reference cycle whenever the primary nozzle efficiency is above 50% and diffuser efficiency above 60%. When all the nozzles efficiency are set to 85%, the COP improvement achievable is about 9%.