Performance evolution on a dual-temperature CO2 transcritical refrigeration cycle with two cascade ejectors

This study proposes a modified dual-temperature CO2 transcritical refrigeration cycle, in which two cascade ejectors are applied to enhance the performance of a dual-temperature refrigeration system. The theoretical investigations with energetic and exergetic methods have been carried out, the results show that the dual-ejector cycle exhibits higher coefficient of performance (COP) and system exergy efficiency than that of the basic throttling refrigeration cycle and single ejector refrigeration cycle. In comparison with the single ejector refrigeration cycle at the given operation conditions, the proposed system improves the COP and exergy efficiency by 5.26-25.5% and 9.0-28.7%, and the pressure lift ratio of the two cascade ejectors could be improved by 6.0-12.2%. The largest exergy destruction of the proposed cycle occurs in the gas cooler, followed by the ejectors accounting for the 28.9% of the system exergy destruction rate. The performance characteristics of the double ejector cycle show its potential advantages in dual-temperature CO2 transcritical refrigeration systems.