Investigation of improvement potential of a double-efficient CO2 cooling and heating system using an ejector with advanced exergy analysis

Abstract

This paper presents an improvement potential investigation of a double-efficient CO2 cooling and heating system using an ejector, which can operate in cooling or heating mode. For the first time, advanced exergy analysis is employed to offer improvement direction and guidance for the practical application of this novel system. Compared to the conventional exergy analysis, which is widely used in previous work, advanced exergy analysis can supply more information about the interaction among components and the avoidable exergy destruction under the technical constrains. Thus, more practical and accurate conclusions can be drawn. The results reveal that 74.56 % of the total exergy destruction is endogenous in cooling mode, demonstrating the weak interaction among components. The compressor should be given the highest priority for improvement, due to its largest sum of avoidable exergy destruction (17.71 W). The effect of ejector component efficiency is also discussed. As it varies from 0.5 to 0.9, the system exergy efficiency rises from 11.59 % to 14.18 %. Furthermore, the proposed system shows great advantage with 31.31 % less exergy destruction compared to ejector expansion refrigeration cycle. In heating mode, the compressor also deserves to be optimized first. But the expansion valve possesses no effort for improvement due to its negative sum of avoidable exergy destruction (−1.203 W).