Advanced Exergy Analysis of an Ejector-expansion TRCC (Trans-critical CO2) Cascade Refrigeration System

This paper identifies the inefficiencies of a proposed energy conversion system to improve its performance. The conventional exergy analysis is unable to identify these inefficiencies because it does not consider the interactions among the system components. The advanced exergy analysis does this however. The main role of advanced exergy analysis is to provide engineers with additional useful information for improving the design and operation of energy conversion systems. The information is achieved by splitting the exergy destruction into endogenous/exogenous and unavoidable/avoidable parts. In the present paper both the conventional and advanced exergy analyses are employed. The splitting raises the accuracy of exergy analysis and facilitates the system improvement. The used method in this paper for splitting is thermodynamic cyclemethod which considers hybrid cycles in each of which only one of the component operates on the real condition and the rest operate under ideal condition. Advanced exergy analysis of ejector-expansion trans-critical CO2 cascade refrigeration system consisting of two refrigeration systems, is discussed. The results indicate that although the conventional exergy analysis shows the highest exergy destruction for the ejector, the advanced exergy analysis suggests improving the gas cooler performance first. The compressor, ejector and evaporator are in the next stages for improvement because of their maximum value of endogenous avoidable exergy destructions.