Conventional and advanced exergy analyses of transcritical CO2 ejector refrigeration system equipped with thermoelectric subcooler

Abstract

This paper assesses the exergetic performance inside transcritical CO2 ejector refrigeration system integrated with thermoelectric subcooler (EJE + TES) through conventional and advanced exergy analyses. The results point out that 89.44% of the total exergy destruction is endogenous, which clearly demonstrates that it is not close in the interrelations among the system components. In addition, increasing the efficiency of the different components can decrease the exergy destruction by about 53.36%. The avoidable exergy destructions induced by the compressor is the highest, which indicates that priority should be given to the improvement of the compressor, followed by the thermoelectric subcooler, evaporator, ejector and gas cooler, while the expansion valve has almost no potential for improvement. This conclusion differs from that obtained by the conventional exergy method. The effects of the pinch temperature difference in each heat exchanger, as well as the compressor and ejector efficiencies on cycle theoretically exergetic performance are considered. When the compressor and ejector efficiencies increase from 0.5 to 0.9, the avoidable endogenous exergy destruction taking place in the corresponding system component are reduced by 93.61% and 82.33%, respectively. The performance of the EJE + TES system can be enhanced through reducing the pinch temperature difference.

Keywords

• Advanced exergy analysis
• Transcritical refrigeration system
• CO2
• Ejector
• Thermoelectric subcooler