Comparative performance analysis of a self-heat recuperation driven ejector subcooling transcritical CO₂ refrigeration systems using different throttling devices.

Transcritical CO2 refrigeration system is a crucial technology with great application potential in refrigeration and heat pump areas. However, it faces the challenge of low energy efficiency due to large throttling loss. To improve the system performance, the large amount of waste heat discharged from the compressor in the transcritical CO2 refrigeration cycles can be utilized to drive the ejector refrigeration cycle to subcooling the outlet CO2 of gas cooler. A self-heat recuperation driven ejector subcooling transcritical CO2 refrigeration systems using throttling valve (TVHRS),expander (EXPHRS) and ejector (EJEHRS) as throttling devices are proposed. The energy and exergy models are established, and parametric comparison analysis are conducted on the proposed systems and the baseline cycles. Results show that the cycles with heat recovery have a large improvement both in COP and exergy efficiency ηex compared to their base cycles. Within the ambient temperature of 35 ~ 45 ◦C, the COP of TVHRS, EXPHRS, and EJEHRS is enhanced by 12.5 % ~ 19.8 %, 6.3 % ~ 9.6 %, and 5.8 % ~ 9.6 %, and the ηex improved by 11.6 % ~ 20 %, 13.0 % ~ 19.1 %, and 5.3 % ~ 9.5 %, respectively. The self-heat recuperation driven ejector subcooling transcritical CO2 refrigeration systems have a large potential for application.