Advanced exergy analysis of transcritical CO2 two-stage compressed air-source heat pump cycle

At present, the air-source heat pump with natural refrigerant CO2 has a very good application prospect. In order to tap its energy saving potential， the conventional exergy analysis method has been improved, and an advanced exergy analysis method has been adopted to further study the cycle of a transcritical CO2 two-stage compressed air-source heat pump. The results show that the proportion of the avoidable endogenous exergy loss of the system is 46.88%, which can be avoided by improving the system component performance. From the angle of advanced exergy analysis, the proportion of the low pressure compressor, the proportion of the high pressure compressor and the proportion of the expander have the highest optimization priority. The exergy loss of the proportion of the high pressure compressor accounts for 25.37% of the total exergy loss, and the optimization of the proportion of the high pressure compressor can significantly improve the system performance. The exergy loss of the evaporator is all caused by internal factors. The exogenous exergy loss and the proportion of the avoidable exergy loss of the throttle valve are negative, and the system performance can be improved by replacing other throttling equipment. There is an optimal high pressure corresponding to the highest exergy efficiency in the system. When the high pressure increases from 8 MPa to 10 MPa, the avoidable endogenous exergy loss of the proportion of the high pressure compressor increases by 1.96%.