Performance analysis of CO2 heat pump systems with ejectors based on pinch point

In order to study the transcritical CO2internal subcooling heat pump system with an ejector (TCISE), a thermodynamic model of TCISE is established based on the pinch point, and the effects of the inlet and outlet temperatures and flow rate of cooling water on system performance are analysed. The results show that when the inlet temperature of cooling water decreases from 25 ℃ to 15 ℃, the optimal high pressure drops from 9.3 MPa to 8.8 MPa, which decreases by 5.4%, and the maximum COP increases from 3.83 to 4.27, which increases by 11.49%.There are critical cooling water outlet temperature and critical cooling water mass flow rate in TCISE.When the inlet temperature of cooling water is constant and the outlet temperature is lower than the critical outlet temperature or the mass flow rate is higher than the critical mass flow rate, the COP of the system remains unchanged.