Thermodynamics Analysis of the Transcritical CO2 Heat Pump for Heating Applications

An experimental transcritical CO
2
heat pump system was implemented in Harbin, China to conduct the system thermodynamic analysis. The effects of regenerator efficiency, high pressure, low pressure, and outlet temperature of the gas cooler on COP and heating load were investigated. Furthermore, the sensitivity analysis was applied to ensure the sensitivity degrees of the parameters on COP and heating load. The results show that when the regenerator efficiency increased from 0 to 0.8, COP increased from 2.7 to 3.3 and the heating load changed from 14.7 kW to 22.6 kW. COP was maximum (4.1) at the high pressure of 10.0 MPa, and the heating load increased from 20.0 kW to 36.6 kW as the high pressure climbed from 8.5 MPa to 11.0 MPa. When the low pressure increased from 4.5 MPa to 7.0 MPa, COP increased from 4.1 to 8.0 and the heating load decreased from 33.6 kW to 22.0 kW. When the outlet temperature of the gas cooler increased from 30 °C to 55 °C, COP decreased from 5.8 to 2.3 and the heating load decreased from 36.6 kW to 16.9 kW. The improvements of COP and heating load should preferentially increase the high pressure due to its maximum average sensitive degree of 0.192 on the COP and 4.328 on the heating load.