Experimental and numerical study on transcritical CO2 air source heat pump water heater

As environmental problems become more and more serious, CO2 2 is widely used as a natural work material in heat pump water heaters. In order to better improve the performance of CO2 2 air-source heat pump water heater, a trans-critical CO2 2 quasi-two-stage compression heat pump system with ejector (TCIEJ) is proposed. And a transcritical CO2 2 air-source heat pump water heater experimental bench was built. The effects of parameters such as cooling water flow rate, high pressure and compressor frequency on the performance of the heat pump were tested. A simulation model of TCIEJ was also developed to simulate the system performance. The results show that when the cooling water flow rate is increased from 70 kg/h to 122.5 kg/h the COP is improved by 30 %, while the cooling water discharge temperature is reduced by 15.4 %. System performance can be enhanced by increasing the cooling water flow rate within the temperature range required to meet hot water demand. When the high-pressure pressure of the TCIEJ system was increased from 8.0 MPa to 10.4 MPa, the cooling water discharge temperature increased by 17.66 degrees C on average. Even in the ambient temperature of 0 degrees C high-pressure pressure of 10.4 MPa, the compressor discharge temperature is only 85.77 degrees C. It shows that the combination of make-up air technology and ejectors effectively reduces the compressor discharge temperature, which is conducive to improving the compressor's service life.