Studv On The Performance Of Transcritical CO₂Heat Pump Water Heater System With Ejector

Due to the harmful effects of them on the environment, the synthetic refrigerants, such as CFCs and HCFCs, are being phased out. As one of the national refrigerants, CO2has been revived as a potential refrigerant due to its environmental-friendliness, non-toxicity, non-flammability, high volumetric refrigeration capacity and favorable heat transfer performance. But the high throttling loss of the transcritical CO2cycle restricts the cycle’s performance. So an ejector is added in the transcritical CO2cycle to recover some of the kinetic energy of the expansion process. The performance of an ejector is mainly influenced by its geometrical dimensions and operating conditions. Focusing on these concerns, further theoretical and experimental investigations were carried out in this paper to investigate the effects of the ejector mixing section diameters and operation conditions on the performance of the ejector and the transcritical CO2heat pump water heater system with ejector (TCHSE). The main researches are as follows:1. The transcritical CO2heat pump water heater system was improved and tested. The refrigeration charges of the transcritical CO2heat pump water heater system with ejector (TCHSE) and the conventional transcritical CO2heat pump water heater system (TCHS) were investigated.2. Theoretical and experimental investigations on TCHS were carried out. The effects of the hot water temperature on the performance of TCHS, isentropic efficiency of the compressor and the thermodynamical perfectness of the gas cooler were analyzed.3. The effect of the diameter of the mixing section on the ejector performance was analyzed theoretically based on gas dynamics.4. A constant-pressure mixing model for the ejector to perform the thermodynamic analysis of TCHSE was established. The effects of the operation conditions on the relative performance of the ejector and TCHSE were investigated.5. Experimental study on effects of the geometrical dimensions and operating conditions on the ejector and TCHSE was carried out. The effects of different diameter of the mixing section, different evaporation temperature and different hot water temperature on the performance of the ejector and TCHSE were investigated.