Performance Study On Highly Efficient CO₂Heat Pump Water Heater

At present, the energy shortage and environmental pollution has become theobstacles of limiting human sustainable development. With the gradually increase ofpeople’s life quality, the study of using environmentally friendly refrigerant CO2on heatpump system has received more attention. Transcritical CO2heat pump water systemresearch becomes an important part of the heat pump industry.Transcritical CO2heat pump water heater system was set as the research object, andthe CO2, R134a, R1234yf’s physical parameters was obtained with the aid of the software.At the same time, the performance analysis program was developed based on VB, thefactors such as temperature, pressure, efficiency and degree of the superheat thatinfluence the heat pump system’s COP was analyzed. Exergy analysis model of the maincomponents in the heat pump system was established, and the related factors thatinfluence system’s exergy loss was analyzed. Finally, the distributed parameter analysismethod was used to make simulations of the tube type gas cooler’s heat transferperformance, and the cooling water inlet temperature and mass flow of the CO2thatinfluences the heat transfer performance was studied.Studies have shown that transcritical CO2cycle with expander has the highest COP,regenerator times; the throttling valve is the worst. Among them, the two stagetranscritical CO2cycle with expander’s COP can be as high as6.589. In the transcriticalCO2cycle with throttling valve and regenerator, exergy loss mainly exists in throttlingvalve and compressor. In the transcritical CO2cycle with expander, the expander’sexergy loss achieves the minimum level. When the cooling water inlet and outlet remainsa certain temperature, the heat exchange amount increases with the mass flow. Theresults provide theoretical basis for optimizing design of the related components anddeveloping heat pump products.