Low Environment Temperature Two-stage Compression Direct Heatingair Source CO₂ Heat Pump Water Heater Study On System Operation Characteristics

With the social progress and development,people's demand for energy is increasing,and the air source heat pump has gradually entered people's vision.The north of Qinling area in our country,the winter outdoor low temperature can reach-20?,usually the conventional single stage compression air source heat pump has been unable to use demand.In northwest China,high temperature hot water is often needed to clean and transport oil vehicles and other engineering vehicles.In view of the above problems,this paper proposes a low ring temperaturetwo-stagecompressiondirectheat airsourceCO₂ heatpumpwaterheater.In order to further understand the two-stage compressed CO2 heat pump water heater,according to the actual situation in Northwest China and the operating conditions of the experimental equipment,set up a test bench,the application of experimental equipment in the future to know actual situation,choose the outdoor environment temperature,air cooler inlet water temperature,cooling water flow rate as the research variables,measured test bench system under different working condition of the heating,energy efficiency coefficient?COPh?,cooling unit,water temperature,compressor pressure ratio and other parameters.Based on the experimental data,the influence of these parameters on the system performance was analyzed to prepare for the development and optimization of two-stage compressed CO₂ heat pump waterheater.The results show that:?1?as measured by the system COPh and system heat,cooling water flow rate of 2L/min,cooling unit into the water temperature is 10?,the outdoor environment temperature,respectively-10?and 0?,10?,change the filling quantity of refrigerant system,determining the best experimental stations filling quantity is 3.2 kg.?2?refer to the nominal working conditions of CO₂ heat pump water heaters in GB/t23137-2008.Experimental measured outdoor environment temperature of 12?,cooling water temperature is 16?,cooling water flow rate of 1.5L/min,the air cooler outlet temperature is 75.2?,the system COPh of 3.73,system heat of 6.4 kW.?3?the cooling water flow rate of 2L/min,water cooling unit into the temperature for 13?,with the increase of outdoor environment temperature,COPh,system heat,cooling unit,water temperature,high pressure machine pressure higher than all.Outdoor environment temperature for-12?,the water temperature of the cooling unit up to 56.3?.?4?the outdoor environment to 12?,cooling water flow rate of 1.5L/min,with air cooler into the water temperature,the system of energy efficiency coefficient,system heat is reduced,cooling unit,water temperature,high pressure machine pressure higher than all.Cooling unit into the water temperature is 16?,boot after 510 s basically stable in water temperature 66.1?;Cooling unit into the water temperature of 22?,the boot after 520 s basically stable in water temperature of 70.4?.Water cooling unit into the temperature raised 6?,the cooling unit,water temperature increased 4.3?,improve the cooling unit into the water temperature can effectively increase the air cooler water temperature.?5?outdoor environment temperature-10?,cooling unit into the water temperature is 10?.With the increase of cooling water flow rate,system energy efficiency coefficient?COPh?and heat production capacity increase,and air cooler outlet temperature and high-pressure machine pressure ratio decrease.When the cooling water flow rate is reducedto1L/min,theaircoolerwatertemperatureis63.3?.