| In recent years,people pay more and more attention to the quality of life and health.At present,people are facing the most serious problems,such as energy waste and environmental pollution.Traditional air conditioning systems cause a lot of energy waste,so air source heat pump system came into being,among which carbon dioxide heat pump system is the most environmentally friendly and energy-saving.The circulating two-stage compressed carbon dioxide heat pump water heater system studied in this paper is based on the direct-heating system.The purpose is to achieve higher effluent temperature.Firstly,this paper makes a theoretical analysis of the circulating carbon dioxide heat pump water heater system,then designs and chooses the components of the system.Finally,the temperature,pressure,flow,power and other measurement points are arranged and debugged.According to the influence of refrigerant charge on the performance parameters of the system,the best refrigerant charge is selected.From the point of view of outdoor environment temperature and cooling water flow rate of air cooler,the operation characteristics of the system are studied experimentally.The data are analyzed and the circulating water tank is improved.Finally,the data before and after the improvement are compared to provide effective data support for the optimization system.The results show that:(1)when the cooling water flow rate of the air cooler is 2.0L/min and the outdoor ambient temperature is-10℃,0℃and 10℃,with the increase of refrigerant charge,the system calorific capacity,compressor exhaust pressure and compressor power consumption continue to increase;the COPh of the system and the outlet water temperature of the air cooler first increase and then decrease,thus the optimal refrigerant charge of the system is determined to be 3.25 kg.(2)When the cooling water flow rate of air cooler is 1.5L/min,2.0L/min and 2.5L/min respectively,and the outdoor ambient temperature is-10℃,0℃and 10℃ respectively,when the outdoor ambient temperature rises,the outlet water temperature,compressor exhaust pressure,system calorific value,compressor power consumption and COPh of the system also increase continuously,and the temperature of each measuring point of the water tank rises.It takes 2500 s,2250s and 2200 s for 50 L water in the tank to reach 70℃,respectively.It can be concluded that the higher the ambient temperature is,the shorter the time it takes for the water temperature to reach the user’s required temperature.(3)When the cooling water flow rate is 1.5L/min,2.0L/min and 2.5L/min,and the outdoor ambient temperature is-10℃,0℃and 10℃,the outlet water temperature,compressor exhaust pressure,compressor power consumption of the air cooler are continuously reduced,the system calorific value and COPh are increased,and the temperature stratification of each measuring point of the water tank is not obvious.It takes 2200 s,2250s and 2500 s for 50 L water in the water tank to reach 70℃,respectively.It can be concluded that the larger the flow of cooling water,the longer it takes for the water temperature to reach the user’s required temperature.(4)When the cooling water flow rate of air cooler is 2.0L/min and the outdoor ambient temperature is 0℃,the system performance is obviously improved after the retrofitting of the circulating water tank.The outlet water temperature,system heat production and COPh of the air cooler are greatly increased,the exhaust pressure and power consumption of the compressor are obviously reduced,and the ambient temperature is 0℃,when the cooling water flow rate of the air cooler is 2.0L/min,the temperature of the water tank is obviously increased.It can be seen from the change of distribution that the temperature stratification of the improved water tank is more obvious,and the water at the top of the water tank meets the demand more quickly.The time for 12.56 L water,31.40 L water and 50.24 L water in the tank to reach 70℃was increased by 200 s,250s and 180 s,respectively. |
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