Experimental Study On The Operation Characteristics Of Single-stage Compression CO₂ Heat Pump Water Heater System

At present,our country is in the stage of rapid economic development and increasing scientific and technological forces.At the same time,the rate of increase in energy consumption is also increasing year by year.The energy crisis and the environmental pollution of globalization have already become an unavoidable issue for us at present.Problems such as the destruction of the ozone layer and the greenhouse effect have become increasingly serious.Fluorine-based refrigerants have gradually been banned from use,and the research on new energy sources is imminent.The operating characteristics of the single-stage compression air source CO₂ heat pump water heater system studied in this study are of great significance for energy conservation and environmental protection.The CO₂ heat pump water heater have a higher system coefficient of performance?COP?than an ordinary heat pump water heater by no pollution and the unique characteristics in a transcritical state about CO₂.What's more,some effective basis is provided for analysis in the research,to some extent,the pace of commercialization of air-sourced CO₂ heat pump water heaters is accelerated in China.In order to further understand the operation characteristics of the single-stage compression CO2 heat pump water heater system,the CO2 heat pump water heater system test bed was designed and built.First,the CO₂ heat pump water heater experiment system,data acquisition system,electrical control system were analyzed and designed theoretically.Then the key components in the experimental system are designed and selected,and the test rig is debugged.In view of the changes in the parameters of the opening of the throttle valve,the temperature of the outdoor environment,the water inlet temperature of the air cooler,the water flow and the exhaust pressure,the operation characteristics of the single stage compressed CO₂ heat pump water heater system are studied and the data analysis is carried out.The results of the study are as follows:?1?the compressor discharge temperature and the compressor pressure ratio decrease with the increase of the opening degree,and the COP increases first and then decreases with the increase of the opening degree.The opening degree is the optimal opening degree in the experimental system when the COP reaches its peak is 180 degrees.?2?In the range of ambient temperature of 6³3?,the system heat quantity,COP and the outlet temperature of gas cooler are increasing.?3?In the range of inlet water temperature of 12²0?,with the increase of inlet water temperature,the system heating capacity and COP are gradually decreasing,and the outlet water temperature is on the rise;?4?In the range of 1.5².5L/min water flow,as the flow rate of water increases,the heating capacity and COP of the system will gradually increase,and the outlet water temperature will gradually decrease;?5?With the gradual increase of exhaust pressure,the outlet water temperature of air cooler will rise first and then decrease,while the mass flow rate of CO2 and the suction pressure of compressor decrease.The temperature of the air cooler outlet CO2 increases with the increase of the exhaust pressure,and then continues to decrease.When the exhaust pressure continues to rise,the temperature drop of the air cooler outlet CO2 increases gradually,and the maximum drop temperature difference reaches 10.5?.The COP increases first and then decreases with the increase of exhaust pressure.The exhaust pressure corresponding to the peak value of COP is the optimal exhaust pressure in the experimental system is 83 Bar.