Study On Performance Of Trans-critical CO₂ Air Source Heat Pump In Cold Region

With the rapid economic development in China,the demand for energy is also growing.In order to solve the problems of large energy consumption and environmental pollution caused by traditional heating methods in China,the energy-saving and environment-friendly heating methods and policies such as "coal to electricity" and "energy saving and emission reduction"have been put forward.The application of trans-critical CO2 air source heat pump heating in cold regions of China can reduce the damage to the environment caused by the use of freon and other refrigerants.And the air source heat pump because of its high efficiency and low energy consumption,stable work,clean and no pollution,to improve the smog pollution of the city is of great significance in our country.Under this background,this paper proposes a kind of trans-critical CO2 air source heat pump system suitable for cold region.Through numerical calculation,simulation analysis and experimental verification.The operation characteristics of the air source heat pump under different working conditions are studied,and the economic and environmental protection analysis of the air source heat pump is carried out,and the results are as follows:（1）Through numerical calculation,at the same heating temperature,environment temperature at-20℃-10℃,the COP value of the unit increases with the increase of ambient temperature;at the same cooling temperature,when the ambient temperature varies from 26℃to 38℃,the COP value of the unit decreases monotonically with the increase of the ambient temperature;The COP value of CO2 air source heat pump unit is always higher than that of other three working medium units.（2）Through TRNSYS simulation calculation and the experimental research,the system is suitable for winter heating in cold regions and meets the requirements of summer comfort.The performance coefficient,input power,heating power and refrigeration power of the system are greatly affected by the ambient temperature.In cold regions,the accumulative input power of air source heat pump heating system in the coldest month is 2094.21 kW,the accumulative heating power is 4258.46kW,the accumulative input power in the hottest month is 668.14kW,the accumulative refrigeration power is 2014.15kW.The temperature of water supply and water return of air source heat pump is stable in heating period and cooling period,and the energy supply effect is better.（3）Through the experimental research,the temperature of supply and return water fluctuates under the influence of ambient temperature,but the fluctuation range is acceptable.The air source heat pump heating system can provide a stable water supply temperature.COP values of unit and system increase first and then decrease with the change of ambient temperature,and higher COP values indicate better system performance.The experimental values of supply and return water temperatures and COP are in good agreement with the simulated values,and the relative errors of the two are small,indicating the accuracy of the air source heat pump model.（4）Through the analysis of economy and environmental protection,the annual cost of trans-critical CO2 air source heat pump system is small and the economic benefit is high;trans-critical CO2 air source heat pump heating system can effectively reduce the emission of carbon dioxide,sulfur dioxide,nitrogen oxides and soot,and has good environmental benefits.