Research On Double Cycle Cooperative Supply System Of Low Temperature Air Source Heat Pump

In order to save energy and reduce emissions,and control winter haze,it is necessary to reduce coal consumption for heating in winter.Air source heat pump heating technology has become the first choice for coal to electricity.It is difficult for ordinary air source heat pump to operate normally when the ambient temperature is below-15℃.Because of the low temperature environment temperature,the volume efficiency of the compressor is greatly reduced,the exhaust temperature is too high,the evaporator frosts frequently,the unit has less heat,and the economy is very poor.This restricts the application of air source heat pump technology in the north cold area where heating demand is most urgent.In order to solve the above problems,this paper puts forward for the first time the dual-cycle combined supply system of low-temperature air source heat pump,which is suitable for the cold areas above-25℃and has the function of heating and hot water for daily use.Realize the multi-function integration of low temperature air source heat pump.The system consists of two circulation loops:heating loop and domestic hot water loop.The refrigerant R410A is used in both loops,both of which are single-stage operation and heat transfer through the economizer.After the refrigerant in the hot water circuit is boosted,a part of the refrigerant is diverted into the ejector,which is used to raise the suction pressure of the compressor in the heating circuit,so that the compressor in the heating circuit can operate normally at low temperature.The refrigerant in the hot water loop evaporates in the economizer,and the refrigerant in the heating loop obtains a greater degree of super cooling in the economizer.In this paper,the design of dual-cycle combined supply system of low temperature air source heat pump is completed,and the cycle thermodynamic calculation and economic analysis are carried out.The theoretical calculation shows that when the evaporation temperature of the heating cycle is-35℃,the COP₁ of the heating loop can reach 2.32,the COP₂ of the heating water loop can reach 1.33,and the overall COP of the system can reach 2.11.The performance of the system is always higher than that of the ordinary single-stage compression heat pump system and the supplementary enthalpy heat pump system.It shows that the dual cycle combined power supply system has good low temperature adaptability.The experimental results show that the overall COP of the system can reach 2.75when the ambient temperature is-12℃and the heating outlet temperature is 41℃.The heat pump system can still work normally at ambient temperature of-25℃,and COP can reach 2.15.Four-way valve reverse circulation defrosting effect is good,defrosting time is 5⁶ minutes,evaporator surface is free of residue,drainage is smooth,indoor temperature is reduced to 1²℃.Through theoretical analysis and experimental test,the dual-cycle combined supply system of low-temperature air source heat pump proposed in this paper can meet the heating and domestic hot water demand in cold areas of northern China,which proves the feasibility of the system.