Experimental And Optimization Of Heating Performance Of Enhanced Vapor Injection Air Source Heat Pump

Air source heat pump(ASHP)has many problems in the application of "coal to electricity" project in North China,such as large compression ratio,high discharge temperature,insufficient heating capacity and poor coefficient of performance.Aiming at the above problems,a series of experimental studies and theoretical analysis on air source heat pump are carried out.Firstly,the theoretical cycle thermodynamic calculation model is established,and the performance of single-stage compression,enhanced liquid injection,enhanced vapor injection with economizer,enhanced vapor injection with flush tank and two-stage coupling system are compared.The enhanced vapor injection with economizer system is selected as the theoretical system of cryogenic air source heat pump.By comparing the performance differences of the commonly used HFCs refrigerants in the enhanced vapor injection with economizer,R410 A was selected as the refrigerant of the cryogenic air source heat pump.Then,based on the optimized circulation system and refrigerant,an enhanced vapor injection air source heat pump with economizer is designed.Through basic experiments,its operating characteristics under variable operating conditions are tested.Based on this,the influence of vapor injection on the performance parameters of heat pump is analyzed.The results show that vapor injection can not only effectively reduce the discharge temperature of air source heat pump,increase heating capacity and COP,but also make the air source heat pump operate steady at lower temperature.Finally,a numerical simulation model is established.On the basis of model validation,the quantitative control of vapor inection,compressor optimization,economizer optimization,flasher system and economizer system comparision are studied by using the model.The results show that:(1)there is an optimum relative vapor injection mass to maximize COP,and the optimum relative vapor injection mass is between 4% and 10%;(2)there is an optimum first-stage volume ratio to maximize COP,and the optimum first-stage volume ratio is between 1.35 and 1.6;(3)increasing the number of economizer plates can effectively improve the performance parameters of the enhanced vapor injection air source heat pump.The lower the ambient temperature,the more efficient the economizer plates are to enhance COP of the system.;(4)The stability of the economizer system is much higher than that of the flash tank system,and the difference between the performance parameters and the flasher system is not large,so economizer system is more suitable for the application of "coal to electricity" project.