| This paper introduces an energy storage interconnected heat pump,which connects the air source heat pump with the water source heat pump by a phase change energy storage equipment,can keep the coefficient of performance(COP)of air source heat pump in a reasonable range(3.0-3.5).Firstly,this paper studies the performance coefficient and refrigerant compression ratio of different refrigerants in the energy storage interconnected heat pump when the ambient temperature ranges from-25℃ to-5℃,the different temperature of water produced at the air source side and the different temperature of user water supply.Secondly,numerical simulation is used to investigate the melting and solidification process of the paraffin C17 in spherical heat storage unit.On this basis,the influence that the spherical wall temperature,spherical heat storage unit size and the PCM initial temperature on the melting process is investigated.Finally,the three operating modes are summarized by exploring the system’s operating control strategy,and according to the experimental data in a renovation project,the different parameters of the two operating modes are investigated.And the conclusions are compared and verified.By the analysis above,it is found that at the ambient temperature between-20℃ and-5℃,when R410A/R134 a or R404A/R134 a are used for the refrigerants of air source side and the water source side,the supply water temperature at the user is 55℃,and the COP of the whole system is higher,which can reach above 3.5;with the ambient temperature growth,the COP of the energy storage interconnected heat pump system using R410A/R134 a refrigerant combination is increased obviously.Among the main factors affecting the performance of the energy storage interconnected heat pump system,the temperature of the outlet water loop of the phase change energy storage device has the least impact on the COP,and the end of water supply temperature has the most impact on the COP.When the user’s temperature supply temperature is 45℃ and the ambient temperature is lower than-5℃,the refrigerant combination of R404A/R134 a can each the highest COP;When the user’s temperature supply temperature is 50℃ and the ambient temperature is from-5℃ to 12℃,the refrigerant combination of R410A/R134 a can each the highest COP;When the user’s temperature supply temperature is 55℃ and the ambient temperature is lower than-16℃,the refrigerant combination of R404A/R134 a can each the highest COP;When the ambient temperature is from-5℃ to-16℃,the refrigerant combination of R410A/R134 a can each the highest COP.According to the numerical simulation on the melting and solidification process,it is found that the influence factors which arranged from large to small on the melting process are the diameter of spherical phase change unit,the spherical wall temperature and the initial temperature of PCM.On the solidification process,two factors that the low thermal conductivity of solid phase and the increasing of the solid phase attach the liquid phase impede the convective heat transfer between the liquid phase and the spherical wall.Thus,the rate of solidification process is reduced.According to the comparison between melting process and solidification process,the complete melting time is less than the complete solidification.The convective heat transfer between the liquid phase and the spherical wall can accelerate the melting process.Based on the experimental data from the renovation project,the operating strategies of the energy storage interconnected heat pump are summarized,including the direct heating mode of air source heat pump,the combined heating mode of phase change energy storage device and water source heat pump,and the combined heating mode of the air source heat pump and the water source heat pump.And it is verified that the outlet water loop temperature of phase change energy storage device has a little effect on the COP of the system.Finally,according to the experimental data of compressor and evaporator,in the high relative humidity region,the frosting problem which arouse by the air source heat pump side reduces the energy conservation.However,the compressors on the air source side and water source side of the system remain stable at 80% relative humidity,thus,the system ensures stable heating. |
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