Study On The Cold Storage Application And Heat Recharge Of Ground-coupled Heat Pump System In China Northern Buildings

In the actual operation,the ground-coupled heat pump systems(GCHPs)has the problem of extraction and recharge heat imbalance in soil side,which seriously affects the size of COP and the long-term efficient operation.Aiming at the situation that the northern part of the building extracts more heat in winter than recharges heat in summer,this paper studies a kind of heating method that does not increase the extra heat source,that is,the cold storage application in summer and recharge by moderately cooling in late spring and early autumn which can increases the recharge of heat to the soil side,in order to expanding or promoting the application range and efficiency of the GCHPs.The room heat balance equation was established by MATLAB programming software in summers,and the finite difference numerical solution of the external wall unsteady heat transfer and the radiated floor unsteady heat storage were performed.The results show that the temperature distribution of the wall shows a law of decreasing along the thickness direction,and the heat transfer increases first and then decreases.The temperature distribution of the floor calculation unit is circular with the radial coil as the center,which is the lowest near the radial coil and outward gradually.The variation law of return water temperature for radiant floor cooling is discussed,which is related to the heat transfer of external wall,window,indoor personnel and equipment,and floor heat storage,but the effect is different.When the cooling system is opened,the floor heat storage has a larger value,which requires more cooling capacity and makes the return water temperature higher.With the operation of the system,the temperature is greatly affected by the heat transfer of the external wall and the window.Within one day,the return water temperature generally showed a trend of increasing first and then decreasing.Taking a building of 5000m~2 and floor radiant cooling temperature 12?in Jinan climate as an example,the actual engineering test data analysis and dynamic simulation model of TRNSYS was built.And the cooling effect and COP of the system were simulated in summer,late spring and early autumn.The results show that under the underground pipe direct supply system,good results are achieved.The average COP value of the system is 7.2,the energy-saving effect of residual cooling in summer is obvious.At late spring and early autumn,the buried pipe direct supply system had good thermal comfort degree.However,the average COP value of the system in the early spring is 5.0.The system has certain energy-saving effect in the late spring.In the early autumn,the average COP value of the system is 1.9.The energy consumption effect of the system in the late autumn is obvious.In days of the system's annual recharge,the total power consumption of the circulating pump is 78890 KWh,the total heat dissipation account for 91.7%of the required recharge heat.The average COP value of the system during the recharge period is 5.7.Combining with the actual project,it is compared with the solar collector recharge mode.The analysis shows that the two ways are technically feasible.But with 10 years as a lifetime calculation,the annual cost of the unit building area supplemented with the same amount of heat,the buried pipe heat recovery system is 19.8%of the heat of the solar collector.The former has obvious economic and technical advantages,which is an effective way to solve the underground thermal imbalance of GCHPs in the northern region.