Nanjing Summer Solar Radiation Affect The Operating Performance Of The Vertical Borehole Ground Source Heat Pump

Recent years, with lots of advantages such as highly effective performance, energy saving and environmentally friendly, ground source heat pump(GSHP) is drawing more and more attention. One of the key technologies for the applicant and popularizing of the ground source heat pump is to the heat transfer issue between the tube and the soil. Therefore, it is extremely significant to optimize the heat transfer model of the heat exchangers in GSHP in order to simulate the real heat transfer process more accurately. The mathematical model is build via theoretical analyses and computer model is build via GAMBIT software. According to the laboratory of Nanjing Normal University, we use FLUENT software to simulate and calculate the three-dimensional heat transfer and flow process of the GSHP. During the former researching process, we supposed to consider the ground surface as the first boundary condition, which means the ground temperature below it is nearly constant, equals the average local temperature plus two degree centigrade.A numerical simulation is introduced to establish a three-dimensional heat transfer model of GSHP by FLUENT and theoretical analyses. Do the simulations to the single U-tube boreholes under the different upper surface boundary conditions. Through the comparison of the temperature of outlet of the borehole and the flow direction under different upper surface boundary conditions, the author analyses the effects of solar radiation on the performance of GSHPThe results show that with the same 60m's long ground borehole and the same temperature at the inlet, the temperature of the out let tends to be 0.28℃higher, and the heat transfer tends to be 3.136w per meter less if solar radiation is taken into account. By analysis, the ground borehole should be 5% longer if solar radiation is taken into account than if not. All these data results could be reference in the design of GSHP.