Analysis And Experiment Of The Ground Source Heat Pump System Based On Four-boreholes Model

Ground source heat pump has the advantages of environmental protection,energy saving and high efficiency, strongly supported by China. As the mostimportant part of the ground source heat pump, ground source heat exchanger iscomposed of a plurality of vertical U type pipes buried in the ground. Most researchon the model of heat transfer of heat pump system study single borehole. The modelof multi-boreholes base on Green function method of superposition. The main work ofthis paper:1) Based on the finite line source theory, using the Green function method andthe virtual heat exchange method, established the heat transfer model in cylindricalcoordinates.As the g function definition, the g function of the four drill boreholesmodel is established in this paper.Using numerical simulation method, the g functionis improved, and is suitable for the short time step.2) According to the dynamic characteristics of ground source heat pumpsystem,using the model in this paper,the changing of the soil temperature field andheat exchanger performance are analysed in the actual operation. According to theprinciple of system failure, the human factors are analysed, and according to theexisting research, suggestions for improvement are supplied.3) Base on the thermal response test, the experimental system is made,in whichthe outlet water temperature is a constant. System has two heat pumps for cooling(heat) unit, Siemens PLC as the control core, with high precision measuringinstrument and computer software to monitor module.Under the winter heatingcondition (extract underground heat) experimental data is get.4) According to the comparison of experimental and simulated data, the accuracyof the model established in this paper suit for the need.