The Research Of The Ground Temperature Field Around The Heat Exchanger In Ground-coupled Source Heat Pump Hot Water System

Ground-coupled source heat pump hot water system is a highly efficientenergy-saving system. It uses the geothermal resources underground as heat source tosupply hot water energy efficient systems by transferring energy between soil andpiping systems around the building. This paper takes ground-coupled source heatpump hot water system of Tianma student apartments in Changsha as a research object.In this paper, the ground temperature field around the double-U heat exchanger isstudied by combining engineering experiments and ANSYS software method. On theone hand, the Pt temperature seniors are set in different depth and different radiusaround the double-U heat exchanger. Over more than five months the groundtemperature is tested to study the temperature changing regularity around thedouble-U ground heat exchanger. On the other hand, based on the actual project, thispaper uses ANSYS software to simulate the ground temperature field distributionaround the double-U heat exchanger by simplifying theoretical model, then comparessimulation results and experimental data to verify the reliability of the modelsimulation. And then this paper uses the model simulation to analyze the maininfluencing factors of the ground temperature field.The experiments research and simulation results show that:(1) The original ground temperature of the underground10m below basicallymaintains a constant, and gradually rises with depth. The temperature gradient isabout0.02℃/m;(2) The heat pump units which stops running in a month has no effect on theground temperature that is0.8m distance farther away from the work wells. Becausethe soil thermoresistance is huge and heat recovery is slow;(3) During five months tested, because the soil thermoresistance is huge and heattransfer is slow, the farther the distance from the heat exchanger, the smaller thechanges in magnitude of the ground temperature, and the temperature begins tochange appearing a certain delay. The experiments research results show that theradius of the thermal effect around the heat exchanger is between2.4m and3.2m;(4) This paper uses ANSYS to simulate the ground temperature field around theheat exchanger by simplifying theoretical model, and compares simulation results andexperimental data. Then we find out that the experimental data of the ground temperature fluctuate around the simulation curve, and agree with each other well;(5) This paper uses the model simulation to analyze the main influencing factorsof the ground temperature field. The results show that the best distance between heatexchanges is5m for avoiding thermal interference, in order to ensure the normal andefficient operation of the heat pump units; And The greater the heat pump unit operate,the greater the gound temperature decline, but in conditions that the accumulated heatis the same, the groud temperature decrease is basically the same.