Simulation And Experimental Study On Heat Transfer Performance Of Ground Heat Exchanger

The ground-source heat pump technology is a kind of energy-savingair-conditioning technology, using shallow geothermal energy for building heatingand cooling and this technology is widely used with the emphasis of buildingenergy-saving. The ground source heat pump system is divided into water and groundsource heat pump system. Because of the limitation of water resources and otherconditions, the application of water resource heat pump has been limited much.Ground heat pump technology has broad application due to avoiding the shortcomingsof the water source heat pump. But ground heat pump has just been used widely inrecent years. Due to the complexity of underground soil conditions, there are stillmany problems need to solved about ground heat exchanger.This dissertation analyzed the heat transfer process of ground heat exchanger,and used the combined way of numerical simulation and experiment to study the heattransfer performance of single、double U-shaped and casing heat exchanger, and thechanges of soil temperature field in different flow rates, pipe layout, pipe diametermatching and different forms of workflow. Through the numerical simulation andexperimental test, this dissertation got the following conclusions:The simulation results show that, with the flow rate increasing, the heat transferof ground heat exchanger increases; the effect of the tube spacing60mm singleU-shaped heat exchanger is higher than the tube spacing50mm; the single U-shapedheat exchanger heat transfer of DN32as pipe diameter is higher than DN25as pipediameter; when the double U-shaped ground heat exchanger uses the form of crosspipe, the effect is better than others; The casing heat exchanger which inner pipe asinlet、outer pipe as outlet coaxial layout has the better heat transfer effect than whichouter pipe as inlet、inner pipe as outlet; When the heat exchanger uses diametermatching form of DN32as inner tube, the amount of casing heat exchange is higherthan DN25as inner tube; the effect radius of the surrounding soil temperature causedby the three buried heat exchangers grew to2meters.According to the simulation results, this dissertation select tube spacing of60mm、the DN32single U-shaped pipe, cross form of double U-shaped pipe and theinner pipe as inlet outer pipe as outlet、 coaxial tube heat exchanger to experimental study. And study the heat transfer performance of ground heat exchanger in differentflow rates and the change of soil temperature filed in runtime. The results show thatthe rate of increasing of soil temperature three meters underground graduallydecreases with time growth; and the temperature difference between inlet and outletdecreased with the flow rate increasing, but the amount of heat exchanger increased.