Model Considering Thermal Conduction And Groundwater Advection Of Soil Viewed As Porous Medium And Numerical Simulation On Soil Temperature Field Around Underground Heat Exchanger

Ground coupled heat pump (GCHP) takes the soil as heat source in heating and heat sink in cooling mode. The soil temperature is higher than the air temperature in winter and lower in summer, so it's advantage for heat transfer to set the heat exchanger in the soil. GCHP can reduce the wastage of coal and save oil and natural gas, which will help the country improve the energy structure and reduce the amount of released gas to protect the environment and achieve the goal of sustainable development. So the GCHP is an efficiently economic and green way for heating and air conditioning.One of the key techniques for GCHP popularization and application is to perfect heat transfer models for the ground heat exchanger to simulate the actual heat transfer process .The model of the fluid in the U-tube and the coupled thermal conduction and groundwater advection model of underground temperature field around the U-tube were set up .The heat transfer and flow of the fluid in the U-tube ,the heat transfer between the U-tube and soil, and the soil temperature field was simulated. The GAMBIT was used to constitute physical model. The Fluent software was used to carry out the numerical simulation study .The creative is placed in two points .On the one hand ,the actual shape of the U-tube was considered to simulate the true flow of the fluid in the tube .On the other hand , soil was viewed as saturated porous medium considering groundwater advection.Compared with the mathematical model used by early investigators, in which the U-tube was equivalent as a cylindrical heat source ,soil was regard as solid considering heat conduction only ,it' s an essential progress.The fluid temperature change in the U-tube, soil temperature field and thermal influencing radius were studied in the seepage situation firstly .Then ,compared with the results without seepage, it can be seen that seepage is useful to heat transfer of underground heat exchanger. In addition ,the influencing factors, such as soil property, including heat conduction coefficient , specific heat, density, porosity, pervasion rate and different soil types , backfill material, the U-tube material, which affect soil temperature field, thermal influencing radius and the quantity of exchanging heat of underground heat exchanger.It is worthy to guide the design of U-tube underground heat exchanger.