Thermal Resistance of Double U-tube Geothermal Heat Exchanger Based on CFD Technology

Taking the geothermal heat exchanger as an object, the heat exchanger thermal resistance of each link was simulated by the Fluent software. A double U-tube geothermal heat exchanger of two-dimension model was established, and the heat transfer process of the drilling was simulated. The theoretical results and simulation results were compared to verify the accuracy of the simulation model, and the effect of the accuracy with the changes of tube pitch, PE tube outer diameter and borehole radius for thermal resistance of PE pipe and borehole were discussed. The results show that the simulation and theoretical values of the thermal resistance of PE pipe and borehole outside are very similar, while the accuracy of the calculated by the theory of borehole thermal resistance is poor. There is a large deviation between the calculated value and the analog value. Tube pitch and drilling radius have no effect on the relative error of the theoretical value and analog values. The relative error of the borehole thermal resistance between the theoretical value and the analog value grows while the PE pipe diameter increases. It can provide a good reference for the design of ground source heat pump.