The Research Of The Heat Transfer Characteristics Of The Rock And Soil In Nanning Basin Under The Effects Of Vertical Double U Type Buried Pipe Heat Exchanger

The property of the ground source heat pump largely dependents on the property of the underground pipe heat transfer, and underground pipe heat transfer performance and the surrounding rock and soil heat transfer characteristics are closely related. As the the hydrogeological and engineering geological conditions are different in different areas, the soil heat transfer characteristics will also be different. In this paper, we base on in-situ test of the temperature variation around the soil of the underground pipe, where the underground pipe belongs to a certain vertical double U type ground source heat pump project in Nanning.and then make the numerical simulation, and the paper also discusses the characteristics and applications of the of rock and soil heat transfer in Nanning basin.The paper explores the rock and soil temperature variation law under the action of the double U type buried pipe heat exchanger through in situ test and carries out the numerical simulation research. The test results show that:Firstly, through the calculation the minimum depth where the temperature of the rock and soil layer is constant throughout the year is9.7m. According to the measured data of soil temperature, the temperature variation at the depth of below the surface of10m is small, and the result is consistent with the conclusion; Secondly, in the deepest measurement point of the monitoring hole the temperature fall by small in the unit operation period, but in recovery period the temperature do not reply. Other measurement point temperature changed with the unit operation condition, in the unit run-time the measurement point temperature is lower when it stop running the temperature of the measuring point would rebound, but it fail to back up to the original ground temperature; Thirdly, after two years of unit operation, the temperature of each measuring point in the hole which is5m far away from the well is decreased and the largest decline amplitude is1.5℃.It shows that the thermal scope of the engineering well has reached5m, but has little effect.Then I made a model with the finite element software ABAQUS to simulate the heat transfer of the shaly rock layer, and then the simulation results were compared with the experimental data, and they were basically consistent.