Research On Heat Transfer Characteristics Of The Deep Buried Pipe Type Of Energy Pile

With the development of China's social economy,the air-conditioning system(heating and cooling)accounts for 25%-30% of the total energy consumption.The traditional energy has the disadvantages of environmental pollution,and the development of clean energy is imminent.Among all kinds of new and renewable energy sources,geothermal energy stored under the earth's surface is effectively used for air conditioning systems.Based on the energy pile technology of geothermal development,a new deep buried pipe energy pile technology is proposed in this paper.The technology not only makes full use of the advantages of the buried pipe energy pile in the pile,but also can use the deeper geothermal energy to improve the heat transfer of a single energy pile.The structure of the new energy pile is flexible,which can design the buried depth of the deep well according to the heat exchange demand,and realize the efficient and economic utilization of geothermal resources.In this paper,the heat transfer characteristics of energy pile are studied by means of theoretical analysis,field test and numerical simulationThe main work and research results of this article are as follows:(1)This paper introduces in detail the overall design of the test base of deep buried pipe energy pile,the design of buried pipe of heat exchange hole,the design of inlet and outlet valves of heat exchange pipe,and the layout design of sensors in the heat exchange hole.The construction technology of deep buried pipe type energy pile after drilling is put forward.According to the design and construction technology,the construction of deep buried pipe energy pile is carried out.(2)The temperature field distribution of deep buried tubular energy pile under different working conditions is studied.The temperature field distribution of deep buried tubular energy pile under different working conditions is studied.When the heat transfer is stable,the temperature of the inlet pipe changes obviously with the increase of the heat transfer depth,while the temperature of the outlet pipe does not change significantly with the heat transfer depth.Among them,the temperature of the inlet pipe of the upper part of the pile foundation changes fastest along the heat transfer depth,while the temperature of the outlet pipe changes slightly;the temperature change of the inlet pipe along the heat transfer depth of the lower part of the deep well is larger than that of the outlet pipe.(3)The double U-tube heat exchanger model of energy pile was established by ANSYS software,and the accuracy of the model was verified by comparing with the existing test results.The temperature field distribution of deep buried tubular energy pile under different working conditions is studied.With the increase of the set inlet water temperature,the temperature difference of the energy pile increases gradually,the inlet temperature is 30 ?,the temperature difference between the inlet and outlet of the energy pile is 4.31 ?,the inlet temperature is 35 ?,the temperature differencebetween the inlet and outlet of the energy pile is 6.18 ?,and the temperature difference increases by 1.87 ?.(4)The heat transfer efficiency of the whole structure of the energy pile under different working conditions is calculated and analyzed.When the heating power is3.5kw,the total heat transfer of the deep buried pipe energy pile is 3200.63 w,and the heat transfer per linear meter is 32.01w/m;when the heating power is 5.5k W,the overall heat transfer is increased by 1827.7w,the heat transfer per linear meter is increased by 10.6w/m,and the heat transfer is increased by 53%.With the increase of heating power,the heat transfer of deep buried pipe energy pile increases and the heat exchange efficiency increases.Through the research on the heat transfer characteristics of deep buried pipe energy pile,it will provide a theoretical and practical basis for the popularization and application of energy pile technology.