Abstract:To promote the efficient development of shallow geothermal resources in coastal cities and address the issues of limited heat exchange efficiency of traditional energy underground structures and insufficient adaptability of ground burial pipe technology, taking the test section of an assembled energy shaft in Shanghai as the research object, a thermodynamic coupling numerical model including concrete lining segment, surrounding soil and PERT heat exchange tubes is constructed to systematically explore the influence of key design parameters on the heat exchange efficiency and the law of structural stability. The results show that the flow rate of the heat exchange medium should be controlled at 0.6~0.9 m/s, which can not only ensure the heat exchange efficiency, but also avoid the waste of operating costs. The pipe spacing is preferably 0.25~0.30 m, which can effectively reduce the thermal interference between pipes while also taking into account the heat transfer efficiency per unit area of the lining. In terms of structural deformation, the lining is continuously compressed under the action of low-temperature fluid, and the deformation at the measurement points near the inlet of the heat exchange tubes is the most significant. In terms of stress distribution, the bottom of the outer edge of the lining near the inlet of the heat exchange tube is the weak tensile area of the structure. The maximum compressive stress is within the material safety range. The surrounding soil shows the characteristic of “first compression, and then tension”.
