Study on analytical solution model of heat transfer of ground heat exchanger in the protection engineering structure

In order to eliminate the disadvantages of the high cost of underground pipe drilling and space occupation, according to the relevant practices of existing energy underground structures, the idea of embedding the buried pipe of the ground source heat pump system into the tunnel lining of protection engineering was proposed. An analytical model of the heat transfer process of the ground heat exchanger was established, and the explicit expressions of the calculated parameters were obtained. The reliability of the model was verified by the existing experimental data. The model was used to analyze the influence of different air temperature and flow rate on the heat transfer performance of the ground heat exchanger. The study found that every time the air temperature rises by 1 degrees C, the heat transfer per unit passageway length was reduced by about 200W. The increase in air flow velocity has a limited impact on the heat transfer. The method of enhancing heat transfers by increasing the flow velocity can only be performed at a small flow velocity. In the total heat exchange per unit length, the proportion of the heat exchange on the air side and the heat exchange on the surrounding rock side affect the protection capability of the project in an isolated state. The greater the proportion of heat exchange on the side of the surrounding rock, the stronger the protection capability in the isolated state. (C) 2021 Elsevier Ltd. All rights reserved.