To effectively describe the heat transfer process of underground buried pipe heat exchanger systems and facilitate the optimal design of buried pipe heat exchanger systems. A coupled analytical model of coaxial sleeve heat exchanger considering soil and borehole heat transfer processes was established using the method of layered composite medium and segmented iterative calculation. The rationality of the model was verified based on experimental and numerical simulation results. The influence of initial ground temperature distribution and temperature ratio on the performance of buried pipe systems was analyzed using a model. The results indicate that ignoring the influence of the variable temperature layer will underestimate the heat transfer capacity of the heat exchanger
and the impact on the heat transfer performance of shallow buried pipes is greater than that of deep layers. In addition
it was found that the heat exchange rate is not determined by a higher inlet fluid temperature
but by a larger difference between the inlet fluid temperature and the initial ground temperature.
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