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The core component of the ground source heat pump (GSHP) system is the buried pipe heat exchanger. It is critically important to analyze its thermal exchange efficiency for safe and consistent functionality. Taking the double U-shaped buried pipe group as the study subject, this research constructed a three-dimensional model using computational fluid dynamics (CFD). The influence of the spacing and drilling depth on the heat transfer performance was analyzed. Further investigation was conducted on how 15 years of uninterrupted operation of the buried pipes affects the temperature field of the surrounding soil. The spacings between buried pipes were set to 4 m, 4.5 m, 5 m, 5.5 m, and 6 m, with drilling depths fixed at 150 m and 200 m. The research findings indicated that an optimal spacing of 5 m and a depth of 150 m were identified. Following a continuous 15-year period of operation, the mean temperature of the soil reached 15.5 °C. This represents a modest increase of just 0.45 °C when compared to the initial soil temperature, demonstrating effective soil temperature recovery and the absence of heat or cold accumulation. This study provides references for the design and construction of double U-shaped buried pipes in the GSHP system.
Ren et al. (Wed,) studied this question.