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Soil thermal imbalance in borehole heat exchangers (BHE) severely constrains the efficiency of the ground source heat pump system (GSHP), while traditional phase change backfill material is prone to leakage and soil contamination. Based on this, a novel enhanced backfill material - microencapsulated phase change material (MPCM) is proposed in this paper. A three-dimensional model of BHE backfilled with ordinary grout and MPCM is developed and validated against experimental data. Effects of backfill material on thermal performance of BHE and system efficiency are investigated. The results reveal that incorporating MPCM into backfill soil can significantly enhance system performance. Compared with ordinary grouting, the MPCM-enhanced BHE can achieve 6 times increase in heat transfer rate and 15.8% improvement in coefficient of performance (COP). This enhancement is mainly attributed to the large latent heat release. Moreover, MPCM backfill reduces the thermal influence radius of soil temperature by 25%, alleviating the long-term soil thermal imbalance. This study provides new insights into the optimization of BHE and mitigating soil thermal imbalance, which offers practical guidance for the design and deployment of advanced geothermal systems.

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Enhanced Thermal Efficiency of Borehole Heat Exchanger with Microencapsulated Phase Change Backfill Materials

  • 会议论文

  • 发表日期：

    2025年

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  • Lingling Xu,
  • Qianbing Li,
  • Haonan Li

摘要

Soil thermal imbalance in borehole heat exchangers (BHE) severely constrains the efficiency of the ground source heat pump system (GSHP), while traditional phase change backfill material is prone to leakage and soil contamination. Based on this, a novel enhanced backfill material - microencapsulated phase change material (MPCM) is proposed in this paper. A three-dimensional model of BHE backfilled with ordinary grout and MPCM is developed and validated against experimental data. Effects of backfill material on thermal performance of BHE and system efficiency are investigated. The results reveal that incorporating MPCM into backfill soil can significantly enhance system performance. Compared with ordinary grouting, the MPCM-enhanced BHE can achieve 6 times increase in heat transfer rate and 15.8% improvement in coefficient of performance (COP). This enhancement is mainly attributed to the large latent heat release. Moreover, MPCM backfill reduces the thermal influence radius of soil temperature by 25%, alleviating the long-term soil thermal imbalance. This study provides new insights into the optimization of BHE and mitigating soil thermal imbalance, which offers practical guidance for the design and deployment of advanced geothermal systems.