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<p>The mined-out areas formed by ore extraction have promoted the development of seasonal energy storage technology in underground spaces. Currently, most studies on the heat storage/release performance of backfills with embedded heat exchange pipes have idealized the operating conditions, such as constant fluid inlet temperature and flow rate. However, actual operating conditions are influenced by many factors like weather conditions, surface equipment, and heat load fluctuations, making them unstable. Therefore, this paper constructs a solar-assisted heat pump coupled mine backfill body heat storage system (SAHP-MBBHSs) based on TRNSYS simulation software and verifies the accuracy of the backfill heat exchangers (BFHEs) model through experiments. Considering the influence of various external factors on the operating conditions, we investigated the long-term seasonal heat storage/release performance of the BFHEs, focusing on the effects of solar collector area, U-tube spacing, thermal conductivity of backfill materials, and heat storage start/stop time. The results show that reducing the U-tube spacing increases the fluctuation amplitude of the average temperature of the backfill body, with the maximum average fluctuation amplitude difference reaching 16.6°C between the 11th and 15th years. Delaying the onset of thermal storage reduces the storage effectiveness of the U-BFHEs, while increasing the heat release effectiveness. During the thermal storage/release interval, heat loss to the surrounding rock does not exceed 4.7%, with the minimal overall impact. The thermal conductivity of the backfill body has the greatest effect on the heat transfer effectiveness of U-BFHEs, increasing from 1 W·m<sup>−1</sup>·K<sup>−1</sup> to 2 W·m<sup>−1</sup>·K<sup>−1</sup> resulting in respective increases of 58.8% and 39.2% in the heat transfer effectiveness during the 15th year of thermal storage/release. The total heat storage-release effectiveness of the U-BFHEs does not exceed 43.7%, indicating significant room for improvement. Utilizing seasonal thermal storage in the backfill body can effectively enhance the heating performance of SAHP-MBBHSs, with the maximum average APF and HSPF values reaching 3.85 and 5.43, respectively, during the 11th–15th years of operation, maintaining high efficiency even after long-term operation.</p>

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Long-Term Performance Investigation on Seasonal Heat Storage of U-Type Backfill Heat Exchangers in Mine Stopes Coupling a Solar-Assisted Heat Pump

  • 期刊论文

  • 发表日期：

    2025年5月5日

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  • Bo Zhang,
  • Zhiqiang Wu,
  • Lang Liu,
  • Chao Huan,
  • Yujiao Zhao,
  • Mei Wang,
  • Xueli Wang,
  • Xiaoyan Zhang

摘要

The mined-out areas formed by ore extraction have promoted the development of seasonal energy storage technology in underground spaces. Currently, most studies on the heat storage/release performance of backfills with embedded heat exchange pipes have idealized the operating conditions, such as constant fluid inlet temperature and flow rate. However, actual operating conditions are influenced by many factors like weather conditions, surface equipment, and heat load fluctuations, making them unstable. Therefore, this paper constructs a solar-assisted heat pump coupled mine backfill body heat storage system (SAHP-MBBHSs) based on TRNSYS simulation software and verifies the accuracy of the backfill heat exchangers (BFHEs) model through experiments. Considering the influence of various external factors on the operating conditions, we investigated the long-term seasonal heat storage/release performance of the BFHEs, focusing on the effects of solar collector area, U-tube spacing, thermal conductivity of backfill materials, and heat storage start/stop time. The results show that reducing the U-tube spacing increases the fluctuation amplitude of the average temperature of the backfill body, with the maximum average fluctuation amplitude difference reaching 16.6°C between the 11th and 15th years. Delaying the onset of thermal storage reduces the storage effectiveness of the U-BFHEs, while increasing the heat release effectiveness. During the thermal storage/release interval, heat loss to the surrounding rock does not exceed 4.7%, with the minimal overall impact. The thermal conductivity of the backfill body has the greatest effect on the heat transfer effectiveness of U-BFHEs, increasing from 1 W·m−1·K−1 to 2 W·m−1·K−1 resulting in respective increases of 58.8% and 39.2% in the heat transfer effectiveness during the 15th year of thermal storage/release. The total heat storage-release effectiveness of the U-BFHEs does not exceed 43.7%, indicating significant room for improvement. Utilizing seasonal thermal storage in the backfill body can effectively enhance the heating performance of SAHP-MBBHSs, with the maximum average APF and HSPF values reaching 3.85 and 5.43, respectively, during the 11th–15th years of operation, maintaining high efficiency even after long-term operation.