Abstract

Effective ground thermal properties are the most important parameters in the design of borehole heat exchanger (BHE), which are usually can be obtained by thermal response test (TRT). They’re often vary with depth and influenced by heat injection. This paper presents a method combining TRT and thermal recovery test (TrT) to evaluate the ground thermal properties. The TRT and TrT conducted on a single U-pipe BHE by the TRT rig and two measurement lines each with ten three-wire Pt-100 temperature sensors. Thermal conductivity and borehole thermal resistance at different depths were inferred by the infinite line source model (ILSM) during the TRT while by combining the ILSM with the superposition principle and parameter estimation method during the TrT. Results reveal that, although the heat injection rate varies significantly in the TRT period, the average effective ground thermal conductivity and borehole thermal resistance inferred from the TRT are similar to those inferred from the TrT. However, the results at different depths show great variability and correspond to groundwater and geological information. In addition, TrT results showed that acceptable results (within 5% error) could be obtained for 22 hours in a TrT.

中文翻译：

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基于 U 型管埋管换热器热响应和热恢复试验的热物理和传热特性

摘要

有效地热性能是钻孔换热器（BHE）设计中最重要的参数，通常可以通过热响应试验（TRT）获得。它们通常随深度而变化，并受热注入的影响。本文提出了一种结合 TRT 和热恢复试验 (TrT) 的方法来评估地热特性。TRT 和 TrT 通过 TRT 钻机和两条测量线在单个 U 形管道 BHE 上进行，每条测量线各有十个三线 Pt-100 温度传感器。在TRT期间，通过无限线源模型（ILSM）将无限线源模型（ILSM）与TrT期间的叠加原理和参数估计方法相结合，推断出不同深度的导热系数和钻孔热阻。结果表明，虽然热注入率在 TRT 期间变化很大，从 TRT 推断的平均有效地面热导率和钻孔热阻与从 TrT 推断的相似。然而，不同深度的结果显示出很大的变异性，并且与地下水和地质信息相对应。此外，TrT 结果表明，在 TrT 中持续 22 小时可以获得可接受的结果（误差在 5% 以内）。