In soil thermal energy storage system with high temperature (exceeds 50 °C), the pipe thermal deformation (buckling) can lead to air gap between pipe and soil. During the pipe-soil heat transfer, the gap is actually the thermal resistance. The aim of this study is to investigate the gap between pipe and clay soil, the corresponding heat transfer attenuation and the influence of the initial pipe bending degree. However, the pipe is buried in the soil, the gap is hard to measure. So, the novelty of this work is to put forward the measuring methods of the pipe-soil gap width and the heat transfer attenuation rate from pipe to soil during the heating process. By experiment, the thermal deformation of pipe, the gap width and the heat transfer attenuation rate are analysed. The results indicate that the pipe displacement and the gap width increase with the temperature rise. Correspondingly, the heat transfer attenuation can be found in the gap-side soil area. During the heating process, the heat transfer attenuation rate will decrease with the temperature rise. In comparison, larger pipe bending could get larger thermal deformation, larger gap width and larger heat transfer attenuation rate.

在高温（超过50°C）的土壤蓄热系统中，管道热变形（屈曲）会导致管道与土壤之间产生气隙。在管土传热过程中，间隙实际上是热阻。本研究的目的是研究管道与黏土之间的间隙、相应的传热衰减以及管道初始弯曲度的影响。然而，管道埋在土壤中，缝隙很难测量。因此，本工作的新颖之处在于提出了管-土间隙宽度和加热过程中管-土传热衰减率的测量方法。通过实验分析了管道的热变形、间隙宽度和传热衰减率。结果表明，管道位移和间隙宽度随着温度的升高而增加。相应地，在间隙侧土壤区域可以发现传热衰减。在加热过程中，传热衰减率会随着温度的升高而降低。相比之下，更大的管道弯曲可以获得更大的热变形、更大的间隙宽度和更大的传热衰减率。