The proper assessment of soil thermal properties, such as thermal conductivity, assumes a particular relevance for the design of Ground Source Heat Pump systems, as it determines the heat transfer and the energy efficiency design. Multiple methods can be used for thermal conductivity estimation, however significant scatters in measurements are often reported when using different (or even the same) methods. This work presents a detailed study of the thermal conductivity and the thermal contact conductance of a reference sand tested in transient conditions, analyzing the effect of several factors, such as the heating time, degree of saturation, soil density, temperature and heat flux intensity, on thermal conductivity measurements for dry state or fully saturated conditions. To avoid measurement errors and heterogeneity effects, only three samples were prepared with different compaction ratios, and systematically tested in dry and fully saturated conditions, under different control variables (temperature, testing time, and injected heat flux). Two analytical methods based on the line source solution were used to estimate soil thermal conductivity and to assess the probe-to-soil thermal contact conductance. Significant relationships were obtained between thermal conductivity and soil state conditions and testing variables, highlighting that a heating time longer than the one usually recommended in the standards is clearly needed. Finally, this study uses measured temperature values to determine the probe-to-soil thermal contact conductance, indicating its relevance in soil thermal conductivity estimation.

对土壤热特性（例如导热系数）的正确评估与地源热泵系统的设计具有特殊的相关性，因为它决定了传热和能效设计。可以使用多种方法来估计热导率，但是当使用不同（甚至相同）方法时，通常会报告测量结果的显着分散。这项工作详细研究了瞬态条件下测试的参考砂的导热系数和接触热导，分析了加热时间、饱和度、土壤密度、温度和热通量强度等几个因素的影响，干燥状态或完全饱和条件下的热导率测量。为了避免测量误差和非均质性影响，仅制备了三个具有不同压实比的样品，并在干燥和完全饱和的条件下，在不同的控制变量（温度、测试时间和注入热通量）下进行了系统测试。使用两种基于线源解决方案的分析方法来估计土壤热导率并评估探头与土壤的热接触电导。热导率与土壤状态条件和测试变量之间存在显着关系，这表明显然需要比标准中通常推荐的时间更长的加热时间。最后，本研究使用测量的温度值来确定探头与土壤的热接触电导，表明其在土壤热导率估计中的相关性。