The infinite line source (ILS) theory for soil thermal property determination with heat pulse (HP) sensors is simple and widely-used, but ignores the finite probe radius (r) and heat capacity (C_p). The cylindrical-perfect-conductors (CPC) theory, which accounts for r and C_p by using the identical-cylindrical-perfect-conductors (ICPC) or the dissimilar-cylindrical-perfect-conductors (DCPC) approaches, can be applied to estimate soil thermal property values with improved accuracy. In this study, the ILS and CPC theories were evaluated, and the finite r and C_p effects were quantified using numerical simulations and laboratory measurements with a large HP sensor of dissimilar probes. The errors due to finite probe properties were saturation dependent: Dry soils had a 14% reduction in the maximum temperature rise of the HP signal, while only slight temperature differences occurred in wet sandy soils. The finite probe effects were minor on ICPC- and DCPC-thermal property values with relative errors generally less than 5%, but the absolute values of relative errors for dry soils were greater than 6%. Errors caused by ignoring the finite probe effects changed linearly with the ratio of soil heat capacity (C) versus C of the heating and sensing probes. The dissimilar probe r had negligible effect on HP signals and thermal property estimates with the specific sensor used in this study. The effects of finite probe size and properties should be considered in HP sensor design. The CPC theory is recommended for estimating soil thermal properties with large HP sensors.

中文翻译：

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无限线源和圆柱完美导体理论在大传感器热脉冲测量中的应用

使用热脉冲 (HP) 传感器确定土壤热特性的无限线源 (ILS) 理论简单且应用广泛，但忽略了有限探针半径 ( r ) 和热容量 ( C _p )。圆柱完美导体 (CPC) 理论通过使用相同圆柱完美导体 (ICPC) 或不同圆柱完美导体 (DCPC) 方法来解释r和C _p，可用于估计精度更高的土壤热特性值。本研究评估了 ILS 和 CPC 理论，有限r和C _p使用由不同探针组成的大型 HP 传感器，使用数值模拟和实验室测量来量化影响。由于有限探头特性导致的误差取决于饱和度：干燥土壤的 HP 信号的最大温升降低了 14%，而潮湿的沙质土壤中仅出现轻微的温差。有限探针对ICPC-和DCPC-热性能值的影响较小，相对误差一般小于5%，但干土的相对误差绝对值大于6%。忽略有限探针效应导致的误差随着土壤热容量 ( C ) 与加热和传感探针的C的比率线性变化。异种探针r本研究中使用的特定传感器对 HP 信号和热特性估计的影响可以忽略不计。在 HP 传感器设计中应考虑有限探头尺寸和特性的影响。推荐使用 CPC 理论来估计具有大型 HP 传感器的土壤热特性。