Using Late Time Data Improves the Heat‐Pulse Method for Estimating Soil Thermal Properties with the Pulsed Infinite Line Source Theory
Using Late Time Data Improves the Heat‐Pulse Method for Estimating Soil Thermal Properties with the Pulsed Infinite Line Source Theory
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DOI：
10.2136/vzj2013.01.0011
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发表时间：
2013-11
影响因子：
2.8
通讯作者：
Yili Lu;Yajing Wang;T. Ren
中科院分区：
文献类型：
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作者：
Yili Lu;Yajing Wang;T. Ren
土壤-探头接触电阻和热脉冲探头的有限半径和热容量在热物性估算中会产生很大的误差。在这项研究中，我们证明了从温度随时间变化(ΔT(T))曲线的后期数据估计土壤热性质有效地减少了这些误差。利用脉冲无限长线源(PILS-Complete)、峰值-峰值(PILS-Peak)和晚期(PILS-LATE)3个区间的ΔT(T)数据，采用加权非线性曲线拟合法估算了脉冲无限长线源(PILS)理论下的土壤热性质。对土壤固体比热(Cs)、土壤热性质和土壤水分(θHp)进行了三个试验，以检验这些方法的性能。结果表明，Pils-Complete法和Pils-Peak法分别高估了cs 16.6%和13.0%，Pils-Late法的误差减小到3.2%。用Pils-Late方法测得的土壤导热系数与同圆柱理想导体理论和热流板数据的估计值符合得很好。PILS-LATE方法也有效地减少了土壤热容量的高估和土壤热扩散率的低估。与PILS-Complete法相比，PILS-LATE法将θHP在砂土上的均方根误差从0.039降低到0.021 m~3−3，在粘壤土上从0.032 m~3−3降低到0.018 m~3。因此，利用后期数据提高了HP法测量土壤热物性的精度。
Soil‐probe contact resistance and finite radius and heat capacity of the heat pulse (HP) probe produce significant errors in thermal property estimates. In this study, we demonstrated that estimating soil thermal properties from late‐time data of the temperature change‐by‐time (ΔT(t)) curve reduces these errors effectively. The weighted nonlinear curve fitting method was applied to estimate soil thermal properties following the pulsed infinite line source (PILS) theory using ΔT(t) data from the complete (PILS‐Complete), peak‐time (PILS‐Peak), and late‐time (PILS‐Late) ranges. Three experiments on specific heat of soil solids (cs), soil thermal properties, and soil water content (θHP) were conducted to examine the performance of these approaches. The results showed that the PILS‐Complete and PILS‐Peak methods overestimated cs by 16.6% and 13.0% respectively, and the error from the PILS‐Late method reduced to 3.2%. Soil thermal conductivity measurements from the PILS‐Late method agreed well with those from the identical‐cylindrical‐perfect‐conductors theory and with the estimates from the heat flux plate data. The PILS‐Late method also effectively reduced the overestimation of soil heat capacity and underestimation of soil thermal diffusivity. In comparing to the PILS‐Complete method, the PILS‐Late method reduced the root mean square error (RMSE) of θHP from 0.039 to 0.021 m3 m−3 on a sand soil, and from 0.032 to 0.018 m3 m−3 on a clay loam soil. Thus, using late‐time data improved the accuracy of HP method for measuring soil thermal properties.