土壤热通量板测量误差及Philip修正公式的适用性

Measuring Error of Soil Heat Flux Plate and Applicability of Philip’s Equation for Modification

土壤热通量的测量是地表热量平衡研究中重要的一部分。测量土壤热通量有很多种方法,其中热通量板法简单易行但准确度无法判定。采用计算机模拟与室内实验相结合的方法,研究土壤热通量板测量误差及影响因素;将土壤作为均匀介质,将热通量板作为复合材料,研究复合材料在均匀介质中对温度场和热流分布的影响。此外,本文还对Philip在1961年提出的修正公式的效果进行了分析。结果表明,当土壤与热通量板的热导率接近时,热通量的测量误差较小;Philip修正公式在瞬态条件下的适用性较差。本研究表明,由于热通量板与土壤二者热导率的差异,热流在板边缘处会扭曲,从而导致热通量测量误差;由于Philip公式在推导过程中存在简化运算的处理,在土壤温度随时间波动的情况下,校正值与理论值间仍存在差异的现象,表明该公式的适用范围有限。

【Objective】Measurement of soil heat flux is pivotal to researches on budgeting of surface heat.To measure soil heat flux,there are several ways,one of which is the heat flux plate method,simple and easy to handle,but unpredictable in accuracy.【Method】In this study,an indoor experiment was carried out in combination with computer simulation to determine errors of the measurement with the soil heat flux plate method and explore its influencing factors.In this paper,with soil deemed as homogenous medium and the heat flux plate as composite material,influences of the composite material on temperature field of and heat flux distribution in the homogenous medium.In addition,analysis was done of applicability of the modificatiton equation Philip put forth in 1961.【Result】Results show that when the soil and the plate is quite approximate in heat conductivity measurement error of the method is low and Philip’s equation is relatively low in applicability under transient conditions.【Conclusion】The study shows that due to difference in thermal conductivity between the heat flux plate and the soil,the heat flow will distort at the edge of the plate,thus leading to occurrence of errors in the measurement.As Philip’s equation simplifies computation in the derivation process,difference is still found between calibrated value and theoretical value when soil temperature varies with time,which indicates that its application is limited in range.