土壤导热率测定及其计算模型的对比分析

土壤导热率是重要的热参数之一,为了获得预测导热率的准确方法,该文对比分析了确定土壤导热率的热脉冲直接测定法和模型间接推求法。根据热脉冲原理在相同体积质量下,测定了不同质地和含水率土壤的导热率值。结果表明在相同含水率条件下,砂粒含量越高,土壤的导热率越大,土壤导热能力越强。利用Horton经验公式对实测值进行了拟合,结果显示Horton经验模型基本可以反映土壤导热率变化特征,并得到了Horton公式经验系数。利用实测值与Campbell模型计算值进行了比较,结果显示Campbell模型计算结果偏差较大,并对其进行了修正。并且用实测值与Johansen模型及其2种改进模型(Coté-Konrad模型和Lu-Ren模型)的计算值进行了对比分析,结果表明Johansen模型计算结果与实测值偏差较大,2种改进型模型的计算结果与实测值更接近。该研究表明土壤导热率可以利用土壤质地、含水率、孔隙度和体积质量进行计算,3种理论模型的计算值与实测值的相关系数均值分别为:0.643、0.937、0.943,推荐使用Coté-Konrad模型和Lu-Ren模型计算土壤导热率,Lu-Ren模型比Coté-Konrad模型的适用范围更广。

Soil thermal properties determination and prediction model comparison

The thermal conductivity is one of the important thermal parameters. In order to get the method for accurately forecasting the thermal conductivity of soils, the heat-pulse direct measuring method and indirect calculation method were compared. According to the principle of heat-pulse, the thermal conductivity of soils with different textures and moisture in the same soil bulk density were measured. The results showed that, under the same moisture, the soil thermal conductivity increased with the sand content rise. Horton equation was used to fit the measured values. The results indicated that the Horton equation may be used to describe the relationship between thermal conductivity and water content, and the parameters in Horton equation were given. Campbell empirical formula of thermal conductivity was used to calculate the thermal conductivity. The results show that there was a large difference between the calculated and measured values. Johansen model and two improved models were used to calculate the thermal conductivity. The results showed that there was a deviation between Johansen model calculated values and measured values, and the results from two improved models were more consistent with measured values. The research indicated that soil thermal conductivity can be calculated by soil texture, water content, soil porosity and bulk density. The correlation coefficients of calculated values from C?té-Konrad model and Lu-Ren model with measured values were 0.643, 0.937 and 0.943, respectively. The two improved models are recommend for calculating soil thermal conductivity, and the application scope of Lu-Ren model is wider than that of C?té-Konrad model.