土壤热导率的温度效应试验和预测研究

Measurement and prediction of temperature effects of thermal conductivity of soils

目前国际上对于高温下土壤的完整热导率数据极其缺乏,通过KD2 Pro测试了粉砂质黏壤土和细砂在较宽广温度(5℃～88℃)和含水率范围内的热导率。测试结果表明,由于水蒸气的凝结和蒸发产生的潜热传输效应,在88℃下热导率最高可达5℃时的3～4倍,热导率随含水率的变化存在明显的临界含水率(依赖于颗粒组成)。对基于de Vries假设的de V-1和Campbell理论模型的验证和对比表明,参考文献中的一些参数及其获取方法的适用性需要改进,修正后的模型基本能较好地预测不同温度下热导率的变化(RMSE<30%),且温度越接近40℃误差越小,粉砂质黏壤土在高温下(58℃～88℃)的θAWC～θPWP区间建议乘以传质增强因子ζ(ζ=2.5)。模型均较为复杂,有待于在此基础上进一步建立易用的经验性模型。

Currently,there is an extreme deficiency of complete data of thermal conductivity of soils under high temperature around the world,tests are thus conducted through KD2 Pro on the silty clay loam and fine sand within a wide range of temperatures（5℃～88℃） and water contents.The results indicate that the thermal conductivity under 88℃ is 3 or 4 times as high as that under 5℃ due to the latent heat transfer effect caused by condensation and evaporation of vapor.The critical water content,which depends on texture,exists as thermal conductivity changes with the water content.According to the verification and comparison of de V-1 and Campbell theoretical models from de Vries＇s hypothesis,improvements are needed on some parameters and the applicability of achieving them in the references.However,the modified models can comparatively better predict the change of the thermal conductivity under different temperatures（RMSE30%）.The closer to 40℃,the lower the error.It is suggested that a mass transfer enhancement factor of ζ2.5 should be multiplied under 58℃～88℃ within θAWC～θPWP for silty clay loam.Judged by the complexity of these two models,the more convenient empirical models are expected to be established based on this foundation.