膨润土热传导性能的温度效应

以高庙子（GMZ07）和美国怀俄明州（MX80）钠基膨润土为研究对象，采用热探针法研究温度对压实膨润土试样热传导性能的影响。在保持干密度和含水率不变的情况下，使用KD2 Pro型热特性分析仪测定不同温度（5～90 ℃）试样的热传导系数，并对部分试样进行压汞试验。试验结果表明：GMZ07和MX80膨润土的热传导系数均随着温度的增大而增大，在90 ℃时最高可达5 ℃的1.2～1.5倍，主要原因是温度引起的水汽潜热传输促进了试样内部的热传导；当试样温度高于60 ℃时，温度对热传导系数的影响较低于60 ℃时更显著；含水率不为0时，两种膨润土热传导系数的温度效应均随干密度的增大而减小；干试样的热传导系数几乎不随温度发生变化，这与水汽潜热传输的强化机制有关。热传导系数温度效应的机制可理解为：热传导系数取决于试样内部可供潜热传输的水分和传热通道数。

Temperature effect on thermal conductivity of bentonites

The temperature effect on thermal conductivity of compacted Gaomiaozi (GMZ07) and Wyoming (MX80) bentonites was investigated using a thermal probe method. Dry densities and water contents of compacted bentonite specimens were kept constant under constant volume conditions, and then measurements of thermal conductivity were conducted over a wide range of temperatures (5°C to 90°C) by KD2 Pro thermal characteristic analyzer. Meanwhile, the mercury intrusion porosimetry (MIP) tests were also performed to observe the pore-size distributions of compacted specimens. The test results show that at the same water content and dry density, the thermal conductivities of GMZ07 and MX80 bentonites increase with increasing the temperature. When the temperature was 90°C, they can reach 1.2 to 1.5 times of the value at 5°C, due to the enhanced latent heat transfer (LHT) of vapor. At specimen temperature is higher than 60°C, the effect of temperature on the thermal conductivity is more significant than that when temperature is under 60°C. For unsaturated specimens, the temperature effect on the thermal conductivity decreases with increasing the dry density. For a dry specimen, the thermal conductivity hardly changes with the temperature, which is related to the enhancement mechanism of the LHT of vapor. The temperature effect on the thermal conductivity can be explained that the more water vapor and heat transfer paths can be used for LHT, the more obvious the temperature effect on the thermal conductivity.