水分含量对颗粒型含湿多孔介质导热系数的影响及机理

The Influence Mechanism of Moisture Content on Thermal Conductivity of Unsaturated Wet Porous Medium

本文用玻璃珠模拟堆积型多孔介质,用Hotdjsk热常数分析仪对不同含湿率下玻璃珠堆积颗粒的导热系数进行测量,并利用CCD结合体式显微镜观察不同含湿率下试样孔隙内的水分形态及颗粒聚集状态,研究分析水分含量、水分形态,颗粒聚集状态对堆积型多孔介质导热系数的影响及机理。实验结果表明;试样的导热系数随含湿率的增大呈非单调递增趋势.不同含湿率下堆积型多孔介质孔隙内水分形态不同,其对颗粒的作用不同,颗粒间出现聚集,从而导致颗粒间距离发生变化,进而表观体积变化。水分含量、水分形态、颗粒间间距的变化均会影响介质的导热系数大小,介质导热系数的变化趋势是由这些影响因素综合决定的。

A hotdisk thermal constant analyzer is used to measure thermal conductivity of porous media, unconsolidated glass beads, and use CCD combined with a stereo microscope to observe the water morphology and particle aggregation state in sample with different moisture contents. The experimental results show that： the thermal conductivity of sample non-monotonically increases with moisture content increasing. Different water morphologies exist in pores of unconsolidated porous medium with different moisture contents and has different forces on particles, so particles aggregate in different scales and distances among particles, i.e. pore size, changes with different moisture contents. As a result, the apparent sample volume changes with moisture content varying. Moisture content, water morphology and pore size will comprehensively affect the thermal conductivity of porous media.