Thermal conductivity investigations of granular and powdered silica aerogels at different temperatures and pressures
Thermal conductivity investigations of granular and powdered silica aerogels at different temperatures and pressures
复制标题
不同温度和压力下颗粒状和粉末状二氧化硅气凝胶的导热系数研究
DOI：
10.1016/j.enbuild.2016.03.008
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发表时间：
2016-04
影响因子：
6.7
通讯作者：
Yang Yongping
中科院分区：
文献类型：
--
作者：
Wei Gaosheng;Wang Lixin;Xu Chao;Du Xiaoze;Yang Yongping
本文介绍了用瞬态热剥离法（THS）测定粉末和颗粒状二氧化硅气凝胶热导率的实验。设计了一种用于THS法测量不同温度和压力下热导率的真空炉。采用低温氮气吸附法测定了两种样品的比表面积和平均中孔直径。结果表明，粉末状样品的导热系数仅在压力小于20 Pa时达到恒定值，而颗粒状样品的导热系数在压力小于3 Pa时由于大孔效应而达到恒定值。随着气压的降低，样品的热导率呈现出相似的变化规律，当p> 1000 Pa时，热导率先缓慢下降，当p < 1000 Pa时，热导率又加速下降。所测量的样品的热导率随着温度的升高而明显增加，表明具有较大大孔的二氧化硅气凝胶材料在升高的温度下表现出比整体二氧化硅气凝胶材料更高的热导率。
This paper describes the experimental determination of thermal conductivity of powdered and granular silica aerogels using the transient hot-strip (THS) method. A vacuum furnace was designed for the THS method for measuring thermal conductivity at different temperatures and pressures. The specific surface area and average mesopore diameter of the two samples were also measured by cryogenic nitrogen adsorption method. The results show that the thermal conductivity of the powdered sample reached a constant only when the pressure was less than 20 Pa, while the thermal conductivity of the granular sample became constant when the pressure was less than 3 Pa due to the macropore effect. The measured samples demonstrated similar patterns in thermal conductivity as gas pressure decreased, with the thermal conductivity first declining slowly whenp> 1000 Pa, than with an accelerated decline oncep< 1000 Pa. The thermal conductivity of the measured samples distinctly increased with elevation of temperature, indicating that silica aerogel materials with larger macropores exhibit higher thermal conductivity than monolithic silica aerogel materials at elevated temperatures.
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DOI：
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