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Research Papers: Conduction

Gaseous Conductivity Study on Silica Aerogel and Its Composite Insulation Materials

[+] Author and Article Information
Gaosheng Wei1

 School of Energy and Power Engineering, Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education, North China Electric Power University, Beijing 102206, Chinagaoshengw@126.com

Yusong Liu

 Energy Department of Beijing Sustainable Development Centre, Beijing 100083, Chinalyscare163@163.com

Xiaoze Du

 School of Energy and Power Engineering, Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education, North China Electric Power University, Beijing 102206, Chinaduxz@ncepu.edu.cn

Xinxin Zhang

 Department of Thermal Engineering, University of Science and Technology Beijing, Beijing 100083, Chinaxxzhang@ustb.edu.cn

1

Current address: School of Energy and Power Engineering, North China Electric Power University, Beijing 102206, China.

J. Heat Transfer 134(4), 041301 (Feb 13, 2012) (5 pages) doi:10.1115/1.4004170 History: Received August 23, 2010; Revised May 03, 2011; Published February 13, 2012; Online February 13, 2012

This paper presents a theoretical and experimental study on gaseous conductivity of silica aerogel and composite insulation materials. First, the insulation material samples (including silica aerogel, xonotlite-type calcium silicate, xonotlite-aerogel composite, and ceramic fiber-aerogel composite) were prepared. Next, the gaseous conductivities of the prepared samples were measured from 0.045 Pa to atmospheric pressure using the transient hot-strip (THS) method. The gaseous conductivity expressions obtained based on the kinetic theory were then compared with the experimental results. It is shown that the gaseous conductivity of both xonotlite-type calcium silicate and silica aerogel decreases significantly with decreasing pressure. The gaseous conductivities of xonotlite-type calcium silicate and silica aerogel reach zero at about 100 Pa and 104 Pa, respectively. The theoretical gaseous conductivity expressions match well with the experimental results of xonotlite-type calcium silicate and silica aerogel but not with the experimental results for the composite insulation materials. This mismatch indicates that the aerogel does not totally fill the original interspace of the xonotlite-type calcium silicate and ceramic fiber in the two kinds of composite insulation materials.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 5

Pressure dependence of gaseous conductivity in the composite insulation materials

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Figure 4

Pressure dependence of gaseous conductivity in silica aerogel

Grahic Jump Location
Figure 3

Pressure dependence of gaseous conductivity in xonotlite-type calcium silicate

Grahic Jump Location
Figure 2

Picture of the arrangement of THS apparatus in a vacuum system

Grahic Jump Location
Figure 1

Schematic illustration of transient hot strip setup

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