Pore Size Distribution and Apparent Gas Thermal Conductivity of Silica Aerogel

1994 ◽  
Vol 116 (3) ◽  
pp. 756-759 ◽  
Author(s):  
S. Q. Zeng ◽  
A. J. Hunt ◽  
W. Cao ◽  
R. Greif
Keyword(s):  
Thermal Conductivity ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Silica Aerogel

Thermal Conductivity of Sol-Gel Bonded Castables

2008 ◽  
Vol 368-372 ◽  
pp. 1146-1148
Author(s):  
Feng Cao ◽  
C.Y. Wang ◽  
P.S. Tang ◽  
C.Y. Lu ◽  
H.F. Chen ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Glassy Phase ◽  
Size Structure ◽  
Sol Gel ◽  
Refractory Castables ◽  
Silica Alumina ◽  
Alumina Sol

The silica-alumina sol bonding agent, prepared by the sol gel route from ethyl silicate and aluminium isopropanol, was utilized in the refractory castables. The influence of structure on the heat transfer has been investigated using different sorts of refractory matrix. The results indicated that the heat conductivity of sol-gel bonded castables was considerably affected by their structure. The phase composition of matrix, porosity, pore size distribution and pore size structure were the most important factors. Thermal conductivity has been measured from the ambient temperature up to 1250 °C. The influence of crystalline phases and the glassy phase formation and the influence of the pore size distribution on the thermal conductivity were also described in this work.

Study on the Effective Thermal Conductivity of Macro, Mirco and Nano Porous Materials in the Light of the Knudsen Conduction/Radiation Coupling Effect

2010 ◽  
Author(s):  
Ulrich Gross ◽  
Khaled Raed
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Pore Size Distribution ◽  
Porous Materials ◽  
Pore Size ◽  
Effective Thermal Conductivity ◽  
Size Distribution ◽  
Solid Matrix ◽  
Porous System ◽  
Gas Atmosphere

Thermal transport phenomena in porous media are characterized by conduction through solid matrix and filling gas, and also by radiation. The gas is dispersed in the porous system depending on the pore size distribution. In each pore, the gas contributes to the heat transfer between the pore surfaces. This effect is strongly influenced by pore size, gas atmosphere, accommodation coefficient and other factors. A recent publication of the present authors focused on modeling the change of the effective thermal conductivity when the gas atmosphere is changed. In the current contribution, the effect of pore size distribution on heat transfer in macro, micro, and nano insulation materials is presented. Samples were chosen from five different highly porous materials with different pore size distribution within the macro, micro, and nano classes. Porosity and pore size distribution of the samples were chosen to get a clear characterization of the materials. The effective thermal conductivity was measured by applying the radial heat flow method at temperatures up to 1000 °C. Evaluating Knudsen effect from the pore size distribution alone does not give plausible explanation for the measured thermal conductivity. However, it is important to consider the kind of connections between the pores. In case of nano materials, the radiation effect proves to be strongly dependent on the Knudsen number.

Effect of Burning-Out Materials on the Properties of Synthesized Microporous Mullite

2012 ◽  
Vol 151 ◽  
pp. 271-274
Author(s):  
Yu Bao Bi ◽  
Hui Fang Wang ◽  
Wei Lu
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Microporous Structure ◽  
Volume Stability ◽  
Temperature Environment ◽  
High Temperature Environment ◽  
Industrial Alumina

Mullite can be prepared as lightweight refractories for its low thermal conductivity, advanced volume stability at high temperature environment. Using industrial alumina and nature silica powders as starting materials, the mullite aggregates with microporous structure were synthesized by adding some burning-out materials as pore forming agents. The effects of burning-out materials on the pore size distribution, mullite contents and microstructure of microporous mullite have been investigated. The results show that the effects on the mullite contents and microstructure of microporous mullite are significant. All the burning-out materials have a similar effect for the pore size distribution.

scholarly journals Influence of Pore Size Variation on Thermal Conductivity of Open-Porous Foams

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2017 ◽  
Author(s):  
Jakub Skibinski ◽  
Karol Cwieka ◽  
Samih Haj Ibrahim ◽  
Tomasz Wejrzanowski
Keyword(s):  
Thermal Conductivity ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Structural Parameters ◽  
Size Variation ◽  
Design Procedure ◽  
Open Cell ◽  
Open Cell Foam ◽  
Analytical Formulas

This study addresses the influence of pore size variation on the effective thermal conductivity of open-cell foam structures. Numerical design procedure which renders it possible to control chosen structural parameters has been developed based on characterization of commercially available open-cell copper foams. Open-porous materials with various pore size distribution were numerically designed using the Laguerre–Voronoi Tessellations procedure. Heat transfer through an isolated structure was simulated with the finite element method. The results reveal that thermal conductivity is strongly related to porosity, which is in agreement with the literature. The influence of pore size distribution has also been observed and compared with analytical formulas proposed in the literature.

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