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Theses

Transferts conductifs dans des aérogels de silice, du milieu nanoporeux autosimilaire aux empilements granulaires

Abstract : Silica aerogels are nanoporous materials with extraordinary physical properties. Their thermal performance may be interesting for the building superinsulation. A detailed study of heat conduction through these media has been performed numerically and experimentally.

Monolithic aerogels are autosimilar materials constituted of air in the nanopores and of tortuous solid skeleton. Heat conduction modeling with the heat diffusion equation in two dimensions has been realized using original geometries representing the internal structure. Several types of geometries have been tested. The best compromise is achieved by periodic patterns constructed from Von Koch snowflakes which are deterministic fractals.

From the results obtained at the nanopore scale, heat conduction of regular grain packing has been studied at macroscopic scale and in two dimensions. The original approach is based on the analytical calculus of the thermal contact resistance taken into account in the numerical model. A parametric analysis is then realized using a method of experiment plans.

Finally, experiments based on a method of guarded thin hot film are made in order to compare with numerical results for monolithic and granular silica aerogels. The thermal characterization of samples as a function of air pressure in the pores and of the external force is possible.
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https://tel.archives-ouvertes.fr/tel-00260009
Contributor : Sandra Spagnol <>
Submitted on : Sunday, March 2, 2008 - 5:08:23 PM
Last modification on : Friday, June 26, 2020 - 9:56:02 AM
Long-term archiving on: : Thursday, May 20, 2010 - 7:39:39 PM

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  • HAL Id : tel-00260009, version 1

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Sandra Spagnol. Transferts conductifs dans des aérogels de silice, du milieu nanoporeux autosimilaire aux empilements granulaires. Energie électrique. INSA de Toulouse, 2007. Français. ⟨tel-00260009⟩

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