The thermal conductivity of silica aerogel developed in this research program was measured using the transient hot-wire technique. The thermal conductivity of monolithic samples drops significantly from 9.3 mW/m · K to 3.2 mW/m · K with modest pressure reduction from 1 atm to 0.1 atm. The same aerogel in granular form has a thermal conductivity of 15.0 mW/m · K at ambient gas pressure with a modest compression applied to compact the granules and reduce the air void sizes. Radiation heat transfer in the hot-wire test may not be representative of its contribution in large scale applications. Measurements of the monochromatic extinction coefficient over the wavelengths of interest resulted in a Rosseland mean extinction coefficient of 2400 m−1 at 300 K. The small thermal penetration distance during the hot-wire measurements suggest that in actual use radiation could contribute approximately 2.5 mW/m · K with a possible upper limit of 3.0 mW/m · K to the effective thermal conductivity over that measured using the transient hot-wire method.
Thermal Properties of Silica Aerogel Formula
Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received June 28, 2013; final manuscript received October 3, 2014; published online April 21, 2015. Assoc. Editor: Patrick E. Phelan.
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Cohen, E., and Glicksman, L. (August 1, 2015). "Thermal Properties of Silica Aerogel Formula." ASME. J. Heat Transfer. August 2015; 137(8): 081601. https://doi.org/10.1115/1.4028901
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