An analytical model for combined radiative and conductive heat transfer in fiber-loaded silica aerogels

Zhao, Junjie; Duan, Yuan-Yuan; Wang, Xiaodong; Wang, Bu‐Xuan

doi:10.1016/j.jnoncrysol.2012.02.037

Cited by 68 publications

(24 citation statements)

References 34 publications

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“…However, it should be mentioned that carbon black (which was not taken into consideration during the chemical analysis) or C compounds are also loaded into the aerogels as opacifiers to reduce the radiative heat transfer [40]. Therefore, in this area, our results are incomplete, and the possible role of impurities cannot be unambiguously identified.…”

Section: Thermal Conductivity Testmentioning

confidence: 93%

“…One of the important parameters is the thickness of the fibres loaded into aerogels. It was shown for amorphous SiO 2 glass fibres that the optimum thickness for the best thermal insulation performance is 4-8 μm [40]. It should be noted that the thickness of the fibres in sample A differs greatly from those of the samples B and Pyrogel® and only the diameter of sample A fibres is clearly outside its quoted thickness range.…”

Section: Thermal Conductivity Testmentioning

confidence: 96%

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Aerogel insulation materials for industrial installation: properties and structure of new factory-made products

Miros

Psiuk

Szpikowska‐Sroka

2017

J Sol-Gel Sci Technol

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In this article the comparisons of two new factory-made Chinese aerogel products with the Pyrogel® product, all available on the market, are presented. The aerogel products are in a flexible blanket form and all products are dedicated for high temperature applications. The properties of the samples such as their dimension stability, water vapour transmission and water absorption are also described. Additionally the microstructure and chemical composition of the products are analysed using SEM/ EDS (scanning electron microscopy coupled with X-ray energy-dispersive spectroscopy). The differences in the maximum service temperature are presented. The internal self-heating of the aerogel samples is described and is compared to a similar effect observed in mineral wool samples. The results in the change of the thermal properties in a wide range of temperatures (+ 10-600°C) are shown. The obtained results are correlated with the mineral wool data. The correlation shows an advantage in a highefficiency thermal performance of aerogel products compared to other insulation materials at high temperatures. Graphical Abstract

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Section: Thermal Conductivity Testmentioning

confidence: 93%

Section: Thermal Conductivity Testmentioning

confidence: 96%

Aerogel insulation materials for industrial installation: properties and structure of new factory-made products

Miros

Psiuk

Szpikowska‐Sroka

2017

J Sol-Gel Sci Technol

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“…2. This cubic array was first recommended by Zeng et al [27], and adopted by others for their heat transfer analyses [14,25,[28][29][30]. In the figure, D is the side length of the column, d is the diameter of the spherical nanoparticles, a is the contact diameter between two nanospheres, and n is the number of nanospheres in each column.…”

Section: Correlations Between S S and φ And Nanoporous Structuresmentioning

confidence: 99%

Analysis of Gas Molecule Mean Free Path and Gaseous Thermal Conductivity in Confined Nanoporous Structures

et al. 2015

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This study comprehensively analyzes the mean free path of gas molecules and gaseous thermal conductivity in confined nanoporous structures through a wide range of temperatures and pressures. A simplified unit cell cubic array structure of nanospheres is used to correlate microstructure features with specific surface area and density of nanoporous materials. Zeng's model is used to describe the mean free path of the gas molecules and the gaseous thermal conductivity in confined nanoporous structures, and experimental gaseous thermal conductivity data from the literature is used to validate the model. The results show that a material's nanoporous structure features are directly related to specific surface area and density. The mean free path of gas molecules in a confined nanoporous structure decreases with increasing specific surface area and density. Thus, nanoporous materials with a relatively high specific surface area and a higher density are more favorable for confining gaseous thermal conductivity in nanopores. This work shows that p = 10 4 Pa and 10 6 Pa are two characteristic pressures at ambient temperatures for the investigated silica aerogel materials. When p < 10 4 Pa, the mean free path of the gas molecules remains constant with varying pressure, while gaseous thermal conductivity approaches zero due to the restrictive effect of the nanoporous structure and the diluted gas molecules. When p > 10 6 Pa, the limiting effect of the nanoporous structure on the movement of gas molecules can be ignored, and so the mean free path of gas molecules in the nanoporous material approaches the mean free path of gas molecules in free space, B Gaosheng Wei 123 Int J Thermophys while the gaseous thermal conductivity approaches the gaseous thermal conductivity in free space. As temperature increases, there exists a maximum value for gaseous thermal conductivity in confined nanoporous materials, but this maximum increases as pressure increases. The maximum gaseous thermal conductivity for the material is also determined in the paper.

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“…Today, one of the most focusing areas is the modeling of the thermal behavior of granular-and fiber-based silica aerogel and its composites [9][10][11][12][13]. Despite all these efforts, silica aerogel has been applied only for scientific motives in the aerospace industry.…”

Section: Introductionmentioning

confidence: 99%

Flexible and Transparent Silica Aerogels: An Overview

Parale¹,

Lee²,

Park³

2017

J. Korean Ceram. Soc

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Aerogels are highly porous structures prepared via a sol-gel process and supercritical drying technology. Among the classes of aerogels, silica aerogel exhibits the most remarkable physical properties, possessing lower density, thermal conductivity, refractive index, and dielectric constant than any solids. Its acoustical property is such that it can absorb the sound waves reducing speed to 100 m/s compared to 332 m/s for air. However, when it comes to commercialization, the result is not as expected. It seems that mass production, particularly in the aerospace industry, has dawdled behind. This paper highlights the evolution of aerogels in general and discusses the functions and significances of silica aerogel in previous astronautical applications. Future outer-space applications have been proposed as per the current research trend. Finally, the implementation of conventional silica aerogel in aeronautics is argued with an alternative known as Maerogel.

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An analytical model for combined radiative and conductive heat transfer in fiber-loaded silica aerogels

Cited by 68 publications

References 34 publications

Aerogel insulation materials for industrial installation: properties and structure of new factory-made products

Aerogel insulation materials for industrial installation: properties and structure of new factory-made products

Analysis of Gas Molecule Mean Free Path and Gaseous Thermal Conductivity in Confined Nanoporous Structures

Flexible and Transparent Silica Aerogels: An Overview

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