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Title: Thermal and solar-optical properties of silica aerogel for use in insulated windows

Abstract

Silica aerogel is a porous insulating material that is transport to solar radiation. To understand its insulating performance in a window system, it is necessary to first study component heat transfer paths. Aerogel's absorption coefficient, a measure of the attenuation of radiation heat transfer, was determined over the spectral range 1-200 ..mu..m. Although radiation heat transfer is negligible over much of this region, there is a transmission window between 3-6 ..mu..m. At ambient temperatures, for aerogel thicknesses of 0.5-5.0 cm, radiation heat transfer through an unmodified aerogel window is less than 15% of the total heat flux. For evacuated or high-temperature furnace windows, this contribution can be over 50%. Thermal radiative transfer can be somewhat decreased by allowing the aerogel to absorb moisture, but solar transmission and optical clarity are sacrificed. Absorption of water vapor over time causes irreversible structural changes that increase scattering in the solar spectrum. Aerogel's thermal performance can be improved by replacing the pore gas with one of lower conductivity or by evacuating the aerogel to pressure below 0.1 atm. A hypothetical evacuated aerogel window has a calcuated U-Value of approx. =0.5 W/m/sup 2/-K for a gap spacing of 12.5 mm, which is four times bettermore » than currently available low-emissivity gas-filled units of similar size. 8 refs., 9 figs.« less

Authors:
; ;
Publication Date:
Research Org.:
Lawrence Berkeley Lab., CA (USA)
OSTI Identifier:
5538162
Report Number(s):
LBL-23386; CONF-870711-6
ON: DE88004570
DOE Contract Number:  
AC03-76SF00098
Resource Type:
Conference
Resource Relation:
Conference: Solar '87: 12th national passive solar conference, Portland, OR, USA, 12 Jul 1987; Other Information: Portions of this document are illegible in microfiche products
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; SILICA GEL; ABSORPTION SPECTRA; THERMAL CONDUCTIVITY; WINDOWS; THERMAL INSULATION; ENERGY SPECTRA; EXPERIMENTAL DATA; HEAT TRANSFER; RESIDENTIAL BUILDINGS; ADSORBENTS; BUILDINGS; DATA; ENERGY TRANSFER; INFORMATION; NUMERICAL DATA; OPENINGS; PHYSICAL PROPERTIES; SPECTRA; THERMODYNAMIC PROPERTIES; 140000* - Solar Energy; 320107 - Energy Conservation, Consumption, & Utilization- Building Systems- (1987-)

Citation Formats

Hartmann, J, Rubin, M, and Arasteh, D. Thermal and solar-optical properties of silica aerogel for use in insulated windows. United States: N. p., 1987. Web.
Hartmann, J, Rubin, M, & Arasteh, D. Thermal and solar-optical properties of silica aerogel for use in insulated windows. United States.
Hartmann, J, Rubin, M, and Arasteh, D. Mon . "Thermal and solar-optical properties of silica aerogel for use in insulated windows". United States.
@article{osti_5538162,
title = {Thermal and solar-optical properties of silica aerogel for use in insulated windows},
author = {Hartmann, J and Rubin, M and Arasteh, D},
abstractNote = {Silica aerogel is a porous insulating material that is transport to solar radiation. To understand its insulating performance in a window system, it is necessary to first study component heat transfer paths. Aerogel's absorption coefficient, a measure of the attenuation of radiation heat transfer, was determined over the spectral range 1-200 ..mu..m. Although radiation heat transfer is negligible over much of this region, there is a transmission window between 3-6 ..mu..m. At ambient temperatures, for aerogel thicknesses of 0.5-5.0 cm, radiation heat transfer through an unmodified aerogel window is less than 15% of the total heat flux. For evacuated or high-temperature furnace windows, this contribution can be over 50%. Thermal radiative transfer can be somewhat decreased by allowing the aerogel to absorb moisture, but solar transmission and optical clarity are sacrificed. Absorption of water vapor over time causes irreversible structural changes that increase scattering in the solar spectrum. Aerogel's thermal performance can be improved by replacing the pore gas with one of lower conductivity or by evacuating the aerogel to pressure below 0.1 atm. A hypothetical evacuated aerogel window has a calcuated U-Value of approx. =0.5 W/m/sup 2/-K for a gap spacing of 12.5 mm, which is four times better than currently available low-emissivity gas-filled units of similar size. 8 refs., 9 figs.},
doi = {},
url = {https://www.osti.gov/biblio/5538162}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1987},
month = {6}
}

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