Transparent evacuated insulation

Journal Article · Sun Nov 01 04:00:00 EST 1992 · Solar Energy (Journal of Solar Energy Science and Engineering); (United States)

DOI:https://doi.org/10.1016/0038-092X(92)90106-K· OSTI ID:7058834

Collins, R E; Fischer-Cripps, A C; Tang, J Z ^[1]

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1. Univ. of Sydney (Australia)

Transparent evacuated insulation utilizes the same operating principles as the Dewar flask - gas conduction and convection are essentially eliminated by the evacuated space, and radiative heat transport is small because of internal low emittance coatings. These insulating structures consist of two flat sheets of glass with a hermetic edge seal. An array of support pillars is necessary to maintain the separation of the glass sheets under the influence of atmospheric pressure. The extensive literature on transparent evacuated insulation is reviewed. The design of these devices involves trade-offs between the heat flow through the pillars, and the mechanical stresses. A design methodology for determining the dimensions of the pillar array is developed. An analytic method is described for calculating the stresses and bending produced by a temperature difference across the structure. The results are in reasonable agreement with experimental measurements. The stresses within the structure are shown to be less than conventionally accepted levels over a wider range of operating conditions. Many samples of transparent evacuated insulation have been built and tested in which the heat transport through the evacuated space is due entirely to radiation, to the limit of resolution of the measuring device (0.2 W m{sup {minus}2}K{sup {minus}1}). No increase in heat transport has been observed over a period of 18 months. Much higher accuracy measurements have commenced. It appears likely that transparent evacuated insulation will achieve mid-plane insulating values of 0.6 W m{sup {minus}2}K{sup {minus}1}, and possibly somewhat lower.

• OSTI ID: 7058834
• Journal Information: Solar Energy (Journal of Solar Energy Science and Engineering); (United States), Journal Name: Solar Energy (Journal of Solar Energy Science and Engineering); (United States) Vol. 49:5; ISSN SRENA; ISSN 0038-092X
• Country of Publication: United States
• Language: English

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