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Thermal (2-5.6 µm) Emittance Of Diathermanous Materials As A Function Of Optical Depth, Critical Angle And Temperature
Author(s): R. H. Munis; S. J. Marshall
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Paper Abstract

Thermal (2.0 μ - 5.6 μm) measurements of the normal emittance (EN) of several diathermanous materials were made at 15.2°C, 4.9°C and -5.6°C. Calculations of the total hemis-pherical emittance (EH) were made from EN and plotted against the optical depth (YΔλx). A comparison of these data with a model proposed by Gardon indicates that at near-ambient temperatures they agree very closely. It has been observed that EN > EH by ≈ 5% for both weakly and strongly absorbing materials. This is attributable to phase differences in the multiply reflected internal radiation attempting to exit the specimen throughout π steradians. Other radiation properties of the materials, i.e. diffuse transmittance (TD), absorption coefficient yΔx, and absorption index k were calculated.

Paper Details

Date Published: 21 January 1985
PDF: 13 pages
Proc. SPIE 0510, Infrared Technology X, (21 January 1985); doi: 10.1117/12.945025
Show Author Affiliations
R. H. Munis, U.S. Army Cold Regions Research and Engineering Laboratory (United States)
S. J. Marshall, U.S. Army Cold Regions Research and Engineering Laboratory (United States)

Published in SPIE Proceedings Vol. 0510:
Infrared Technology X
Richard A. Mollicone; Irving J. Spiro, Editor(s)

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