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<title>The Infrared Emittance Of Semi-Transparent Materials Measured At Cold Temperatures</title>

1984; SPIE; Volume: 0446; Linguagem: Inglês

10.1117/12.939160

1996-756X

Stephen Marshall,

Thermography and Photoacoustic Techniques

The infrared emittance of semi-transparent glazing materials used in passive solar building construction was measured over the temperature range -5.6°C to +15°C at 2 - 5.6 μm wavelength. A table of measured apparent emittance values is presented. Absolute values of emittance are not provided due to the conclusion that no adequate model describing three-dimensional emittance in terms of thickness, rectilinear transmittance, and broadband detector sensitivity has yet been formulated. A rough rule-of-thumb for thermographers appears to be that a high emittance value can be assumed for most thick sheets of these materials but the emittance of thin films drops rapidly below a certain critical thickness.