class 32 - Real Surfaces Click to edit Master subtitle...

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Click to edit Master subtitle style 8/13/11 Real Surfaces Chapter 12 Sections 12.4,5
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8/13/11 Real surfaces: Correction factor: ) ( ) ( ) ( T E T E T b ε
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8/13/11 Emissivity Surface Emissivity Radiation emitted by a surface may be determined by introducing a property (the emissivity ) that contrasts its emission with the ideal behavior of a blackbody at the same temperature. The definition of the emissivity depends upon one’s interest in resolving directional and/or spectral features of the emitted radiation, in contrast to averages over all directions (hemispherical) and/or wavelengths (total). The spectral , directional emissivity : ( 29 ( 29 ( 29 e b I T T I T λ λ θ λ θ φ ε , , , , , , , , , , The spectral, hemispherical emissivity (a directional average): ( 29 ( 29 ( 29 ( 29 ( 29 2 2 0 0 2 2 0 0 e b b I T d d E T T E T I T d d π θ θ θ φ = / , / , , , , , cos sin , , , , cos sin
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8/13/11 ) ( ) , ( ) , ( ) ( 0 , T E d T E T T b b = λ ε
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8/13/11 Emissivity (cont) Representative spectral variations: Note decreasing ε with increasing for metals and different behavior for nonmetals.
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8/13/11 Emissivity (cont) Representative temperature variations:
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This note was uploaded on 08/13/2011 for the course CHEM 3210 taught by Professor Degrazia during the Fall '10 term at Colorado.

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class 32 - Real Surfaces Click to edit Master subtitle...

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