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Absorptance
Ability of a material to absorb radiant energy From Wikipedia, the free encyclopedia
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In the study of heat transfer, absorptance of the surface of a material is its effectiveness in absorbing radiant energy. It is the ratio of the absorbed to the incident radiant power.[1]
Mathematical definitions
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Hemispherical absorptance
Hemispherical absorptance of a surface, denoted A is defined as[2]
where
- is the radiant flux absorbed by that surface;
- is the radiant flux received by that surface.
Spectral hemispherical absorptance
Spectral hemispherical absorptance in frequency and spectral hemispherical absorptance in wavelength of a surface, denoted Aν and Aλ respectively, are defined as[2]
where
- is the spectral radiant flux in frequency absorbed by that surface;
- is the spectral radiant flux in frequency received by that surface;
- is the spectral radiant flux in wavelength absorbed by that surface;
- is the spectral radiant flux in wavelength received by that surface.
Directional absorptance
Directional absorptance of a surface, denoted AΩ, is defined as[2]
where
- is the radiance absorbed by that surface;
- is the radiance received by that surface.
Spectral directional absorptance
Spectral directional absorptance in frequency and spectral directional absorptance in wavelength of a surface, denoted Aν,Ω and Aλ,Ω respectively, are defined as[2]
where
- is the spectral radiance in frequency absorbed by that surface;
- is the spectral radiance received by that surface;
- is the spectral radiance in wavelength absorbed by that surface;
- is the spectral radiance in wavelength received by that surface.
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Other radiometric coefficients
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References
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