Thermodynamics HW Solutions 879

Thermodynamics HW Solutions 879 - Chapter 11 Fundamentals...

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Unformatted text preview: Chapter 11 Fundamentals of Thermal Radiation Radiation Properties 11-36C The emissivity is the ratio of the radiation emitted by the surface to the radiation emitted by a blackbody at the same temperature. The fraction of radiation absorbed by the surface is called the absorptivity , ( ) ( ) ( ) T E T E T b = and = = absorbed radiation incident radiation G G abs When the surface temperature is equal to the temperature of the source of radiation, the total hemispherical emissivity of a surface at temperature is equal to its total hemispherical absorptivity for radiation coming from a blackbody at the same temperature T ( ) ( ) T T = . 11-37C The fraction of irradiation reflected by the surface is called reflectivity and the fraction transmitted is called the transmissivity = = G G G G ref tr and Surfaces are assumed to reflect in a perfectly spectral or diffuse manner for simplicity. In spectral (or mirror like) reflection, the angle of reflection equals the angle of incidence of the radiation beam. In diffuse mirror like) reflection, the angle of reflection equals the angle of incidence of the radiation beam....
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