Page 192 - Mechanical Engineers' Handbook (Volume 4)
P. 192
3 Radiation Heat Transfer 181
Figure 19 Hemispherical spectral emissive power of a blackbody for various temperatures.
indicate averaging over the total wavelength spectrum). For a given wavelength the spectral
hemispherical emissivity of a real surface is defined as
e /e b
where e is the hemispherical emissive power of the real surface and e is that of a blackbody
b
at the same temperature.
Spectral irradiation, G , (W/m m), is defined as the rate at which radiation is incident
2
upon a surface per unit area of the surface, per unit wavelength about the wavelength , and
encompasses the incident radiation from all directions.
Spectral hemispherical reflectivity, is defined as the radiant energy reflected per unit
time, per unit area of the surface, per unit wavelength/G .
