Stefan-Boltzmann Law
Stefan-Boltzmann law states that the total emissive power of a blackbody, Eb, is given by:
Eb = s T4
where s is the stefan-Boltzmann constant and T is the absolute temperature of the blackbody. The value of the Stefan-Boltzmann constant is 5.67x10-8 W/m2 K4 or 3.3063 x 10-15 Btu/s.in2.F4. The spectral variation of blackbody radiation is described by the Planck distribution
. Integrating the Planck distribution law over all wavelengths (l) gives the Stefan-Boltzmann law.
When a blackbody of a surface area (A) is immersed in a medium with ambient temperature Ta, the net rate of heat radiated by the blackbody is given by:
Q
radiation = s A ( T
s
4 - T
a
4 ),
T
s
> T
a .
where:
Ts = Absolute temperature of the blackbody
Ta = Absolute temperature of the surrounding medium (ambient temperature)
Related Topics
Basic Radiation Definitions
Radiation Emission from Real Surfaces
Radiation Exchange Between Surfaces
Examples of Radiation from Surfaces