Advanced Radiation Heat-Transfer Principles

Radiation spectrum and thermal radiation. Energy can be transported in the form of 

When different surfaces are heated to the same temperature, they do not all emit or absorb the same amount of thermal radiant energy. A body that absorbs and emits the maximum amount of energy at a given temperature is called a black body. A black body is a standard to which other bodies can be compared. 

Planck s law and emissive power. When a black body is heated to a temperature T, photons are emitted from the surface which have a definite distribution of energy. 

For a given temperature, the wavelength at which the black-body emissive power is a maximum can be determined by differentiating Eq. (4.11-1) with respect to A at constant T and setting the result equal to zero. The result is as follows and is known as 

4 Principles of Steady-State Heat Transfer 

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