Chapter: Mechanical : Heat and Mass Transfer : Radiation

Stefan-Boltzman Law

Both Stefan and Boltzman were physicists; any student taking a course in quantum physics will become well acquainted with Boltzman’s work as he to the field.

Stefan-Boltzman Law

Both Stefan and Boltzman were physicists; any student taking a course in quantum physics will

become well acquainted with Boltzman’s work as he to the field. Both were contemporaries of Einstein so we see that the subject is of fairly recent

vintage. (Recall that the basic equation for convection heat transfer is attributed to Newton)

where: Eb = Emissive Power, the gross energy emitted from an ideal surface per unit area, time.

⋅ -8 2⋅4

σ = Stefan Boltzman10W/mK constant, 5.67

Tabs = Absolute temperature of the emitting surface, K.

Take particular note of the fact that absolute temperatures are used in Radiation. It is suggested, as a matter of good practice, to convert all temperatures to the absolute scale as an initial step in all radiation problems.

You will notice that the equation does not in the emissive power. The relationship between these terms is as follows. Consider two infinite

plane surfaces, both facing one another. Both surfaces are ideal surfaces. One surface is found to be at temperature, T1, the other at temperature, T2. Since both temperatures are at temperatures above absolute zero, both will radiate energy as described by the Stefan-Boltzman law. The heat flux will be the net radiant flow as given by:

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Mechanical : Heat and Mass Transfer : Radiation : Stefan-Boltzman Law |