# Blackbodies, Emissivity and Real Surfaces

where: ε = emissivity of the radiating surface

Real Surfaces:

## Stefan-Boltzmann Law

:The maximum radiation rate at which energy can be emitted

from a surface is given by:

from a surface is given by:

where:

A

= Surface area perpendicular to heat transfer (m2)

σ

Ts

= Stefan-Boltzmann Constant = 5.67 x 10-8 W/(m2-K4)

= Absolute temperature of the surface (K)

The emissivity of a surface, ε, quantifies its ability to radiate.

A blackbody has an emissivity of one (ε = 1) and real substances have an emissivity between zero and one (0 <ε< 1).

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