Thermal diffusivity

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In heat transfer analysis, thermal diffusivity (symbol: \alpha\,, but note that the symbols κ, D, and k are all commonly used) is the ratio of thermal conductivity to volumetric heat capacity.

\alpha = {k \over {\rho c_p}}

where:


The SI units for thermal diffusivity is m2/s.

Substances with high thermal diffusivity rapidly adjust their temperature to that of their surroundings, because they conduct heat quickly in comparison to their thermal 'bulk'.

For common rock material, \alpha\, ~ 10-6 m2/s.

Thermal diffusivity of air at 300 K is 0.000024 m2/s.

For a plot of thermal diffusivity of air as a function of absolute temperature see James Ierardi's Fire Protection Engineering Site

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