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In heat transfer analysis, thermal diffusivity (symbol: 
, but note that the symbols κ, D, and k are all commonly used) is the ratio of thermal conductivity to volumetric heat capacity.
where:
: thermal conductivity (SI units : W/(m K) )
: volumetric heat capacity (SI units : J/(m3K) )
: density (SI units : kg/(m3) )
: specific heat capacity (SI units : J/(kg K) )
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, ~ 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
See also
- Thermodiffusion
- Heat capacity
- Specific heat capacity
- Heat equation
- Thermal conductivity
- Thermal effusivity
- Thermal time constant
Wikipedia content modification information:
- This page was last modified on 5 August 2008, at 08:28.
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