Thermal diffusivity
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(Redirected from Diffusivity)
In heat transfer analysis, thermal diffusivity (symbol: <math>\alpha</math>) is the ratio of thermal conductivity to volumetric heat capacity.
- <math>\alpha = {k \over {\rho c_p}}</math>
where:
- k is thermal conductivity (SI units: watts per metre-kelvin, W∙m-1∙K-1)
- ρcp is the volumetric heat capacity (density times specific heat capacity; SI units: joules per cubic metre-kelvin, J∙m-3∙K-1)
The SI units for thermal diffusivity are square metres per second or m2∙s-1.
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, <math>\alpha \approx</math> 10-2 cm2∙s-1.
