Thermal diffusivity
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In heat transfer analysis, thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure. It measures the rate of transfer of heat of a material from the hot end to the cold end. It has the SI derived unit of m2/s. Thermal diffusivity is usually denoted by α but a, h, κ (kappa), and D are also used.
The formula is:
- α = k /(ρ·cp)
where
- k is thermal conductivity (W/(m·K))
- cp is specific heat capacity (J/(kg·K))
- ρ' is density (kg/m3)
Together, ρ·cp can be considered the volumetric heat capacity (J/(m3·K)).
Thermal diffusivity is often measured with the flash method. It involves heating a strip or cylindrical sample with a short energy pulse at one end and analyzing the temperature change (reduction in amplitude and phase shift of the pulse) a short distance away.
