# Thermal Diffusivity

In heat transfer analysis, the thermal conductivity ratio to the specific heat capacity at constant pressure is an important property termed thermal diffusivity. The thermal diffusivity appears in the transient heat conduction analysis and the heat equation.

It represents how fast heat diffuses through the material and has units m2/s. In other words, it is the measure of the thermal inertia of given material. Thermal diffusivity is usually denoted α and is given by: As can be seen, it measures the ability of a material to conduct thermal energy (represented by factor k) relative to its ability to store thermal energy (represented by factor ρ.cp). Materials of large α will respond quickly to changes in their thermal environment. In contrast, materials of small α will respond more slowly (heat is mostly absorbed), taking longer to reach a new equilibrium condition. ## Thermal Diffusivity in Heat Conduction Equation

Constant Thermal Conductivity

This equation can be further reduced assuming the thermal conductivity to be constant and introducing the thermal diffusivity, α = k/ρcp: References:
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