Thermal Diffusivity

  • Thermal diffusivity (\(\alpha\)) where \(\alpha=k/(\rho C_P)\) is a convenient collection of physical properties for transient solutions of the heat equation.

  • Thermal diffusivity is a measure of the transient thermal response of a material to a change in temperature.

  • The larger the value of \(\alpha\), the faster will the heat diffuse through the material and its temperature will change with time. This will result either due to a high value of conductivity \(k\) or a low value of \(\rho, C_P\).

    Material Thermal Diffusivity
      (cm\(^2\)/s) at 300 K
    Copper 1.15
    Aluminum 0.97
    Stainless steel (304) 0.042
    Silicon dioxide (polycrystalline) 0.0083
    Water 0.0014
    Polyvinyl chloride (PVC) 0.0008
    Alcohol 0.0007
    Air 0.19

  • Metals and gases have relatively high value of thermal diffusivity and their response to temperature changes is quite rapid.

  • The non metallic solids and liquids respond slowly to temperature changes because of their relatively small value of thermal diffusivity.