Thermal Diffusivity

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Equation / Last modified by KurtHeckman on 2018/05/15 13:10
MichaelBartmess.Thermal Diffusivity

The Thermal Diffusivity calculator computes the thermal diffusivity (α) of a material based on the thermal conductivity (κ), density (ρ) and the material's specific heat capacity.(cp).

INSTRUCTIONS: Choose units and enter the following:

  • (k) This is the thermal conductivity expressed as power (e.g. Watts) per (m•K)
  • (ρ) This is the density of the material
  • (cp) This is the material's specific heat capacity expressed as energy (e.g. Joule) per (kg•K)

The Math / Science

The Thermal diffusivity of a material at a constant pressure is equal to the material's thermal conductivity divided by its density and its specific heat capacity. Thermal diffusivity is often used in Geosciences / Atmospheric Science.  The formula for thermal diffusivity is:

    α =  k / (ρ•cp)


  • α is the thermal diffusivity (m2/s)
  • k thermal conductivity (W /(m•K))
  • ρ is the density (kg/m³)
  • cp is the specific heat capacity (J/(kg•K))

Note: this calculator permits the user to adjust the units of power in the thermal conductivity factor.  However, the power is converted to Watts and then placed in a ratio of Watts per meter-degrees Kelvin (W /(m•K)).  In a similar vein, this calculator permits the user to adjust the units of energy in the specific heat capacity factor.  However, the energy is converted to Joules and then placed in a ratio of Joules per kilogram-degrees Kelvin (J/(kg•K)).