Thermal diffusivity

In heat transfer analysis, thermal diffusivity (symbol: , but note that the symbols α, D, and k are all commonly used) is the ratio of thermal conductivity to volumetric heat capacity.

Additional recommended knowledge

Safe Weighing Range Ensures Accurate Results

Essential Laboratory Skills Guide

How to ensure accurate weighing results every day?

where: is thermal conductivity (SI units: watts per metre-kelvin, W∙m^-1∙K^-1) is the volumetric heat capacity (density kg∙m^-3 times specific heat capacity J∙kg^-1K^-1; 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, ~ 10^-6 m²∙s^-1.

Thermal diffusivity of air at 300 K is 0.000024 m²/s.

For a plot of thermal diffusivity of air as a function of absolute temperature see James Ierardi's Fire Protection Engineering Site

See also

• Thermodiffusion
• Heat capacity
• Specific heat capacity
• Heat equation
• Thermal conductivity
• Thermal effusivity
• Thermal time constant