# Thermal Diffusivity

Written by Jerry Ratzlaff on . Posted in Thermodynamics

Thermal diffusivity, abbreviated as $$\alpha$$ (Greek symbol alpha), is a measure of the transient thermal reaction of a material to a change in temperature.

## Thermal diffusivity formula

 $$\large{ \alpha = \frac{ k }{ \rho \; Q } }$$

### Where:

 Units English Metric $$\large{ \alpha }$$  (Greek symbol alpha) = thermal diffusivity $$\large{\frac{ft^2}{sec}}$$ $$\large{\frac{m^2}{s}}$$ $$\large{ \rho }$$  (Greek symbol rho) = density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$\large{ Q }$$ = specific heat capacity $$\large{\frac{Btu}{lbm-F}}$$ $$\large{\frac{kJ}{kg-K}}$$ $$\large{ k }$$ = thermal conductivity $$\large{\frac{Btu}{hr-ft^2-F}}$$ $$\large{\frac{W}{m-K}}$$

## Related Thermal Diffusivity formulas

 $$\large{ \alpha = \frac{ Fo \; l_c^2 }{ t } }$$ (Fourier number) $$\large{ \alpha = Le \; D_m }$$ (Lewis number) $$\large{ \alpha = \frac{ \nu }{ Pr } }$$ (Prandtl number)

### Where:

$$\large{ \alpha }$$  (Greek symbol alpha) = thermal diffusivity

$$\large{ l_c }$$ = characteristic length

$$\large{ Fo }$$ = Fourier number

$$\large{ \nu }$$  (Greek symbol nu) = kinematic viscosity

$$\large{ Le }$$ = Lewis number

$$\large{ D_m }$$ = mass diffusivity

$$\large{ Pr }$$ = Prandtl number

$$\large{ t }$$ = time 