Fourier Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Fourier number is a dimensionless number giving the ratio of heat conduction rate to the rate of thermal energy storage in a solid.  This is mainly used in unsteady state heat transfer.


\(Fo = \frac{\alpha t}{l^2}\)


\(Fo\) = Fourier number

\(\alpha\) = thermal diffusivity

\(t\) = time

\(l\) = characteristic length

Solve for:

\(\alpha = \frac{  Fo l^2    }{ t }\)

\( t = \frac{  Fo l^2    }{ \alpha }\)

\(L =  \sqrt   { \frac{ \alpha t }{ Fo }  }\)