Fourier number

The Fourier number (Fo, after Jean Baptiste Joseph Fourier ) is a dimensionless parameter for problems of transient heat conduction. It indicates the ratio of guided to stored sensible heat and is defined as

The thermal diffusivity, the sizes ( thermal conductivity ), ( specific heat capacity at constant pressure) and (density) summarizes, while standing for the time and for a characteristic length of the problem.

Applications

  • Different size, but geometrically similar problem of unsteady heat conduction show an identical development of the temperature field when the Fourier number is used as a time coordinate.
  • At a periodic, one-dimensional thermal wave the Fourier number has the value π if used for the inverse of the excitation frequency and the depth of penetration in the homogeneous material.
  • With the exponential cooling of a body with insulating the Fourier number, paired with the Biot number, the size of temperature differences within the body to the temperature difference to the outside.
  • If the unsteady heat conduction through a stationary pipe flow into existence ( non-stationary in the co-moving with the flow reference system ), the inverse of the Fourier number, Graetz number is called, the ratio of convective heat transfer to heat conduction in the stationary reference system.
  • Code ( thermodynamics)
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