Ergun equation

The Ergun equation, derived by the Turkish chemical engineer Sabri Ergun in 1952, expresses the friction factor in a packed column as a function of the Reynolds number:

$f_p = \frac {150}{Gr_p} + 1.75$

where $f_p$ and $Gr_p$ are defined as

$f_p = \frac{\Delta p}{L} \frac{D_p}{\rho V_s^2} (\frac{\epsilon^3}{1-\epsilon})$ and $Gr_p = \frac{D_p V_s \rho}{(1-\epsilon)\mu}$

where: $\Delta p$ is the pressure drop across the bed,
$L$ is the length of the bed (not the column),
$D_p$ is the equivalent spherical diameter of the packing,
$\rho$ is the density of fluid,
$\mu$ is the dynamic viscosity of the fluid,
$V_s$ is the superficial velocity (i.e. the velocity that the fluid would have through the empty tube at the same volumetric flow rate), and
$\epsilon$ is the void fraction of the bed(Bed porosity at any time).

Extension of the Ergun equation to fluidized beds is discussed by Akgiray and Saatçı (2001).

See Also

Kozeny–Carman equation

References

• S. Ergun, Chem. Process Eng. London 48, 89 1952.
• Ö. Akgiray and A. M. Saatçı, Water Science and Technology: Water Supply, Vol:1, Issue:2, pp.65-72, 2001.