Summary

The packed bed Reynolds number is dimensionless and describes the ratio of inertial to viscous forces for fluid flow through a packed bed. It may be used to calculate the pressure drop though a packed bed via the Ergun equation or identify the boundaries of flow regimes (laminar, transitional and turbulent) in a packed bed. This article will show you how to calculate and interpret the packed bed Reynolds number.

Definitions

Cross sectional area of the packed bed (m2)
Volumetric flow rate of fluid moving through the packed bed (m3/s)
Superficial fluid velocity (m/s)
Spherical equivalent particle diameter (m)
Bed voidage
Density of the fluid flowing through the packed bed (kg/m3)
Viscosity of the fluid flowing through the packed bed (Pa.s)


Calculation of Reynolds Number for flow through a packed bed

The regime for flow through a packed bed may be identified by the packed bed Reynolds number, which may be calculated as follows:

The superficial velocity is the velocity of the fluid moving through the packed bed as if it was the only phase. More simply put, the superficial velocity is the volumetric flow rate of the fluid divided by the cross sectional area of the packed bed:

Flow through Packed Bed

Packed Bed Reynolds Number and flow regime

The flow regime for flow through a packed bed may be identified from the packed bed Reynolds number. Typical packed bed Reynolds number boundaries are shown below:

Region Value
Laminar

Transitional

Turbulent