Module 9: Packed beds
  Lecture 30: Pressure-drop: Ergun's equation
 
 
For a packed–bed

(Propose)

(Re-call: wall shear-stress in tubular laminar flow,

 

Similarly, pressure–drop at high Reynolds number, . Therefore, Pressure-drop in packed beds is related to pressure–drop due to viscous and inertial effects via two empirical constants, .

 
  (multiply both numerator and denominator by L)
  , SO = cross sectional area of packed–bed