1. Porous Flow

2. Porous Flow
Is a multiphase flow involving fluids passing through a permeable bed of particles
Process examples:
Catalytic converter
Drying column
Filtration (this will be cover in details later)
Objective: to predict pressure drop. Pressure drop prediction is complicated by the variety of solid materials and of their packing arrangement (or patterns)

4. Properties of Porous Particles
Porosity/Voidage/Void fraction ()
Is the fraction of volume that is not occupied by solid materials
Specific surface, S
Is the surface area of a particle divided by its volume
For a sphere:
For other shape particles:

6. Pressure Drop – Laminar Flow

7. Kozeny equation
Laminar Re<1 2

8. Example 2.1

11. Pressure Drop – Turbulent Flow

12. Use the same superficial velocity that was calculated
2.1
Example 2.2
Use the same superficial velocity that was calculated
Using laminar and turbulent equations

14. General Equation for Pressure Drop Calculation
Ergun equation

15. Example 2.3

17. 2

21. Pressure drop – Compressible Flow
Gas flow through a packed bed under conditions where there is appreciable pressure drop ( Compressible flow)
Because the pores between the particles are of different sizes, there may well be choked flow in small pores
Pressure drops are larger than expected because of coking
Computation of pressure drops should consider the overall energy equation:

22. Two Phase Flows in Porous Media
For gas liquid flow, liquid wets the surface of the particle (wetted fluid)
Gas flows through the larger pores that are limited with liquid, and thus does not make direct contact with the solid. Consequently, the gas experiences much less resistance to flow than the liquid (Non-wetting fluid)

23. Saturation
Is the fraction of the voidage occupied by the specific fluid
We can calculate the saturation for both the liquid and gas phase
Adding up to 1

26. Example 2.4
2.1

28. Counter-Current Flow

29. Gas-Liquid Flow