Packed Beds Flashcards
1
Q
Packed bed theory
A
Flow through identical channels (pipe flow analogy)
*more simple that discrete particle model which uses CFD
2
Q
2 criteria of pipe flow analogy
A
- equal area (of channels and original solids)
- equal volume of channels and liquid
3
Q
Where does lambda for turbulent and laminar flow come from?
A
empirical correlations
4
Q
Packed Bed: wall effects
A
if dp is roughly the same as column diameter, then the pressure drop will be smaller since the particles are not packed as closely near the column wall (larger particle diameter = less pressure drop)
5
Q
Packed Bed: non-spherical particles
A
- non–spherical particles have different delta P, in literature there are correlations with sphericity
- their drag coefficient is different
6
Q
Packed Bed: Structured Packing
A
- Ergun is not applicable - only for randomly packed beds
- structured (ex. absorption columns)
7
Q
Packed Bed: high voidage
A
correlations do not work well when voidage > 0.6 (less particles, so overestimates pressure drop)
8
Q
Packed Bed: Wetting Particles
A
- can drop delta P by 30% on non-wetting materials (particles are hydrophobic, so less surface contact for friction)
9
Q
Packed Bed: Non-Newtonian fluids
A
need different correlations
