Chapter 2
2.3.3. Sedimentation and creaming
Sedimentation or creaming takes place when the two liquids exhibit different
densities due to gravity. Stokes equation can describe the terminal sedimentation
velocity of spheres in Newtonian fluids.
v∙= [2-91
18τ∕c
Here vs is the terminal sedimentation velocity, ∆p is the density difference of
dispersed and continuous phase, d is the diameter of droplet, ηc is the viscosity of
continuous phase, g is the acceleration either due to gravity (g = 9.81 m∕s2) or to
centrifugation (g = Lω2, with L being the effective radius of the centrifuge and ω
the angular velocity). If ∆p > O, emulsions sediment; otherwise, the process is
referred to as creaming. Sedimentation applies to most W/0 emulsions and solid
dispersions; creaming applies to most 0/W emulsions and bubbles dispersed in
liquids.
Eq. [2.9] is only satisfied for very dilute dispersions. If the volume fraction of
the dispersed phase φ is significant (say φ > 0.01), so-called hindered
sedimentation takes place. In general, the effect of φ is to reduce the
sedimentation rate due to hydrodynamic interactions among droplets. The
expression is as follows [16]:
16
More intriguing information
1. Gender and headship in the twenty-first century2. Ronald Patterson, Violinist; Brooks Smith, Pianist
3. The Advantage of Cooperatives under Asymmetric Cost Information
4. Commitment devices, opportunity windows, and institution building in Central Asia
5. Cyclical Changes in Short-Run Earnings Mobility in Canada, 1982-1996
6. Education Research Gender, Education and Development - A Partially Annotated and Selective Bibliography
7. THE EFFECT OF MARKETING COOPERATIVES ON COST-REDUCING PROCESS INNOVATION ACTIVITY
8. An Estimated DSGE Model of the Indian Economy.
9. Death as a Fateful Moment? The Reflexive Individual and Scottish Funeral Practices
10. A methodological approach in order to support decision-makers when defining Mobility and Transportation Politics