3. Basic definitions
Agitation :
Induced motion of a
material in a specified
way ,usually in a
circulatory pattern inside
some sort of a container.
Mixing :
Random distribution into
and through one another
,of two or more initially
separate phases.
4. A simple example
Gas A Gas B
blending
Sample A Sample B
Same composition = Agitation
7. Blending of two miscible liquids ( ethyl alcohol and water).
Dissolving solids in liquid ( salt in water).
liquid-liquid dispersion (dispersion of pigment in solvents ).
Suspending of fine solid particles in a liquid ( catalytic
hydrogenation of a liquid).
Agitation of the fluid to increase heat transfer between the
fluid and a coil or jacket in the vessel wall.
dispersing a gas in a liquid as fine bubbles, such as oxygen from
air in a suspension of microorganisms for fermentation or for
the activated sludge process in waste treatment.
Where is it used….??
8. The basic design
Influencing factors for
achieving a needed amount
of mixture or quality of
mixing :
1) Dimensions of the liquid
content of the vessel.
2) Dimensions and
arrangement of the
impellers , baffles .
http://commons.wikimedia.org/wiki/File:A
gitated_vessel.svg
9. The vessel shape .
The type , size , position and speed of the impeller.
Flow patterns.
Vortex formation.
Baffles.
Power correlations.
Design factors
10. The vessel
Rounded to eliminate
sharp corners or
regions into which
fluid currents would
not penetrate .
Height of fluid =
diameter of the
vessel
http://commons.wikimedia.org/wiki/File
:Agitated_vessel.svg
13. Based on
viscosity
Based on
flow pattern
impellers
Axial – flow
impellers
propellers
High
efficiency
impellers
Radial – flow
impellers
turbines
Types …..!!!
18. Impeller location : 1/6 the liquid level from the bottom
Impeller speed : standard speeds are 37, 45, 56, 68, 84, 100, 125, 155, 190, and
320rpm.
Power requirements usually are not great enough to justify the use
of continuously adjustable steam turbine drives.
Impeller size : the ratio of diameters of impeller and vessel falls in the range,
d/D,=0.3-0.6.
Another rule is that a second impeller is needed when the liquid must travel more
than 4 ft before deflection.
19. Depend upon :
The type of the impeller
The characteristics of the liquid(especially viscosity)
The size and proportions of : 1) tanks
2) baffles
3) impeller
Flow patterns
29. A simple numerical
For a vessel containing 5000 gal of liquid with specific gravity = 0.9
and viscosity of lOOcP, find size and speed of a pitched turbine
impeller to deliver 2 hp/1000 gal. Check also the superficial linear
velocity
Solution :
1) Size : d = 0.40 = 0.4(9.5)(12) = 45.6 in , say 46 in .
2) P= 2V = 2(5) = lO hp. (1 hp = 0.74 kW) = 7.4 kW .
36. The performance of a particular agitator usually
cannot be predicted quantitatively.
Agitator design is largely in exercise of judgment so
a considerable variety has been put forth by various
manufacturers.
Developing software .
Conclusion
37. www.fusionfluid.com
www.checalc.com
www.wikipedia.org
www.bakker.org
www.pacontrol.org
www.safaribooks.org
Unit Operations of Chemical Engineering (7th
edition)(McGraw Hill Chemical Engineering
Series)Warren McCabe Julian Smith Peter Harriott
www.dynamixinc.com
Bibliography
Editor's Notes
But we do not have a cooling jacket … cause regulating a temperature may not be that important .. Check with upstream.