Prediction of batch heat transfer coefficients for pseudoplastic fluids ...

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than ror the non-Newtonians.
As the middle of the transition region is approached
(NR~
= 100) turbulence begins near or betvJeen the impeller
blades. For the pseudoplastics, this turbulence is rapidly
damped.
In the turbulent region there is much turbulence near
the impeller but it is damped out quickly at any distance
from the Lmpeller.
There is not as much turbulence ror the
Newtonian fluids but it extends further into the bulk of
the fluid.
In the horizontal plane of the impeller the local velocities
increase slightly more than linearly with rotational
speed for the NeHtonian r ..... 1uids. For the pseudoplastics the
increase in velocity is almost exponential.
Thus at high
shear x'ates the pseudoplastics may flow more than the NeHtoni8~l.s
1>Ihile at 10H rotational speeds the reverse is true.
Metzner et al. (122) used the onset of fluid movement
near the vessel Hall as a criterion for good mixing.
At low
Dt/Da ratios there is no advantage to using tHO turbines.
For values of Dt/Da above 2 .. 0 less power is consumed for
equal mixing if two tUl"bines are used, since at high values
of this ratio tHO turbines circulate hlice as much fluid
as one ..
The data indicate that propellers are only desirable