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

605·36
Llbrary
Newark Colle e of Enp:lneerfn
ABSTRA.CT
Experimental batch heat-trans~er
data were obtained
for both Newtonian ~nd
pseudoplastic liquids in a baffled
agi tated vessel.
The fluids tested had flo1f behavior indexes
between 0.36 and 1.0; and the apparent viscosity
ranged from 1 to 1200 centipoise. Four types of impellers
(anchor, paddle, propeller, and disk and vane turbine)
were studied using eleven separate impellers.
The probable
error in the measured heat trall.sfer coefficient was ± 20
percent.
The effects of the generalized Reynolds number, generalized
Prandtl number, and viscosity ratio were studied.
In
addition the effect of impeller diameter was studied for
paddles, propellers, and turbines; and the effect of impeller
width was studied ~or the paddles and turbines. The
vertical height of the impeller above the bottom of the
vessel was shown to be a significant variable.
The data for the Newtonian liquids, in general, substantiated
presently accepted correlations. For the pOi..Jer
laH pseudoplas tic fluids bJO correlations 1.Jere developed ..
One correlation l'1faS based on the dimensional analysis of
the equations describing a flOi..] model of the system.
The
second correlation is based on Metzner's evaluation of the
rate of shear in an agitated vessel.
The former correlation
has five to seven constants which vary with impeller type