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

11-1
of variables. A total of 616 data points were taken,
163 of which were used for screening the variables to
be studied and evaluating the effect of impeller height.
The remaining 453 data points were used to evaluate
the constants of the correlations presented in the previous
chapter..
Eleven different impellers representing the
fOl.ll'" major types in common practice 1..Jere used in collecting
the 4.53 points. The range of application is wide since
pseudoplastic as Hell as Newtonian fluids 1,rere used.
The
use of multiple-variable regression analysis Has a
valuable tool in reducing hcunan error and subjectiveness
in the calculation of the correlation constants.
The measurement of the wall temperature at three
different locations gave evidence of the considerable
difference in heat flux in diff'erent positions in the
vessel. Although the ef'fect was not quantitatively studied
it is the f'irst tLme it has been reported; and this opens
the door to a possibly fruitful field of' study.
It has
been shown that the variations in local heat transfer
rates can be minimized by proper location of' the impeller.
The vertical position of' the impeller Has shown to
have a large ef'fect on the Nusselt number in the range
studied, ie. f'or impeller height/liquid heie~t
ratios be-