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

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The effect of using a 10"1 (0,,1.4-) exponent for the
viscosi ty ratio also increases the error 1"hen comparing the
eight inch by one inch paddle data (geometrically similar
to Chilton) with Chilton's (39) correlation. Comparing the
date to Chilton's equation there is an average error ofl:
16.3 percent. Uhl recalculated Chiltonts data and claLms
that the exponent of the viscosity ratio should be 0 .. 2.4-
instead of 0.14.
Using l;'hl! s modification of Chilton I s
equation there is an average deviation of± 11.1 percent
between the predicted and measured Nusselt numbers.
The
results are plotted in Figure 6-2.
The points are fairly
evenly distributed along the line of perfect agreement.
It ,,,ould be expected that the meaS1.U'ed values vJOuld be
about 10 to 20 percent above the predicted values since Chilton
did not use baffles. However, Chilton measL~ed
the
wall temperature at only one position, just opposite the
impeller. This '--Tould lead to a measured driving force l--Thich
lIms less than the actual value, causing the calculated
Husselt nu.mbers to be greater than they should be.
Naturally
the correlation based on this data would predict Nusselt
numbers which are too high.
The propeller data were compared w~th Brown's (32)
correlation and are plotted in FigLU'e 6-3. The average
deviation is 26 .. 9 percent and thus the fit is not very good.
ROV-lever, Brown t s correlation is only based on limited data,