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

42
disadvantage is the installation of the thermocouples so
that the junction measures the heat transfer surface and
does not disturb the heat flow through the wall.
By proper
installation techniques, hov-rever, this can be closely
approximated.
In some cases the thermocouple junction has
been embedded in the 't\fall rather than at the surface..
However,
if the exact position of the junction and the thermal
conductivity of the wall is knovrn the results can be
corrected to give the surface temperature.
The Correlation of Results
- ,
The correlation of the data is difficult because of
the large number of variables.. A fe'ltJ authors used a
method of plotting the Nusselt n~mber versus a dimensionless
group on logarithmic coordinates, keeping all the variables
constant (39, 58, 137,1;D)"
Once the effect of
Ylgroup 1" has been determined the Nusselt number, divided
by the IIgroup ll! effect, is plotted versus "group 2".
The effect of "group 3 11
is found by plotting the Nusselt
number, divided by 'che product of the "group 111
and flgroup
211 effect, versus ltgroup 3". There are disadvantages to
this method since it is very difficult, experimentally, to
change the value of only one dimensionless group at a time.
Some authors seem to have assltmed that the Chilton (39
equation and exponents are accurate and thus use his exponents
for some of the dimensionless groups and by plotting