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

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of the fluid flO'i>Jing tln">ough the co iI, or a.."l average of
these t\:.;ro values..
It must be remembered, however, to
correct for heat exchange between the jacket fluid ~nd
the
surroundilJ.gs ..
For the unsteady-state experiment the heat transferred
Can be calculated from the product of the flow rate of the
heat transfer medium and its enthalpy change..
This value
must be corrected for heat losses to the surroundings and
the gain in heat content of the vessel..
If steam is the
heating medium in the jacket the condensate flow-rate must
be measured as Hell as its temperature.
It is this authorfs
experience that this f1O't-J rate is not constant during a
heating run ~nd
thus the condensate collected during one
time interval, had actually condensed during an unknO't-JU
previous time interval. Hence~its
measurement is subject
to large errors. If the heating or cooling medium is \-Jater
the 1'101-1 rate is usually very high in an effort to keep the
heat transfer surface at a constant temperature over its
entire surface at anyone time..
Therefore the actual
change in temperature of the floVoring fluid is kept small ..
This also leads to large errors because a fraction of a
degree error in the inlet and outlet temperature readings
is often a large fractional error of the actual temperature
change..
In addition to these errors there are the problems
of calculating the heat losses to the surroundings and the