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

166
rive different temperatures; about 17~
25, 40, 60 and 82 °e.
The fluid Has maintained at the desired temperature by
iramersing the 600 ml ..
beaker in a constant temperature
bath..
The constant temperature bath was placed on a magnetic
stirrer (the stirring bar Has in the 600 ml.. beru-rer)
which was run l'lhile bringing the fluid up to temperature,
but Has shut off while rheological data 14ere being taJcen.
The temperature could be held constant 1AJ"ithin 0.1 degree
Centigrade,
A grooved cast acrylic lid was also fabricated
to cover the 600 mI. beaker Hhile the Carbopol solutions
were at the higher temperatures to prevent evaporation
losses..
The apparatus is sh01m in Figure A-3.
The average of the three readings of torque 1...ras used
to calCUlate the shear stress. nn, the slope of the logaritlLmic
plot of torque (or shear stress) versus rotational
speed, ""'las needed to calculate the shear rate. n ll v-Jas evaluated
for each fluid at each temperature using a linear regression.
The actual calcu~ations Here performed by the IB}1
1620 digital computer. The computer programs are enclosed
at the End of this Appendix.
The slope for each condition
is listed in Table A-4.
The shear rate at each point was then calculated using
equation 2-12.
The apparent viscosi t·y Has calculated using
(2-23