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

94-
was about 40-45 ndmutes ..
Tke impeller speed r~ge was limited both at the IGwer
~d upperspee~s.. The motor itself eould not operate well
below 75 RPM and thus this limited the range.. Often the
lewest speed l!t:sed was considerably ab0Te 75 RPM, however,
beeause lower speeds did not mix the fluid thoroughly and
the hot fluid would stratify at the tep of the bateh.. If
there "ras evidence 0f ineemplete mixing (baton temperatu::t"e
po~ts not on same sm00th e~e) the data taken were dis-
The great~st speed used was also l~ited.. The viscosity
data for tae non-Newtomians was limited te sheap
rates belbw 4zr:~1AX/n where NMAX is 600 RPM, the highest
speed of the v~se0meter. Aceording to Metzmerts results the
shear ~ afl agitated vessel is 11 .. 5 N where N is the RPM at
the impeller.. Smce 4 7r is fairly close to 11 .. 5 the maxi:m.u.nt
rotational speed which eould be used, without exeeediEg the
above shear rate" is lirrl ted to 600-700 RPr-1 ..
The motor and power supply lLmited the top speed
attainable for the very viscous fluids because the power
output of the system vIas exceeded bef'ore the larger impellers
reached 600 RPM ..
Because of these limitations the a.m.otm.t of data.