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

70
(3-71
The ratio Dt/HL is a constant for all the heat transfer data
t~{en fu~d thus has no meaning for the enclosed data. The
ELIDa term could be used as such, however the fluid height
",ras not varied and thus HL is a constant..
Other authors
(137, 150, 160) have correlated data using Dt/Da and the
use of this group is useful for s~{e of comparison. Since
Dt is a constant it may be substituted for HLo
Equation
3-71 may thus be lrJritten.
I~ (3-72
The original set of equations vJaS set up assuming a
constant fluid consistency index, K..
HOvJever, in practice
the consistency at the wall is usually quite different from
the consistency of the batch because of the large temperature
gradient. A fourth dimensionless group, K/K w , is thus intraduced
to correct empirically for the consistency index
dependence upon temperature.
The use of K/K"'J has been
successfully used Ln similar problems in both Newtonian and
non-Newtonian systems.
Although the exact form of the function in equation
3-72 is not known, it is assumed that equation 3-73 l