I. Azevedo et al., LAMINAR COOLING OF PSEUDOPLASTIC FLUIDS FLOWING THROUGH CYLINDRICAL HORIZONTAL PIPES, International journal of heat and fluid flow, 16(2), 1995, pp. 125-130
We present results concerning heat transfer for pseudoplastic fluids f
lowing inside cylindrical tubes. The fluids are cooled by an external
turbulent counterflow of water. A method is developed to evaluate the
values of the local heat exchange coefficients. The variations of the
associated Nusselt numbers can be approached using the dimensionless a
xial abscissa X(+) = (2z/D)/Pe. Experimentation shows that the Nusselt
numbers remain slightly dependent on the difference between the inlet
temperature of the pseudoplastic fluid T-e and the wall temperatures
T-W(z). This last phenomenum, attributed to the variations of consiste
ncy K and rheological index n with temperature, can be linked to the e
volutions of the axial velocity profiles, experimentally determined by
laser Doppler anemometry. A very simple correlation Nu(z) = 1.15{(3n
+ 1)/(4n)}(1/3){1 - 0.008[T-e - T-W(z)]} X(+)(-0.36) Seem to be accept
able in our experimental range. Comparisons with numerical predictions
are also proposed.