Wall Heat Transfer in Stirred Tank Reactors

Local wall heat-transfer coefficients have been measured for water and for the non-Newtonian systems consisting of 0.3, 0.6, and 1.0 wt % carboxymethylcellulose in water. The results were compared to existing correlations, and good agreement was found for the water system outside the impeller region. In the impeller region, deviations were large. For the nonNewtonian systems, a functional dependence between the Reynolds number and the heat-transfer coefficient, given by Nu/(Pr0.33Vi0.14) (alpha)Re0.8, was found to fit the data well. Support for this was found by a closer examination of the existing literature. This is in contrast to the currently accepted dependence on a Reynolds number exponent of 0.67-0.68. On the basis of the data, a new correlation for non-Newtonian fluids has been suggested. Radial temperature profiles for the wall region were also measured and presented.