Variable Physical Properties in Laminar Heating of Pseudoplastic Fluids with Constant Wall Heat Flux

Abstract

A theoretical investigation of the combined influence of natural convection and consistency variations in laminar heating of non-Newtonian fluids has been carried out. The heating of a power law fluid with an initially fully developed velocity profile flowing upward through a vertical tube with a constant wall heat flux was considered. The system of governing equations, complete with the convective terms, was solved numerically. Detailed comparisons with previous theoretical and experimental results were performed to check the integrity of the solutions obtained with the present approach. Local heat transfer coefficients, as a function of Graetz number, were presented. Local heat transfer results showed that for pseudoplastic fluids with smaller Prandtl number the parameter Pr was very important in the inlet and in the intermediate part of the tube.