HEAT-TRANSFER TO POWER-LAW FLUIDS FLOWING IN PIPES AND FLAT DUCTS WITH VISCOUS HEAT-GENERATION

This paper aims to show the application of the analytical approach presented recently by Gottifredi et al. [Int. J. Heat Mass Transfer 26, 1215-1220 (1983)] to the generalized Graetz-Nusselt problem, in order to estimate the mixing-cup temperature of a power-law fluid which is flowing through a duct whose walls are maintained at constant temperature. Steady and laminar flow conditions as well as constant thermophysical properties of the fluid are assumed. The effect of heat generation by viscous dissipation is also considered. The technique is very simple and a unique expression of the mixing-cup temperature valid for both cylindrical and plane geometries is generated. This expression provides results which are in good agreement with those reported by previous authors in the whole range of Graetz numbers (0 less-than-or-equal-to Gz less-than-or-equal-to infinity).