Forced convection heat transfer from a sphere to non-Newtonian power law fluids



The effects of Reynolds number (Re), Prandtl number (Pr), and power law index (n) on the heat-transfer characteristics of an unconfined sphere submerged in an isothermal and incompressible power law fluid, for different thermal boundary conditions (isothermal and isoflux) on the sphere surface, have been investigated numerically for the 2-D axisymmetric and steady flow by using a finite volume method over the ranges of conditions as 5 ≤ Re ≤ 200, 1 ≤ Pr ≤ 400 (the maximum value of the Peclet number is 2000), and 0.5 ≤ n ≤ 2. Based on the numerical results obtained herein, simple heat-transfer correlations are developed for the constant-temperature and the constant heat-flux boundary conditions to estimate the value of the Nusselt (Nu) number in a new application. Furthermore, the variation of the local Nu over the surface of the sphere has been studied to delineate the effects of Re, Pr, and n on heat transfer from a sphere, thereby showing the extent of heat transfer from the front and the rear parts of the sphere. © 2006 American Institute of Chemical Engineers AIChE J, 2006