Laminar natural convection from a horizontal cylinder in power-law fluids

Abstract

In this work, free convective heat transfer from a horizontal cylinder immersed in quiescent power-law fluids has been investigated numerically in the laminar flow regime. The governing differential equations (continuity, momentum, and energy) have been solved over the following ranges of conditions: Grashof number, 10 ≤ Gr ≤ 10⁵; power-law index, 0.3 ≤ n ≤ 1.8; Prandtl number, 0.72 ≤ Pr ≤ 100. The flow and heat transfer characteristics have been visualized in terms of streamlines and isotherm contours which help delineate the regions of high/low temperature. As expected, the value of the local Nusselt number decreases from its maximum value at the front stagnation point along the surface of cylinder, as the flow remains attached to the surface of the cylinder over the range of conditions covered in this study. Finally, the surface-averaged Nusselt number shows positive dependence on both Grashof and Prandtl numbers. All else being equal, shear-thinning behavior enhances the rate of heat transfer with reference to its value in Newtonian fluids. Shear-thickening behavior, however, has an adverse influence on heat transfer. The paper is concluded by presenting comparisons with the previous approximate analysis and scant experimental data available in the literature.