Abstract
Experimental investigations have been reported on steady state forced convection heat transfer from the outer surface of horizontal triangular surface cylinders in cross flow of air. Two different horizontal positions are considered; one when the vertex of the triangle faces the flow and the other when the flat surface faces the flow. Four equilateral triangular cylinders have been used with cross section side length of 0.03, 0.05, 0.08 and 0.12 m, corresponding to blockage ratios 0.066, 0.110, 0.175 and 0.263 respectively. The cylinders are heated using internal constant heat flux heating elements. The temperatures along the surface and peripheral directions of the cylinder wall are measured. Local Nusselt numbers at the middle of the cylinder are obtained around the perimeter for the larger cylinders 0.12 and 0.08 m for various Reynolds numbers. Total overall averaged Nusselt numbers are obtained for transition to turbulent regime and these critical points are tabulated. Empirical correlations are obtained for the overall averaged Nusselt numbers and Reynolds number using the equilateral side length as a characteristic length for the two positions of the cylinders. Furthermore, other general correlations are obtained for the overall averaged Nusselt number using the cylinder length as a characteristic length and the blockage ratio as a parameter. (C) 2010 Elsevier Masson SAS. All rights reserved.