Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.
Experimental investigations have been reported on steady state forced convection from the outer surface of horizontal triangular surface ducts in cross flow of air. The triangular cylinder was set such that its vertex faces the flow. Four equilateral triangular ducts 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 ducts are heated using internal constant heat flux heating elements. The temperatures along the surface and peripheral directions
of the duct wall are measured. Local Nusselt numbers at the middle of the duct are obtained around the perimeter for the larger ducts 0.12 and 0.08 m for various Reynolds numbers. Total overall averaged Nusselt numbers are obtained for transition to turbulent regime and critical points are tabulated for turbulent distinction. Empirical correlations are obtained for the overall averaged Nusselt numbers and Reynolds number using the equilateral side length as a characteristic length. Furthermore, other general correlations are obtained for the overall averaged Nusselt number using the duct length as a characteristic length and the blockage ratio as a parameter.