Enhanced forced convection in triangular ducts by roughened surface

Experimental investigations had been conducted to study the forced convection of fully-developed turbulent flow in horizontal equilateral triangular ducts fabricated with the same length and hydraulic diameter, but different surface roughness of 1.2 mu m, 3.0 mu m and 11.5 mu m. The experiments were performed with the hydraulic diameter based Reynolds number ranged from 7000 to 20000. The entire inner wall of the duct was heated uniformly and the outer surface was thermally insulated. It was concluded that the duct with a higher surface roughness can enhance the convective heat transfer performance. Non-dimensional expressions for the determination of the heat transfer coefficient of the equilateral triangular ducts with different surface roughness were also developed.