Effect of surface roughness on cost effectiveness of equilateral triangular passage heat exchanger

Experimental investigations had been conducted to study the forced convection heat transfer and pressure drop characteristics of fully-developed turbulent flow in horizontal equilateral triangular ducts fabricated with duralumin (thermal conductivity, kf= 180 W/(m.K)). There were three ducts constructed with the same duct length (L) of 2.4 m and hydraulic diameter (D) of 44 mm, but different average surface roughness (Ra) of 1.2 μm, 3.0 μn and 11.5 μm respectively. The triangular duct was used to simulate the triangular passage of a plate-fin compact heat exchanger. The entire inner wall of the duct was heated uniformly, while the outer surface was thermally insulated. The experiments were performed with the hydraulic diameter based Reynolds number (Rev) ranged from 7000 to 20000. It was found that the duct with a higher surface roughness has a better heat transfer performance, but also encounter a higher friction lass. Nan-dimensional expressions for the determination of average heat transfer coefficient (h) and friction factor if) of the equilateral triangular ducts with different average surface roughness were developed from the generalization of the experimental results. based on these developed equations, effect of surface roughness on the cost effectiveness of the equilateral triangular passage compact heat exchanger was then investigated.