Influence of geometrical parameters and forced convective heat transfer in transversely corrugated circular tubes

A numerical investigation is performed to study the effects of different geometrical parameters on the thermal and flow fields through transversely corrugated circular tubes with Reynolds number ranging from 5000 to 60,000 and heat flux of 50 W/cm2. The optimization through nineteen transversely corrugated (roughened) tubes having 10 mm inner diameter was studied by changing the dimensions of roughness such as relative roughness height (e/d) in the range of 0.025–0.1, relative roughness pitch (p/d) in the range of 0.5–1.5 and relative roughness width (w/d) in the range of 0.05–0.2. For water as a working fluid, heat transfer can be increased with optimal roughness dimensions and maximum performance evaluation criterion (PEC). The results show that the corrugated tube performance was greatly influenced by the geometrical parameters. The Nusselt number increased as the roughness height, width and Reynolds number increased and with the decrease of roughness pitch. The highest Nusselt number was obtained with e/d = 0.1, while the efficient flow (max. PEC) was achieved with e/d = 0.025 for p/d = 0.5 and w/d = 0.2. For the rib-roughened tubes, the influence of Reynolds number on the friction factor is quite weak while it is increased with the increase of roughness height compared with the smooth tube.