The effects of tube Dimples-Protrusions on the thermo-fluidic properties of turbulent forced-convection

Abstract

Among the techniques offered to improve the efficiency of heat exchangers, the Dimpled surfaces were repeatedly reported as an applicable solution. In this regard, the current study is formed to evaluate the thermofluidic performance of Dimpled-Protruded tubes while following four novel investigations. Firstly, the impact of Protrusions next to the typical Dimple shape on the turbulence mixing and the forced-convection phenomenon was investigated. Secondly, a detailed comparison was carried out between the interfacial heat transfer of the Dimpled-Protruded tube and the smooth equivalent. Thirdly, a novel Dimpled-Protruded arrangement was utilized, and its thermal performance was evaluated in various Reynolds ( Re ) numbers. Lastly, both zonal and interfacial heat transfer mechanisms intensified by using Dimpled-Protruded shapes were scrutinized. Based on the results, the small vorticities at the Dimpled-Protruded locations were responsible for increasing the interfacial heat transfer. Moreover, the rough tube prompted the flow turbulence at lower Re ; thus, the heat transfer improved by 36.21% compared with the smooth type. Meanwhile, although the convective heat transfer improved up to 84.46%, the friction losses increased between 25% and 60% as the Re increased. Fortunately, however, the friction effects have produced insignificant pressure drops, proving that Dimpled-Protruded tubes effectively improve forced-convecting heat transfer.