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

Abstract

<p>Among the techniques offered to improve the efficiency of <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/engineering/heat-exchanger" target="_blank">heat exchangers</a>, 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 <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/engineering/heat-transfer" target="_blank">heat transfer</a> 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 (<em>Re</em>) numbers. Lastly, both zonal and interfacial heat transfer mechanisms intensified by using Dimpled-Protruded shapes were scrutinized.</p> <p>Based on the results, the small vorticities at the Dimpled-Protruded locations were responsible for increasing the interfacial heat transfer. Moreover, the <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/engineering/rough-tube" target="_blank">rough tube</a> prompted the <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/engineering/flow-turbulence" target="_blank">flow turbulence</a> at lower <em>Re</em>; thus, the heat transfer improved by 36.21% compared with the smooth type. Meanwhile, although the <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/engineering/heat-convection" target="_blank">convective heat transfer</a> improved up to 84.46%, the <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/engineering/friction-loss" target="_blank">friction losses</a> increased between 25% and 60% as the <em>Re</em> increased. Fortunately, however, the <a href="https://www-sciencedirect-com.myaccess.library.utoronto.ca/topics/engineering/friction-effect" target="_blank">friction effects</a> have produced insignificant pressure drops, proving that Dimpled-Protruded tubes effectively improve forced-convecting heat transfer.</p> <p> </p>