Experimental study on effect of employing twisted conical strip inserts on thermohydraulic performance considering geometrical parameters

• Published in: International journal of thermal sciences 2020-03, Vol.149, p.106178, Article 106178
• Main Authors: Bahiraei, Mehdi, Gharagozloo, Khashayar, Moayedi, Hossein
• Format: Article
• Language: English
• Subjects: Experimental study; Flow mixing; Heat transfer enhancement; Pumping power; Thermohydraulic performance; Twisted conical strip inserts
• ISSN: 1290-0729; 1778-4166
• DOI: 10.1016/j.ijthermalsci.2019.106178

In this study, the thermohydraulic characteristics for the water flow inside a circular pipe enhanced by the twisted conical strip inserts are experimentally assessed. The conical strip inserts are made by stereolithography 3D printer. The effects of geometric features including the twist angle and pitch ratio (i.e., the ratio of pitch to inner pipe diameter), well as Reynolds number are evaluated. Owing to intensification of the flow mixing and disruption in the boundary layers, the pipe enhanced by the conical inserts has greater friction coefficient and Nusselt number than the smooth pipe. Meanwhile, the Nusselt number and friction coefficient rise by decreasing each of the parameters of twist angle and pitch ratio and by increment of the Reynolds number. The Nusselt number increment due to employing the conical inserts is greater at the lower Reynolds numbers. One of the most important causes of the increase in the pressure loss is the existence of dead flow zones behind the conical strip inserts, which these zones decrease by increasing the pitch ratio and twist angle. Furthermore, the performance evaluation criterion is greater than 1 for Reynolds numbers of 460 and 630, which indicates that the merit of applying the twisted conical inserts is better in this range of the Reynolds number. •Studying thermohydraulic features in tube fitted with twisted conical strip insert.•The conical strip inserts are made by stereolithography 3D printer.•Tube with inserts has higher Nusselt number and friction factor than plain tube.•Nusselt number increment due to using inserts is greater at lower Reynolds numbers.•Performance criterion is greater than 1 for Reynolds numbers of 460 and 630.