Investigation of convective heat transfer in helically corrugated tubes with inserts using nanofluids

This study delves into the synergistic impacts of corrugated configurations, inserts, and nanofluids on both the Nusselt number (Nu) and the friction factor (f) under turbulent flow conditions. Investigating the impact of corrugation pitch and height on Nu and f, five helically corrugated tubes (HCTs) featuring different pitch and height dimensions are utilized. Two spiraled rod inserts (SRIs) featuring distinct pitch (p(i)) dimensions are employed. A nanofluid is created by dispersing Al2O3 nanoparticles within deionized (DI) water, at volume concentrations (VCs) of 0.25% and 0.5%. The results reveal that (i) the introduction of nanoparticles into water bring about a boost in the Nu. The Nu experiences a 15.2% rise when 0.5% VC nanofluid is used in comparison to water within a plain tube. (ii) The existence of corrugations on the inner side of the tube and the incorporation of inserts into the tube accelerate the rate of heat transfer. (iii) When using nanofluids with 0.5% VC, the most significant improvements are seen in the Nu, which surges by 83.43%, and the f, which goes up by 81.1%. These enhancements are achieved by fitting a low-pitch insert inside a HCT with a large corrugation height (h(c)) and a small corrugation pitch (p(c)). The novelty and uniqueness of the investigation is the concurrent use of corrugated tubes, inserts, and nanofluids to enhance heat transfer. This novel combination provides opportunities for increased efficiency, reduced costs, and improved performance in various industrial and engineering applications.