Twisted-tape inserts of rectangular and triangular sections in turbulent flow of CMC/CuO non-Newtonian nanofluid into an oval tube

Purpose - This paper aims to study numerically the non-Newtonian solution of carboxymethyl cellulose in water along with copper oxide nanoparticles, which fl ow turbulently through twisted smooth and fi nned tubes. Design/methodology/approach - The twisted-tape inserts of rectangular and triangular sections are investigated under constant wall heat fl ux and the nanoparticle concentration varies between 0% and 1.5%. Computational fl uid dynamics simulation is fi rst validated by experimental information from two test cases, showing that the numerical results are in good agreement with previous studies. Here, the impact of nanoparticle concentration, tube twist and fi ns shape on the heat transfer and pressure loss of the system is measured. It is accomplished using longitudinal rectangular and triangular fi ns in a wide range of prominent parameters. Findings - The results show that fi rst, both the Nusselt number and friction factor increase with the rise in the concentration of nanoparticles and twist of the tube. Second, the trend is repeated by adding fi ns, but it is more intense in the triangular cases. The tube twist increases the Nusselt number up to 9%, 20% and 46% corresponding to smooth tube, rectangular and triangular fi ns, respectively. The most twisted tube with triangular fi ns and the highest value of concentration acquires the largest performance evaluation criterion at 1.3, 30% more efficient than the plain tube with 0% nanoparticle concentration. Originality/value - This study explores an innovative approach to enhancing heat transfer in a non- Newtonian nanofluid fl owing through an oval tube. The use of twisted-tape inserts with rectangular and triangular sections in this specific configuration represents a novel method to improve fl uid fl ow characteristics and heat transfer efficiency. This study stands out for its originality in combining non-Newtonian fl uid dynamics, nanofluid properties and geometric considerations to optimize heat transfer performance. The results of this work can be dramatically considered in advanced heat exchange applications.