Influence of Wire-Coil Inserts and Graphene Oxide Concentration on Heat Transfer Augmentation

Abstract Heat transfer augmentation has been developed and implemented in response to the necessity of improving the thermal efficiency of heat exchangers, thereby conserving energy, reducing costs, and minimizing material usage. This study investigated thermal performance utilizing a wire-coil insert and graphene oxide nanofluid flowing through a circular tube with constant heat flux. The investigation employed various Reynolds numbers ranging from 5000 to 18,000 and graphene oxide with nanoparticle concentrations of 0.025, 0.05, 0.075, and 0.1 wt%. Wire-coil inserts with different pitch-to-coil diameter ratios (P/D = 1, 1.5, and 2) were utilized in the experiments. The structure and molecular behavior of graphene oxide nanoparticles were characterized using X-ray diffraction and scanning electron microscopy. The Nusselt number and friction factor increased with the utilization of the graphene oxide nanofluid and wire-coil inserts. A maximum thermal performance value of 1.21 was observed at the 0.5 wt% concentration of graphene oxide nanofluid and a P/D ratio of 1.5 for the wire-coil insert. These findings highlight the potential of this combined approach to enhance the performance of heat exchangers, offering practical and scalable solutions for energy-efficient applications while paving the way for further optimization in nanofluid properties and coil geometries.