Numerical Investigation of Hydrothermal Performance Enhancement Using Modified Twisted Tape Having a Curved and Concave Cross-section Inserted in a Horizontal Tube

The present study investigated the enhancement of convective heat transfer in horizontal tubes using twisted tape inserts, particularly emphasizing the influence of modifications to their geometrical configurations. Three twisted tape models were designed using SolidWorks: a plain tape, a tape with curved edges, and a tape with curved edges and holes. Two twist ratios were considered, namely TR1 = 6.666 and TR2 = 5. Computational Fluid Dynamics (CFD) simulations were performed to evaluate the velocity and temperature fields, Nusselt number, and friction factor over a Reynolds number range of 15,000–25,000. The results indicate that employing twisted tape with curved edges and perforations leads to the greatest enhancement in heat transfer. Specifically, the Nusselt number increases from 410 for curved edges without perforations to 460, whereas the plain tape achieves 380 at Re = 25,000 and TR2. The tape with curved edges (without holes) demonstrated the most favorable improvement in friction factor, attaining a value of 0.024 versus 0.029 for the plain tape, corresponding to a 20.8% reduction. As a result, the performance evaluation factor achieved a peak value of 1.24, indicating a 30.5% improvement. These findings demonstrated that optimized twisted tape geometries significantly enhanced heat transfer performance while maintaining reasonable pressure drop penalties. This highlights their potential applicability in thermal system design, particularly in compact and energy-efficient heat exchangers.