Synergistic impact of wavy tape and wire coil turbulators on the thermo-hydraulic performance of tubular heat exchangers

A comprehensive experimental study was conducted to evaluate the thermal and hydraulic performance of multiple turbulator configurations within a Reynolds number range of 2000–11,000. The experimental rig was validated against established correlations for Nusselt number and friction factor, demonstrating strong agreement and confirming its robustness for heat transfer and fluid flow investigations. Results indicate that the introduction of a wavy tape increases pressure drop by 18 – 30 folds due to sinusoidal and cross-flow–induced turbulence, while the addition of central holes mitigates this effect to the extent of 1 – 10% by partially damping turbulence. The wavy tape–wire coil combination exhibited comparable pressure drops at low Reynolds numbers, but beyond Re ≈ 7000, the synergistic interaction of sinusoidal vortices and induced swirl led to a pronounced rise. Friction factor trends confirmed the expected decline with increasing Reynolds number, with all turbulators showing higher values than the plain tube, and the wavy tape–wire coil configuration yielding the highest resistance. Heat transfer enhancement was evident across all turbulators, with the wavy tape–wire coil combination consistently outperforming others by maximizing turbulence. Nusselt number trends mirrored the convective coefficient behaviour, with the maximum enhancement observed in the transition region as 368%, which is narrowed down to 280% in the turbulent region compared to plain tube. It highlights the dependence of optimal turbulator selection on the operating regime. Performance evaluation criteria (PEC) analysis revealed that while PEC-I peaked in the laminar to early transition regime, PEC-II indicated turbulent conditions as more favourable for pumping power–sensitive applications. PEC-III established the wavy tape–wire coil combination as the most effective overall, providing a balance of thermal and hydraulic benefits. Importantly, this configuration achieves high performance (PEC-III = 1.65) while retaining geometric simplicity and economic viability, offering a practical alternative to more complex turbulator designs.