To enhance the heat transfer efficiency of heat exchangers，a synergistic method combining helical twisted tapes with nanofluids is proposed，and the thermal performance of this composite enhancement approach is investigated.Using Al₂O₃‑H₂O nanofluid as the working medium，key thermophysical properties （density，specific heat，viscosity，and thermal conductivity） are calculated based on classical nanofluid models.A 3D numerical model is established via computational fluid dynamics （CFD） to simulate flow and heat transfer characteristics in heat exchange tubes with inserted twisted tapes，validated against experimental data from literature （maximum relative error：10.9%）.Comparative analysis shows that the composite nanofluid‑twisted tape configuration increases the surface heat transfer coefficient by 35.18% compared to the plain tube with pure water，albeit with a 576 Pa pressure drop increase.The study reveals coupling effects of nanoparticle volume fraction and mass flow rate：as the volume fraction rises from 0.5% to 4%，the Nusselt number （Nu） decreases from 57.1 to 51.5 due to viscosity‑induced convection suppression.When mass flow increases from 0.1 kg/s to 0.4 kg/s，the Nu number enhancement of twisted tape tubes over plain tubes expands from 4.3% to 11.7%，demonstrating synergistic mechanisms between secondary flow and nanoparticle thermal transport under high‑flow conditions.These findings provide theoretical support for designing high‑efficiency heat exchangers.