Enhancement of heat transfer and hydrodynamic performance in a double tube heat exchanger using transverse and helical turbulators with nanofluid

Abstract Double tube heat exchangers (DTHEs) are widely used in industrial thermal systems, where improving heat transfer efficiency is critical for energy savings. This numerical study investigates the thermal–hydraulic performance of transverse and helical turbulator inserts with different rib geometries (rectangular, triangular, oval, and trapezoidal) used in combination with a water-based SiO 2 nanofluid in a counterflow DTHE. Steady-state laminar simulations were performed in ANSYS Fluent for Reynolds numbers between 400 and 2000. The results show that helical turbulators significantly outperform transverse designs, with the triangular helical turbulator achieving up to a 565% increase in the Nusselt number compared to pure water without inserts, while transverse trapezoidal turbulators reached a maximum enhancement of 470%. Owing to enhanced swirl generation and boundary-layer disruption, helical turbulators also yielded superior thermal–hydraulic performance, achieving a maximum performance evaluation criterion (PEC) of 3.17, compared to 1.9 for transverse configurations. These findings demonstrate the effectiveness of helical turbulator designs combined with nanofluids for improving DTHE performance in laminar-flow industrial applications.