Semnan University Press Journal of Heat and Mass Transfer Research 2345-508X 13 2 2026 06 01 Improvement of Energy, Exergy Efficiency and PEC Index in a Heat Exchanger Equipped with Turbulators under the Effect of a Magnetic Field بهبود بازده انرژی و اگزرژی و شاخص PEC در یک مبدل گرمایی مجهز شده به توربولاتور تحت تاثیر میدان مغناطیسی 193 206 9849 10.22075/jhmtr.2025.36432.1672 EN Alireza Aghaei Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran Alireza Mirzaei Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran Abolfazl Fattahi Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran Journal Article 2025 01 04 A double-tube heat exchanger equipped with vortex generators is simulated under the influence of a magnetic field. The internal tube of this heat exchanger is equipped with blade-type vortex generators with various geometrical shapes. A magnetic field is employed to enhance thermal efficiency in the double-tube heat exchanger, with Hartmann numbers ranging from 35 to 155. The applied hybrid nanofluid is composed of Syltherm 800, iron oxide, and graphene oxide at volume fractions (φ) of 0, 1.75, and 3.75%. The study is conducted under steady-state conditions using a two-phase model with Reynolds number ranging from 25,000 to 55,000, utilizing the k-epsilon turbulence model. The results indicate that as the Re increases, the convective heat transfer coefficient rises. The maximum increase in the Nusselt number is observed in the heat exchanger equipped with vortex generators of Sample 3, whereas the minimum value occurs in the bare heat exchanger. Additionally, as the Hartmann number increases from 35 to 155, the exergy efficiency also rises. Exergy efficiency increases with Reynolds number up to 35,000 and then decreases. It is also found that the application of a magnetic field maximizes the exergy efficiency at a Re of 35,000 and Hartmann number of 155 for the heat exchanger equipped with Sample 3 vortex generators. https://jhmtr.semnan.ac.ir/article_9849_e2c967dc22f2ea49fa16f04cd1ae00bc.pdf