Effect of magnetic field on laminar forced convective heat transfer of MWCNT–Fe3O4/water hybrid nanofluid in a heated tube.

A numerical investigation is carried out to assess the hydrothermal performance of a water-based hybrid nanofluid containing both Fe3O4 (magnetite) nanoparticles and carbon nanotubes (CNTs) in a heated tube in the presence of a constant non-uniform magnetic field. The magnetic field is created by three pairs of permanent magnets. The effects of Reynolds number, magnetite, and CNT volume concentrations as well as magnetic field strength are investigated. The acquired data for the case of without magnetic field confirmed higher values of heat transfer and pressure drop as a result of utilizing nanofluid compared with water. Additionally, it was found that the Nusselt number and pressure drop of the studied nanofluid samples increase significantly under the magnetic field. Moreover, the influence of magnetic field increases with an increase in the nanoparticle concentrations and magnetic field strength and decrease in the Reynolds number. The maximum increments of 109.31% and 25.02% in comparison with the case of without field were obtained in the average Nusselt number and pressure drop for hybrid nanofluid containing 0.9% magnetite and 1.35% CNT at Reynolds number of 500. [ABSTRACT FROM AUTHOR]