18th International Nanoscience and Nanotechnology Conference, İstanbul, Turkey, 26 - 28 August 2024, no.14, pp.58
In heat transfer systems, conventional fluids such as water, oil, ethylene, and glycol often constrain
thermal performance due to their relatively low thermal conductivity. To mitigate this limitation and
elevate the heat transfer efficiency, nanofluids with enhanced thermal conductivity present a promising
alternative to conventional fluids. Among the nanofluids, the ferrofluids, distinguished by the presence
of ferromagnetic nanoparticles have shown promise in further increasing the heat transfer rates and
there are many studies on the subject in the literature [1-5]. Studies show that, the interaction between
magnetic nanoparticles and applied magnetic fields can substantially amplify forced convective heat
transfer rates. Moreover, it is also shown that the heat transfer enhancement is significantly dependent
on the properties and the distribution of the applied magnetic field along the flow line.
In this regard, this study experimentally investigates the forced convective heat transfer of water-based
ferrofluids with Fe3O4 nanoparticles, flowing in a stainless steel tube under the effect of constant
magnetic fields with varying distributions. To investigate the effect of different magnetic field
distributions on heat transfer, magnets are distributed along the flow path with two different
arrangements and a magnetic field of approximately 700 Gauss intensity is applied to the ferrofluid at
different points during the heat transfer process. The experiments are conducted for seven different
Reynolds numbers (400-1000), two different magnet arrangements (parallel and staggered) and 0.5%
nanoparticle volume fraction under constant heat flux boundary condition. Local and average Nusselt
numbers along with pressure drop values are determined and the influence of applied magnetic fields
on heat transfer performance and its interaction with other changes in parameters are discussed in detail.
This study demonstrated the positive effect of the high magnetic gradient perpendicular to the flow
generated by the staggered magnetic pole arrangement on heat transfer, with the highest improvements
in local and average Nusselt numbers obtained as 142.4% and 28.7%, respectively, under staggered
magnet arrangement.