Laminar flow and heat transfer of magnetic nanofluid in a cylindrical tube under constant magnetic fields

18th International Nanoscience and Nanotechnology Conference, İstanbul, Türkiye, 26 - 28 Ağustos 2024, sa.14, ss.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.