Self-Driven Flow Characteristic of Magnetic Nanofluids Under the Magnetic Field

Against the backdrop of the ever-expanding practical applications of magnetic nanofluids, the self-driven flow and heat transfer characteristics of water-based Fe₃O₄ magnetic nanofluids were experimentally investigated under a uniform magnetic field in the closed-loop pipeline system in this work. Specifically, Fe₃O₄ nanoparticles were synthesized using the co-precipitation method, and stable magnetic nanofluids with concentrations ranging from 0.025 wt% to 0.150 wt% were prepared using sodium citrate as a dispersant. In the presence of a magnetic field, a closed-loop system that integrates heating and cooling branches was established. Furthermore, the effects of magnetic field strength, temperature difference between the heating and cooling sections, magnetic nanofluid concentration, and pipeline length on the self-circulation flow velocity were discussed, leading to insights into the heat transfer characteristics of the magnetic nanofluid. The results showed that the circulation flow velocity increases with the increase in magnetic field strength, magnetic nanofluid concentration, and temperature difference, while it decreases with the increase in pipeline length. Correspondingly, the heat transfer coefficient between the pipeline wall and the fluid increased significantly with the increase in circulation flow velocity. The priority of factors on the thermomagnetic effect is ranked as magnetic field strength > pipeline length > temperature difference > magnetic nanofluid concentration.