Experimental Investigation On The Convective Heat Transfer Of Fe₃O₄/water Nanofluids Under Magnetic Field

Nanofluids presented excellent heat transfer performance,however,there were still some problems when being used in the heat exchanger.The motion of magnetite nanoparticles could be controlled by the applied magnetic field,which offered a new research direction for improving the stability of nanofluids and attracted many researchers.The effect of the direction,intensity and arrangement of magnetic field on heat transfer performance of Fe₃O₄/Water nanofluids with various nanofluid concentrations and inlet temperatures was studied.The experimental results showed that the convective heat transfer coefficient of Fe₃O₄/Water nanofluids increased with the concentration and temperature,and a maximum increase was 5.6%at the volume concentration of 3%and the inlet temperature of 40?.The heat transfer coefficient of the convective heat transfer of Fe₃O₄/Water nanofluids was enhanced in the perpendicular magnetic field and the maximum increase were 5.2%and 9.2%,respectively,under uniform and gradient magnetic fields.The non-dimensional analysis about the energy conservation equation of Fe₃O₄/Water under the applied magnetic field was carried out,and the calculation results showed that the magnetic force acting on the nanoparticles was much larger than the Brownian motion force and thus the magnetic force dominated the heat transfer.The experimental results agreed well with the non-dimensional analysis.The magnetite nanoparticles aggregated in the direction of the magnetic field and formed as a thermal channel connecting the pipe wall and the main flow of nanofluids,which accounted for the enhancement.The motion of magnetite nanoparticles under the effect of magnetic force was another reason.