Investigation of heat transfer properties of CuZnFe2O4-water and NiZnFe4O4-water nanofluids under magnetic field effect

The aim of the present study is to investigate the heat transfer characteristics of CuZnFe2O4-water and NiZnFe4O4-water nanofluids since there is no study in the literature examining the thermal performances and thermophysical properties of the mentioned nanofluids under an external magnetic field. Experiments were conducted utilizing nanofluids with volume concentrations of 0.5% and 1.0% in a mini-channel, maintaining consistent heat flux boundary conditions over a Reynolds number range of 300–1300. Three magnetic field intensities (22 mT, 30 mT, and 38 mT) were applied using two electromagnets arranged perpendicular to the flow direction. The results demonstrate significant improvements in the Nusselt number with the use of nanofluids, particularly when subjected to an external magnetic field, indicating enhanced heat transfer. The impact of the magnetic field on heat transport is pronounced at low Reynolds numbers and with nanofluids containing a high concentration of nanoparticles. Moreover, the intensity of the magnetic field exerts a notable positive influence. Maximum enhancements in the Nusselt number were observed for both nanofluids at a volume concentration of 1.0%, Reynolds number of 300, and a magnetic field intensity of 38 mT. Interestingly, the CuZnFe2O4-water nanofluid exhibits greater responsiveness to the magnetic field compared to the NiZnFe4O4-water nanofluid. Relative to the case without a magnetic field, the NiZnFe4O4-water nanofluid showed a maximum Nusselt number increase rate of 24.62%, while the CuZnFe2O4-water nanofluid demonstrated a higher increase rate of 39.34%.