摘要：Different volume concentrations (1.2, 0.6, 0.3 wt%) of Fe3O4/water nanofluids and for different Reynolds number (Re) varying from 2180 to 9160 were used experimentally. The aim of work is to study the effect of applying various magnetic field intensity 15.1, 30.3, 45.5 mT on heat transfer enhancement in a horizontal pipe heated with constant heating flux of 420 W. Results showed that Nusselt number (Nu) increases with increasing Re for the nanofluids and water regardless the presence or absence of the magnetic field. Also, higher values were obtained than water. The average increase in Nu for Fe3O4-nanofluids is 16.7% relative to water when the magnetic field is not applied. However, the average increase in heat transfer coefficient and Nusselt number are 9.4%, 26.1%, 31.3% and 8.8%, 13.1%, and 23.9% in the presence of magnetic field (Φ=15.5,30.3,45.5)mT compared to the absence of magnetic field and base fluid water, respectively. Furthermore, pressure drop increases with the increase of Reynolds number and magnetic field strength. It can be concluded that the magnetic field has a big effect on the thermal transfer performance of Fe3O4/water nanofluid when compared with the thermal motion of magnetic nanoparticles. Finally, it is found that the performance factor is above unity in the presence and absence of magnetic field strength. This means that Nusselt number enhancement is higher than friction changes, which indicates the applicability of the heated pipe in the improvement of heat transfer. These results can be useful for enhancing heat transfer in many engineering applications such as heat exchangers, medical devices, and electronic devices.
关键词：Nanofluid (Fe3O4/water-ethanol);Nusselt number;volume concentration;heat transfer;magnetic field
