Iranian Journal of Chemical Engineering (IJChE)

Abstract In this study, the effect of the presence of a magnetic field (MF) on the thermal conductivity of the nanofluid (NF) ( ) containing spinel ferrite nanoparticles (NPs) (MFe₂O₄, M=Fe, Co) was investigated. CoFe₂O₄ NPs were concentrated by the coprecipitation method. Both NPs were characterized by SEM, EDX, XRD, and VSM. The thermal conductivity was investigated and compared in the presence and absence of an MF. In addition to the intensity of MF (100, 200, 300, and 400 G), the effect of the concentration of NPs (from 0.25 to 2 Vol%) on  at a constant temperature of 25 °C was investigated. According to the results, in the absence of MF, the  of CoFe₂O₄/water ferrofluid (FF) was higher than that of Fe₃O₄/water FF in different concentrations. Furthermore, as the intensity of the MF increased, the  of both Fe₃O₄/water and CoFe₂O₄/water FFs increased. This increase was more observed for the FFs containing Fe₃O₄ NPs. At the highest concentration (2 Vol%), with the increase of MF up to 400 G, the  of Fe₃O₄/water has increased by about 3.2%, while this increase was about 1.8% for CoFe₂O₄/water. Increasing the volume percentage of NPs also had a positive effect on the thermal conductivity coefficient. Finally, according to the obtained results, correlations were presented to predict the  of both FFs according to the intensity of the MF and the concentration of NPs. The proposed correlations had a satisfactory accuracy with R² values of 0.98 for both FFs.

Abstract Wind energy is used to rotate a magnetic turbine in order to remove heat from the surface of a photovoltaic (PV) panel. A three-bladed turbine, which rotates with wind energy, has rotational motion underneath the studied PV panel in order to move Magnetic Nano-Particles (MNPs). In addition, effects of the magnetic field strength (B=450-830 mT), rotational velocity of the magnetic turbine (ω), and the concentration of MNPs (ϕ) on the heat removal from the PV panel area were investigated. Results showed that heat removal from PV panel was intensified by motion of pinned MNPs in the ferrofluid via the exerted external force of magnetic field. Concurrent application of available magnetic field along with ferrofluid led to 7.6-24 % temperature reduction for a PV panel. Furthermore, the produced electrical energy of the PV panel was augmented between 2.55-3.13 W depending on ϕ, ω, and B. Moreover, the impact of ω on cooling performance was also investigated, and a significant enhancement to generated power was observed. Eventually, the maximum amount of the produced power (3.13 W), maximum power enhancement percentage (32.63 %), and thermal efficiency (24 %) were achieved for B=830 mT, ω=50 cycles/min, and ϕ=0.05 (w/v).