A numerical study has been conducted to investigate the transport mechanism of natural convection in a C-shaped enclosure filled with water-Al2O3 nanofluid for various pertinent parameters. The effects of the volume fraction of the Al2O3 nanoparticles, Rayleigh number, and radius of inserted cylindrical pins on the temperature, velocity, heat flux profiles and average Nusselt number have been investigated. General correlations for the effective thermal conductivity and viscosity of nanofluids are used for this analysis. The governing mass, momentum and energy equations are solved numerically with the finite volume method using the SIMPLER algorithm. The results show that addition of nanoparticle improves the heat transfer performance. Insertion of cylindrical pins of lower radius increases the average Nusselt number irrespective of Rayleigh number. But anomaly has been observed while pins of higher radius are inserted due to enormous disturbance in the fluid.
Bismuth ferrite (BiFeO3), an inorganic chemical compound, has added a new dimension to the multiferroic materials research. We previously reported the synthesis routes and improved photocatalytic properties of 10% Ti-doped BiFeO3 (BiFe0.9Ti0.1O3). In this study, we investigated the ferroelectric and ferromagnetism properties of BiFe0.9Ti0.1O3 bulk and nanoparticles and compared them with those of undoped BiFeO3 bulk ceramics. Elemental analysis was conducted to explore the chemical composition in the doped samples. The magnetic characterization and electrical measurements were performed in Vibrating Sample Magnetometer and Ferroelectric Loop Tracer respectively. Magnetization versus applied magnetic field, leakage current density, and polarization versus electric field measurements reveal improved multiferroic properties in Ti-doped bulk and nano samples compared to undoped BiFeO3 bulk.
The thermophysical properties as well as the thermal performance of a nanofluid can be altered upon varying the nanoparticle type and/or nanoparticle volume concentration. Herein, the effects of variable nanoparticle concentration on water-based TiO2, SiO2, TiC, and SiC nanofluids have been studied analytically. The dispersion effects of 1-4% nanoparticle on the single-phase forced convection heat transfer performance of the nanofluids have been investigated. The effective thermophysical properties of the nanofluids are determined adopting the general correlations. The flow velocities of the nanofluids relative to their base fluids are assumed to be constant. Mouromtseff number has been employed as a convenient figure of merit to compare the nanofluids under fully developed internal laminar and turbulent flow conditions. The results indicate an increase in effective density, thermal conductivity, and dynamic viscosity of the nanofluids. Nanofluids containing carbide suspensions exhibit superior heat transfer properties compared to those having oxide suspensions.
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