AC Dielectric Strength of Mineral Oil-Based Fe3O4 and Al2O3 Nanofluids

Abstract

This paper deals with an experimental study of the influence of conductive (Fe 3 O 4 ) and insulating (Al 2 O 3 ) nanoparticles at various concentrations on the dielectric strength of transformer mineral oil. The method of preparation and characterization of these nanofluids (NFs) through the measurements of zeta potential, the real and imaginary parts of dielectric permittivity as well as the concentration and size of nanoparticles using scanning electron microscope images of nanoparticles powders and energy dispersive x-ray spectroscopy analysis are presented. Experimental findings reveal that these two types of nanoparticles materials significantly improve AC breakdown voltage and the magnitude of this enhancement depends on the nanoparticle concentration, and the size and nature (material) of nanoparticles. For a given type of nanoparticle, the effect is more marked with the smallest nanoparticles. The conductive nanoparticles offer higher enhancement of dielectric strength compared with insulating nanoparticle based nanofluids. With Fe 3 O 4 , the breakdown voltage (BDV) can exceed twice that of mineral oil and it increases by more than 76% with Al 2 O 3 . The physicochemical mechanisms implicated in this improvement are discussed. Energies 2018, 11, 3505 2 of 13This cooling property (heat transfer) was at the origin of NFs' development. Nowadays, NFs are used in several fields, like electronics (chips, electronic circuitry components); transportation (the cooling systems of heavy power machines and heat generation parts of vehicles); heating buildings and reducing pollution; nuclear cooling systems; space and defense (space stations and aircrafts); and solar absorption for heat-transfer performance. Indeed, they have preferable better thermal characteristics (thermal diffusivity, thermal conductivity, convective coefficient of heat transfer) than the base fluids. These strongly depend on properties and the volume fraction of the added nanomaterial [7,8]. Furthermore, for a given particles volume, the contact area of the solid-liquid surface between nano-size particles and the suspension fluid is greater than that for micro-size particles. Therefore, the shape and size of particles has a clear impact on heat transfer and thermal conductivity characteristics [9][10][11].The volume fraction of particles (concentration), their shape and size, and the surface contact area between particles and liquid are major parameters that influence not only the thermal properties as indicated above, but also have a very great influence on the dielectric properties of composite materials.

DC Breakdown Voltage of Synthetic Ester Liquid-Based Nanofluids

“…Indeed, hypothesis test of compliance of the average DC-BDV of investigated nanofluids complies totally with normal distribution while there is an exception as concerns the conformity with Weibull distribution that is SE/Fe 3 O 4 at 0.2 g/L. It should be noted that in the case of AC, the addition of the three investigated NPs increases the AC-BDV of the same SE; and that the highest AC-BDV was obtained using Fe 3 O 4 conducting nanoparticles of size 50 nm at a concentration 0.4 g/L; the improvement was approximately 48% with respect to the SE alone [19]. As for SiO 2 (50 nm), the most significant improvement in AC-BDV was approximately 32% for a concentration of 0.4 g/L.…”

“…The objective is to compare the dielectric strengths in DC with those already obtained in AC, for the same NFs (using the same base oil) with the same NPs and at the same concentrations. The used methodology and experimental techniques for preparing NFs were described in previous works [18,19]. This include the distribution of the various nanoparticles which was measured by using a particle size analyzer (NanoPlus, Particulate Systems, USA); scanning electron microscope (SEM) images; and energy dispersive x-ray spectroscopy (EDS) analysis.…”

Application of Water Tank Employing Smart Sensor for Thermal?Electric Energy Conversion on Vehicles

“…These studies on the modeling and analysis of thermoelectric modules have improved the effectiveness in predicting the expected power generation results when designing thermoelectric power generation systems. (8,9)…”

Statistical Investigation of Lightning Impulse Breakdown Voltage of Natural and Synthetic Ester Oils-Based Fe3O4, Al2O3and SiO2Nanofluids

“…Indeed, the addition of some NPs considerably improve the thermal properties of liquids; nanofluids (NFs) are commonly used for cooling of various devices and systems [6]- [8]. However, according to recent studies, the addition of some NPs also enhances the AC breakdown voltage (AC-BDV) of insulating liquids and especially that of MO-based Fe 3 O 4 nanofluids [9]. In the case of esters, the AC-BDV can also be improved but to a lesser degree than that of MO [10], [11].…”