Transformer oil-based magnetic nanofluid with high dielectric losses tested for cooling of a model transformer

Rajňák, Michal; Τimko, M.; Kopčanský, P.; Paulovičová, K.; Kuchta, Jozef; Franko, Marek; Kurimský, Juraj; Dolník, Bystrík; Cimbala, Roman

doi:10.1109/tdei.2019.008047

Cited by 29 publications

(14 citation statements)

References 21 publications

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“…Furthermore, at room temperature, the magnetization exhibits zero hysteresis, indicating the superparamagnetic behavior of magnetic nanoparticles. The blocking regime is reflected in the remarkable coercivity detected at 2 K [15]. Figure 1, b shows the well-know temperaturedependent behavior of the magnetization measured on a magnetic nanofluid with iron oxide nanoparticles in ZFC and FC regimes.…”

Section: Characterization Of Magnetic Fluidsmentioning

confidence: 82%

“…Thus, this fact is often utilized in revealing the . Reproduced, with modification, from [15] particle size distribution when measuring the temperature dependent magnetization of magnetic fluids in the so-called zero field cooling (ZFC) and field cooling (FC) regimes ( Fig. 1, b).…”

Section: Characterization Of Magnetic Fluidsmentioning

confidence: 99%

“…1, b). On the other hand, one can obtain important information from magnetization curves on the magnetic particle volume fraction in a fluid, as well as the magnetic diameter of the nanoparticles, as reported in various studies on magnetic fluids [14][15][16]. From Fig.…”

Section: Characterization Of Magnetic Fluidsmentioning

confidence: 99%

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Modification of Diamagnetic Materials Using Magnetic Fluids

et al. 2020

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Magnetic fluids (ferrofluids) have found many important applications in various areas of biosciences, biotechnology, medicine, and environmental technology. In this review, we have summarized the relevant information dealing with a magnetic modification of diamagnetic materials using different types of ferrofluids. Special attention is focused on a magnetic modification of plant-derived biomaterials, microbial and microalgal cells, eukaryotic cells, biopolymers, inorganic materials, and organic polymers. Derivatization is usually caused by the presence of magnetic iron oxide nanoparticles within the pores of treated materials, on the materials surface or within the polymer gels. The obtained smart materials exhibit several types of responses to an external magnetic field, especially the possibility of the selective magnetic separation from difficult-to-handle environments by means of a magnetic separator. The ferrofluid-modified materials have been especially used as adsorbents, carriers, composite nanozymes or whole-cell biocatalysts.

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Section: Characterization Of Magnetic Fluidsmentioning

confidence: 82%

Section: Characterization Of Magnetic Fluidsmentioning

confidence: 99%

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Modification of Diamagnetic Materials Using Magnetic Fluids

et al. 2020

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“…It is well-known that particles can enhance the properties of liquids serving as coolants e.g., in transformers. Additionally, magnetic particles were used to enrich cooling transformer oils because they may improve thermal conductivity [14], so the elements of the transformer can be better protected against over-heating. In the case of Pickering droplets capsulated in a solid magnetic particle shell, the situation can be opposite as the heat transfer through the emulsion with droplets coated by magnetic particles and immersed in surrounding liquid is hindered.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Particle Shell on Cooling Rates in Oil-in-Oil Magnetic Pickering Emulsions

Bielas

Józefczak

2020

Materials

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Pickering emulsions (particle-stabilized emulsions) are usually considered because of their unique properties compared to surfactant-stabilized emulsions including better stability against emulsion aging. However, the interesting feature of particle-stabilized emulsions could be revealed during their magnetic heating. When magnetic particles constitute a shell around droplets and the sample is placed in an alternating magnetic field, a temperature increase appears due to energy dissipation from magnetic relaxation and hysteresis within magnetic particles. We hypothesize that the solidity of the magnetic particle shell around droplets can influence the process of heat transfer from inside the droplet to the surrounding medium. In this way, particle-stabilized emulsions can be considered as materials with changeable heat transfer. We investigated macroscopically heating and cooling of oil-in-oil magnetic Pickering emulsions with merely packed particle layers and these with a stable particle shell. The change in stability of the shell was obtained here by using the coalescence of droplets under the electric field. The results from calorimetric measurements show that the presence of a stable particle shell caused a slower temperature decrease in samples, especially for lower intensities of the magnetic field. The retarded heat transfer from magnetic Pickering droplets can be utilized in further potential applications where delayed heat transfer is desirable.

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“…Thus, various nanofluids have been synthesized with the aim of improving the cooling and insulating properties of the base dielectric liquid. Besides the conventional nanoparticles, such as TiO 2 or Al 2 O 3 , these improvements have been achieved also with graphene nanosheets [3,4], fullerene [5], or magnetic nanoparticles (MNPs) [6,7]. The stable dispersions of MNPs in TO (well-known as magnetic nanofluids or ferrofluids) have an advantage over other nanofluids due to the controllability of thermal, dielectric, and viscous properties by an external magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Field Effect on Thermal, Dielectric, and Viscous Properties of a Transformer Oil-Based Magnetic Nanofluid

Rajňák

Dolník

et al. 2019

Energies

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Progress in electrical engineering puts a greater demand on the cooling and insulating properties of liquid media, such as transformer oils. To enhance their performance, researchers develop various nanofluids based on transformer oils. In this study, we focus on novel commercial transformer oil and a magnetic nanofluid containing iron oxide nanoparticles. Three key properties are experimentally investigated in this paper. Thermal conductivity was studied by a transient plane source method dependent on the magnetic volume fraction and external magnetic field. It is shown that the classical effective medium theory, such as the Maxwell model, fails to explain the obtained results. We highlight the importance of the magnetic field distribution and the location of the thermal conductivity sensor in the analysis of the anisotropic thermal conductivity. Dielectric permittivity of the magnetic nanofluid, dependent on electric field frequency and magnetic volume fraction, was measured by an LCR meter. The measurements were carried out in thin sample cells yielding unusual magneto-dielectric anisotropy, which was dependent on the magnetic volume fraction. Finally, the viscosity of the studied magnetic fluid was experimentally studied by means of a rheometer with a magneto-rheological device. The measurements proved the magneto-viscous effect, which intensifies with increasing magnetic volume fraction.

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Transformer oil-based magnetic nanofluid with high dielectric losses tested for cooling of a model transformer

Cited by 29 publications

References 21 publications

Modification of Diamagnetic Materials Using Magnetic Fluids

Modification of Diamagnetic Materials Using Magnetic Fluids

The Effect of Particle Shell on Cooling Rates in Oil-in-Oil Magnetic Pickering Emulsions

Magnetic Field Effect on Thermal, Dielectric, and Viscous Properties of a Transformer Oil-Based Magnetic Nanofluid

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