Experimental evaluation of thermal conductivity, viscosity and breakdown voltage AC of nanofluids of carbon nanotubes and diamond in transformer oil

Fontes, Douglas; Ribatski, Gherhardt; Filho, Ênio Pedone Bandarra

doi:10.1016/j.diamond.2015.07.007

Cited by 140 publications

(77 citation statements)

References 21 publications

(28 reference statements)

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“…This method is widely used to measure the conductivity of nanofluids because it minimizes natural convection due to its relative simplicity. 32 The measurement was performed with a TP-08 model probe, the temperature was equilibrated using a cooling bath, and the temperature was measured using a mercury bulb thermometer. Five measurements were made for each temperature in the range of 10 to 60 °C.…”

Section: Characterizationmentioning

confidence: 99%

Aqueous Nanofluids Based on Copper MPA: Synthesis and Characterization

et al. 2018

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The application and use of efficient cooling fluids have become increasingly important due to the increasing industrial and energy demand associated with the miniaturization of various electronic devices. The search for high-efficiency heat exchanger fluids in the early 1990s led to the development of a new class of refrigerants called nanofluids. The use of nanofluids is linked to obtaining stable colloidal dispersions which exhibit high thermal conductivity. For this purpose, the efficiency of a nanofluid will depend on the type of fluid used and the dispersed nanomaterial. In this work, a stable aqueous nanofluid based on mercaptopropionic acid-coated copper sulfide nanoparticles (Cu 2 S/MPA), synthesized by the chemical reduction method, was developed. The nanofluid presented colloidal stability in alkaline medium and an average increase of 36% in thermal conductivity for a volumetric fraction of 0.05%.

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Section: Characterizationmentioning

confidence: 99%

Aqueous Nanofluids Based on Copper MPA: Synthesis and Characterization

et al. 2018

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“…Outras pesquisas recentes já avaliaram a aplicação em fármacos, cosméticos e na medicina (FLORES, 2016). Contudo, apesar do grande potencial na intensificação da transferência de calor, essa tecnologia ainda se encontra em desenvolvimento.…”

Section: Motivaçãounclassified

“…A massa específica de uma mistura sólido-líquido pode ser obtida a partir da conservação de massa, sendo essa a forma mais correta, ou pela regra da mistura (FONTES, 2015). De acordo com Colla (2012), a massa específica de nanofluidos pode ser geralmente calculada como médias ponderadas, conhecendo as propriedades do fluido base e do material das nanopartículas.…”

Section: Massa Específica De Nanofluidosunclassified

“…Dentro do homogeneizador, o nanofluido circula dentro de uma câmara de interação na qual a pressão exercida pelos pistões sobre o líquido é controlada por uma válvula manual que indica a pressão através de um manômetro acoplado no equipamento. O processo de homogeneização é realizado pela ação de pistões que aplicam pressões que podem ir de 100 a 1600 bar (dependendo do equipamento), sendo geralmente Figura 2.24 -(a) Esquema representativo do processo de homogeneização de nanofluidos utilizando homogeneizador a alta pressão (Flores, 2016) et al, (2015), obteve uma melhor estabilidade do óxido de cobre (CuO), disperso em óleo de motor, pela aplicação do processo de moagem úmida por 3h e 300 rpm.…”

Section: Homogeneização a Alta Pressãounclassified

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Síntese e caracterização de nanofluidos para aplicação em sistemas térmicos

Oliveira¹

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iii À minha mãe Regina, exemplo de vida, força, fé e amor.Ao meu esposo Elias, companheiro, amigo e motivador de todas as minhas conquistas.E, ao progresso da ciência! iv "Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less." Marie Curie v AGRADECIMENTOSAgradeço à Deus por sempre guiar o meu caminho.À minha família pela educação e por toda a sua contribuição para o meu crescimento.Ao Prof. Dr. Enio Pedone Bandarra Filho pela confiança em mim depositada, acolhimento, oportunidade e orientação desta Tese. AbstractThe goals of this work were to study the synthesis and characterization of the thermophysical properties of various types of nanofluids in order to evaluate their application in thermal exchange systems. For this, nanofluids of aqueous base, base oil and ethylene glycol base were prepared and studied, containing six types of nanoparticles: TiO2, Ag, Cu, MWCNT, diamond and graphene. Hybrid nanoparticles (Diamond-Nickel, MWCNT-Ag, graphene-Ag) and functionalized surface MWCNT-COOH, Di-COOH and TiO2-PVA were also produced. For the structural characterization of the nanoparticles, X-ray diffraction (XRD), Raman spectroscopy and infrared (FTIR) techniques were used, as well as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images. The synthesis of the nanofluids consisted of the application of the "two-step" method, using sonication processes and high pressure homogenization to disperse the nanoparticles, using volumetric concentrations ranging from 0.00125% to 0.1%, and mass concentrations of 0.05 to 1.0 wt%, in base fluids. The thermophysical properties (thermal conductivity and viscosity) were measured experimentally in a temperature range of 10° to 60° C and an increase in both the thermal conductivity and the viscosity were observed with the increase in the volumetric fraction of nanoparticles and with the temperature. The stability of the nanofluids was evaluated by the sedimentation observation method. In general, nanofluids without stabilizers remained stable for a few weeks. The experimental results, obtained for thermal conductivity, revealed a maximum increase of 10.67% for diamond nanofluids in mineral oil with oleic acid as stabilizing agent. The maximum increase in viscosity was obtained for nanofluidos of MWCNT, being 1.6 times greater than the viscosity of the water. The results, of thermal conductivity, viscosity and specific mass, were still compared with the classic models of the literature. Thus, the studies of the synthesis and characterization of nanofluids revealed an increase of the thermal conductivity with the dispersion of nanoparticles being a promising alternative as fluids applied in processes of thermal changes.

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“…Usually, the base fluid is distilled water, 2-4 ethylene glycol, [5][6][7][8][9] or a certain oil. [10][11][12][13][14] Numerous papers on experimental and theoretical properties of nanofluids and their potential applications in the industry have been published so far. A broad field of applications of the nanofluids is in the systems related to heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

Fal

Cholewa

Gizowska

et al. 2016

Journal of Elec Materi

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This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (e 0 ) and imaginary (e 00 ) parts of the complex permittivity (e Ã ) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

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Experimental evaluation of thermal conductivity, viscosity and breakdown voltage AC of nanofluids of carbon nanotubes and diamond in transformer oil

Cited by 140 publications

References 21 publications

Aqueous Nanofluids Based on Copper MPA: Synthesis and Characterization

Aqueous Nanofluids Based on Copper MPA: Synthesis and Characterization

Síntese e caracterização de nanofluidos para aplicação em sistemas térmicos

Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

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