Experimental investigations on transport properties of magnetic fluids

Li, Qiang; Xuan, Yimin; Wang, Jian

doi:10.1016/j.expthermflusci.2005.03.021

Cited by 265 publications

(111 citation statements)

References 11 publications

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“…Unfortunately, a direct comparison of ‖ , ⊥ with ‖ , ⊥ is not possible due to the use of different kind of sensors and heat transfer phenomena. Qualitatively, this change in ⊥ may be associated with effect of on CoFe 2 O 4 NFs, which reflects an increase in viscosity due to coherent interaction between NPs with structure formation [7].…”

Section: Resultsmentioning

confidence: 99%

“…However, none of the authors gives an explanation of the mechanism for these suppressed thermal properties and possibilities to enhance it with the application of . For example, Fe NPs in base fluid were found to exhibit enhanced at applied , and studies with varying directions of applied indicated that this could be associated with a chain like structure formation involving field gradient parallel to thermal gradient, analogous to the anisotropic transport properties of magnetorheological fluids [7][8][9]. Similarly, Lajvardi et al [10] have reported that enhancement in convective heat transfer performance of 2 ISRN Nanotechnology Fe 3 O 4 based ferrofluid under the application of magnetic field.…”

Section: Introductionmentioning

confidence: 95%

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Experimental Investigation of Thermal Conductivity and Effusivity of Ferrite Based Nanofluids under Magnetic Field

Singh¹,

Raykar

2013

ISRN Nanotechnology

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We investigate the effect of magnetic field ( ) on the thermal conductivity ( ) and effusivity ( ) of cobalt ferrite based nanofluids having different concentrations ( ). Cobalt ferrite nanoparticles (NPs) have been synthesized using the microwave assisted method. At high volume fraction of cobalt ferrite nanoparticles in water ( > 0), both thermal parameters have been found to be suppressed relative to and of water in the absence of . However, it is seen that percentage values of the effusivity in perpendicular field direction show negative to positive variation, and thermal conductivity in parallel field direction shows negative to zero variation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Experimental Investigation of Thermal Conductivity and Effusivity of Ferrite Based Nanofluids under Magnetic Field

Singh¹,

Raykar

2013

ISRN Nanotechnology

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“…This provided us with a good starting point, as our composite layers had a larger thermal conductivity than that of the resin. It is worth to mention that this kind of enhancement in the thermal properties, due to the anisotropic formation of chain-like aggregates of particles with higher conductivity than the supporting material, has also been observed in magnetic fluids under the action of applied fields [8,9,10].…”

Section: Interface Thermal Resistancementioning

confidence: 99%

“…It is worth to mention that some advances have been made in this direction with magnetic fluids, as their thermal properties can be controlled with the concentration of particles and the application of magnetic fields with different strengths. In this kind of fluids, it has been observed that the development of chains by the embedded particles greatly enhances their thermal conductivity in the direction of the chains [8,9,10,11,12].…”

Section: Introductionmentioning

confidence: 99%

Thermal properties of composite two-layer systems with a fractal inclusion structure

Reyes-Salgado¹,

Dossetti²,

Bonilla-Capilla³

et al. 2014

J. Phys. D: Appl. Phys.

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Abstract. In this work, we study the thermal transport properties of platelike composite two-layer samples made of polyester resin and magnetite inclusions. By means of photoacoustic spectroscopy and thermal relaxation, their effective thermal diffusivity and conductivity were experimentally measured. The composite layers were prepared under the action of a static magnetic field, resulting in anisotropic inclusion structures with the formation of chains of magnetite particles parallel to the faces of the layers. In one kind of bilayers, a composite layer was formed on top of a resin layer while their relative thickness was varied. These samples can be described by known models. In contrast, bilayers with the same concentration of inclusions and the same thickness on both sides, where only the angle between their inclusion structures was systematically varied, show a nontrivial behaviour of their thermal conductivity as a function of this angle. Through a lacunarity analysis, we explain the observed thermal response in terms of the complexity of the interface between the layers.

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“…7 Formation of these structures, in particular, ordered chains or columnar structures in ferrofluids as a result of an applied field, leads to a change in the macroscopic properties of the medium, 8,9 while thermodynamic properties such as effective heat capacity remain unaffected by these heterogeneous structures. 10 For instance, magnetization of ferrofluid increases with the growth of chains, 2,11-14 viscosity abruptly increases, 1,2,15 thermal conductivity is enhanced if the field direction is parallel to temperature gradient, [16][17][18][19][20] and optical properties become strongly anisotropic. 1,[21][22][23] There are several examples of successful and prospective applications of self-assembled or field-assisted magnetic nanoparticles from technical applications to medical ones: in data storage, electronic devices, sensors, rotating shaft seals, hydrostatic and hydrodynamic bearings, magnetoacoustic transducers, vibration isolation and inertia damping systems, thermal systems, medical diagnostics, therapy and drug delivery, biophysical studies, and magnetic biosensing.…”

Section: Introductionmentioning

confidence: 99%

Direct observations of field-induced assemblies in magnetite ferrofluids

Mousavi

Khapli

Kumar

2015

Journal of Applied Physics

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Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size 10 nm) is studied with an emphasis on examining the effects of particle concentration (/) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, / ¼ 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H ¼ 0.05-0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity. V C 2015 AIP Publishing LLC.

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Experimental investigations on transport properties of magnetic fluids

Cited by 265 publications

References 11 publications

Experimental Investigation of Thermal Conductivity and Effusivity of Ferrite Based Nanofluids under Magnetic Field

Experimental Investigation of Thermal Conductivity and Effusivity of Ferrite Based Nanofluids under Magnetic Field

Thermal properties of composite two-layer systems with a fractal inclusion structure

Direct observations of field-induced assemblies in magnetite ferrofluids

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