Gravitational and Magnetic Convection in Magnetic Colloids

2005 ◽  
Author(s):  
Gennady F. Putin ◽  
Alexandra A. Bozhko
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Liquid Crystal ◽  
Magnetic Particles ◽  
Homogeneous Magnetic Field ◽  
Temperature Sensors ◽  
Localized States ◽  
Long Wave ◽  
Magnetic Colloids ◽  
Magnetic Convection

Experiments were performed to examine the influence of homogeneous magnetic field on convection instability and flows in a layer of magnetic fluid heated from one wide side and cooled from another. The temperature sensors were used for measurement of heat transport across the layer. Visualization of flow patterns was provided by a liquid crystal sheet. The results indicate that with the help of a magnetic field it is possible to control the convection stability, intensity of the heat transfer and the form of convection motions. The interaction of gravitational and magnetic convection mechanisms for different orientations of the layer and magnetic field were studied. The essential influence of gravitational sedimentation of magnetic particles and their aggregates on convection in magnetic colloids is shown. A number of non-linear regimes of convection, including localized states and repeated long-wave transients from convection to conduction were observed.

GRAVITATIONAL AND MAGNETIC CONVECTION IN MAGNETIC FLUID

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1367-1373
Author(s):  
A. A. BOZHKO ◽  
G. F. PUTIN
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Solid Phase ◽  
Fluid Flows ◽  
Homogeneous Magnetic Field ◽  
Temperature Sensors ◽  
Cylindrical Layer ◽  
Temperature Sensitive ◽  
Concentration Gradients ◽  
The Stability

Experiments were performed to examine the influence of external homogeneous magnetic field on ferrofluid convection in thin cylindrical layer heated from one wide sidewall and cooled from another. Gravitational and magnetic mechanisms of convection as well as the influence of gravitational sedimentation of particles and their aggregates on stability and structure of fluid flows are studied. The integral and local temperature sensors were used for measurement of heat transport across the layer. Visualization of flow patterns was provided by a temperature-sensitive liquid crystal sheet. The results indicate that with the help of a magnetic field it is possible to control the stability and the form of convection motions. Besides, the concentration gradients of solid phase can have material role to convection instability and heat transfer.

Analysis of magneto rheological elastomers for energy harvesting systems

2020 ◽  
Vol 64 (1-4) ◽  
pp. 439-446
Author(s):  
Gildas Diguet ◽  
Gael Sebald ◽  
Masami Nakano ◽  
Mickaël Lallart ◽  
Jean-Yves Cavaillé
Keyword(s):  
Magnetic Field ◽  
Energy Harvesting ◽  
Shear Strain ◽  
Magnetic Induction ◽  
Magnetic Particles ◽  
Homogeneous Magnetic Field ◽  
Electrical Signal ◽  
Harvesting Systems ◽  
Dc Bias ◽  
Magneto Rheological

Magneto Rheological Elastomers (MREs) are composite materials based on an elastomer filled by magnetic particles. Anisotropic MRE can be easily manufactured by curing the material under homogeneous magnetic field which creates column of particles. The magnetic and elastic properties are actually coupled making these MREs suitable for energy conversion. From these remarkable properties, an energy harvesting device is considered through the application of a DC bias magnetic induction on two MREs as a metal piece is applying an AC shear strain on them. Such strain therefore changes the permeabilities of the elastomers, hence generating an AC magnetic induction which can be converted into AC electrical signal with the help of a coil. The device is simulated with a Finite Element Method software to examine the effect of the MRE parameters, the DC bias magnetic induction and applied shear strain (amplitude and frequency) on the resulting electrical signal.

Investigation of Enhancement in Pool Boiling Heat Transfer of a Binary Temperature Sensitive Magnetic Fluid

2013 ◽  
Author(s):  
Giti Karimi-Moghaddam ◽  
Richard D. Gould ◽  
Subhashish Bhattacharya
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Magnetic Fluid ◽  
Boiling Heat Transfer ◽  
Magnetic Particles ◽  
Pool Boiling ◽  
Simulation Software ◽  
Temperature Sensitive ◽  
Magnetic Field Effects ◽  
Pool Boiling Heat Transfer

In this paper, the performance of pool boiling heat transfer using a binary temperature sensitive magnetic fluid in the presence of a non-uniform magnetic field is investigated numerically. By using a binary magnetic fluid, enhanced boiling heat transfer is obtained by thermomagnetic convection without deterioration of properties of the fluid. This work is aimed at gaining a qualitative understanding the magnetic field effects on boiling heat transfer enhancement of magnetic fluids. In order to accomplish this, the boiling process and the effects of position of the external magnetic field on flow pattern and heat transfer are investigated in a 2D rectangular domain using COMSOL Multiphysics simulation software. Finally, the boiling curves for a binary temperature sensitive magnetic fluid and its base fluid (without magnetic particles) are compared for various applied heat flux magnitudes.

MONITORING INTERPARTICLE DISTANCE IN MAGNETORHEOLOGICAL COMPOSITES

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4868-4874
Author(s):  
G. BOSSIS ◽  
E. COQUELLE ◽  
C. NOEL ◽  
F. GIULIERI ◽  
A. M. CHAZE
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
Energy Dissipation ◽  
Viscoelastic Properties ◽  
Magnetic Particles ◽  
Interparticle Distance ◽  
Magnetorheological Elastomer ◽  
Magnetorheological Elastomers ◽  
Magnetic Spheres ◽  
The Creation

We describe two different systems, the first one based on a magnetorheological elastomer and the second one on magnetic particles inside a liquid crystal. In both system we manage to have chain structures with particles that are not in contact. The effect of the gap between particles on the viscoelastic properties are studied. We show in particular how in magnetorheological elastomers, the energy dissipation is closely related to the creation and the motion of cavities in the gap between the particles. In liquid crystal chaining of particles can occur without applying a magnetic field. This happens if the anchoring of liquid crystal on the surface of the particles is homeotropic. We demonstrate how the combination of elastic defects and of a magnetic field allow to obtain microscopic springs made of a pair of magnetic spheres.

The investigation of simultaneous heat transfer of water/Al2O3 nanofluid in a close enclosure by applying homogeneous magnetic field

2017 ◽  
Vol 133 ◽  
pp. 674-688 ◽  
Author(s):  
Ramin Sarlak ◽  
Shahrouz Yousefzadeh ◽  
Omid Ali Akbari ◽  
Davood Toghraie ◽  
Sajad Sarlak ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Homogeneous Magnetic Field ◽  
Simultaneous Heat ◽  
Al2o3 Nanofluid

scholarly journals Symmetry and Asymmetry in the Thermo-Magnetic Convection of Silver Nanofluid

Symmetry ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1891
Author(s):  
Elzbieta Fornalik-Wajs ◽  
Aleksandra Roszko ◽  
Janusz Donizak
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Flow Structure ◽  
Magnetic Induction ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Two Phase ◽  
Cubical Enclosure ◽  
Magnetic Convection ◽  
Rayleigh Benard

Application of nanofluids is aimed at enhancing the heat transfer performance the same as the utilization of a strong magnetic field. The potential of the combined effect of these passive and active methods was analyzed numerically. The silver nanofluid thermo-magnetic convection in a cubical enclosure placed in the Rayleigh–Benard configuration was investigated for various concentrations of nanoparticles and various values of magnetic induction at constant temperature difference. The nanofluid flow was considered as a two-phase flow and studied with the Euler–Euler approach. The main outcome was related to the heat transfer performance, but also a lot of attention was paid to the flow structure, which is very difficult to obtain by experimental methods. The results exhibited a flow structure with diagonal axis of symmetry in all analyzed cases and stabilizing effect of magnetic field. The heat transfer performance is indicated by the Nusselt number, which increases with an increasing value of magnetic induction but decreases with an increasing concentration of nanoparticles.

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

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4783
Author(s):  
Rafał Bielas ◽  
Arkadiusz Józefczak
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Magnetic Particles ◽  
Surrounding Medium ◽  
Pickering Emulsions ◽  
Stable Particle ◽  
Heating And Cooling ◽  
Magnetic Heating ◽  
Potential Applications ◽  
The Magnetic Field

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.

scholarly journals Importance of Basset History Force for the Description of Magnetically Driven Motion of Magnetic Particles in Air

2020 ◽  
Vol 20 (2) ◽  
pp. 50-58 ◽  
Author(s):  
Andrej Krafcik ◽  
Peter Babinec ◽  
Melania Babincova ◽  
Ivan Frollo
Keyword(s):  
Magnetic Field ◽  
Magnetic Particles ◽  
Magnetic Force ◽  
Magnetic Particle ◽  
Homogeneous Magnetic Field ◽  
Gradient Magnetic Field ◽  
Driven Systems ◽  
Long Time ◽  
History Force ◽  
Stokes Force

AbstractLungs are used as an attractive possibility for administration of different therapeutic substances for a long time. An innovative method of such administration widely studied nowadays is the application of aerosolized magnetic particles as the carriers to the lungs in the external non-homogeneous magnetic field. For these reasons we have studied dynamics of such a system on a level of particle trajectory in air in the presence of magnetic force as a driving force exerted on micrometric magnetic particle. On two typical examples of magnetically driven systems—motion of magnetic particle in a gradient magnetic field and cyclotron-like motion of a charged particle in homogeneous magnetic field in microscale, where the external accelerating forces are very large and the relevant time scale is of the order from fraction of milliseconds to seconds, we have examined the importance of these forces. As has been shown, for particles with high initial acceleration, not only the commonly used Stokes force but also the Basset history force should be used for correct description of the motion.

scholarly journals Magnetic Assembly and Functionalization of One-Dimensional Nanominerals in Optical Field

2021 ◽  
Author(s):  
Meng Fu ◽  
Zepeng Zhang ◽  
Rui Jiang ◽  
Hongbao Liu
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
Clay Minerals ◽  
Magnetic Particles ◽  
Solid Content ◽  
Field Direction ◽  
Magnetic Field Direction ◽  
One Dimensional ◽  
Display Devices ◽  
The Magnetic Field

Magnetic particles can be oriented along the magnetic field direction to achieve orderly arrangement under the magnetic field. Optical functional materials such as photonic crystal and liquid crystal can be obtained according to magnetic induced ordered nanostructure assembly. One-dimensional natural clay minerals with unique structure, composition and properties can be used as structural base to prepare anisotropic magnetic nanoparticles by decorated with magnetic particles, achieving unique optical functional properties. In this chapter, one-dimensional clay minerals@Fe3O4 nanocomposites were prepared by co-precipitation. The resulting one-dimensional clay minerals@Fe3O4 nanocomposites are superparamagnetic. They can be oriented along the direction of the magnetic field and produce an instantaneously reversible response. These magnetic mineral materials can be dispersed in a dilute acid solution to form stable colloid solutions. These stable colloid solutions produce a similar magnetically controlled liquid crystal with Bragg diffraction under an external magnetic field. Their optical properties are affected by magnetic field intensity, magnetic field direction and solid content. The results show that the functionalization of one-dimensional clay minerals has potential applications in display devices, photonic switches and other fields.

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