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.

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.

scholarly journals Stability analysis of magnetic fluids in the presence of an oblique field and mass and heat transfer

2020 ◽  
Vol 330 ◽  
pp. 01035
Author(s):  
Rabah Djeghiour ◽  
Bachir Meziani
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Magnetic Fluids ◽  
Physical Parameters ◽  
Stability Diagrams ◽  
Stability And Instability ◽  
Mass And Heat Transfer ◽  
Model Equations ◽  
The Stability ◽  
Oblique Magnetic Field

In this paper, we investigate an analysis of the stability of a basic flow of streaming magnetic fluids in the presence of an oblique magnetic field is made. We have use the linear analysis of modified Kelvin-Helmholtz instability by the addition of the influence of mass transfer and heat across the interface. Problems equations model is presented where nonlinear terms are neglected in model equations as well as the boundary conditions. In the case of a oblique magnetic field, the dispersion relation is obtained and discussed both analytically and numerically and the stability diagrams are also obtained. It is found that the effect of the field depends strongly on the choice of some physical parameters of the system. Regions of stability and instability are identified. It is found that the mass and heat transfer parameter has a destabilizing influence regardless of the mechanism of the field.

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.

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

Modeling of Thermomagnetic Phenomena in Active Magnetocaloric Regenerators

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Paulo V. Trevizoli ◽  
Jader R. Barbosa ◽  
Armando Tura ◽  
Daniel Arnold ◽  
Andrew Rowe
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Experimental Data ◽  
Solid Phase ◽  
Entropy Change ◽  
Porous Matrix ◽  
Cooling Capacity ◽  
Heat Transfer Fluid ◽  
Fluid Displacement ◽  
Matrix Heat Exchanger

The active magnetic regenerator (AMR) consists of a porous matrix heat exchanger whose solid phase is a magnetocaloric material (solid refrigerant) that undergoes a reversible magnetic entropy change when subjected to a changing magnetic field. The cooling capacity of the cycle is proportional to the mass of solid refrigerant, operating frequency, volumetric displacement of the heat transfer fluid and regenerator effectiveness. AMRs can be modeled via a porous media approach and a model has been developed in this work to simulate the time-dependent fluid flow and heat transfer processes in the regenerator matrix. Gadolinium (Gd) is usually adopted as a reference material for magnetic cooling at near room temperature and its magnetic temperature change and physical properties were accounted for through a combination of experimental data and the Weiss-Debye-Sommerfeld (WDS) theory. In this paper, the interaction of the applied magnetic field waveform with the heat transfer fluid displacement profile and the influence of demagnetizing effects on the AMR performance are investigated numerically. The numerical model is evaluated against experimental data for a regenerator containing spherical Gd particles.

scholarly journals Designing a structure of the magnetically active part of dipole electromagnets for the system of vertical convergence-separation of beams

2021 ◽  
Vol 2 (5 (110)) ◽  
pp. 14-22
Author(s):  
Andriy Getman
Keyword(s):  
Magnetic Field ◽  
Magnetic Induction ◽  
Homogeneous Magnetic Field ◽  
Heavy Ion ◽  
Active Part ◽  
Dipole Magnet ◽  
Assigned Value ◽  
Magnetic Parameters ◽  
The Third ◽  
The Stability

This paper reports the results of calculating the magnetic parameters for a direct dipole magnet in the system of vertical convergence-separation of particle beams of the upper and lower rings of the heavy-ion collider. An optimized variant of the yoke and superconducting winding structures has been obtained, providing for the assigned value of a homogeneous magnetic field inside the aperture at the minimized contributions of higher-order harmonics, average-integral along the length. The results from the analysis of the transverse projections of the magnetic induction obtained by 2D modeling of two variants of the design of the central cross-section of the dipole electromagnet are presented. The analysis results have established the dependence of the stability of magnetic parameters in the aperture of the electromagnet when the current in the winding changes on the volume of those yoke regions whose magnetization value is close to saturation. A 3D model of the magnetically active part has been built for two variants of the electromagnet design, and the values of the average-integral harmonics of transverse projections of magnetic induction in the aperture have been calculated. The relationship between the third average-integral harmonic of magnetic induction and the size lengths of the yoke and winding has been empirically established, making it possible to correct the heterogeneity of the transverse magnetic field in the aperture of the electromagnet. The results of optimization of the structure of the magnetically active part of the electromagnet are presented on the criteria for a minimum of the values of the average-integral coefficients of magnetic induction, carried out on the basis of correction of the initial geometric parameters of the yoke and winding. An improvement in the stability of magnetic parameters has been demonstrated, by 3 times, as well as a two-fold reduction in the contribution to the heterogeneity by the third average-integral harmonic when using a two-row arrangement of the winding turns inside the yoke in the design of the electromagnet

Diocotron instability in presence of a cold plasma

1969 ◽  
Vol 3 (2) ◽  
pp. 149-153
Author(s):  
Aldo Nocentini
Keyword(s):  
Magnetic Field ◽  
Dielectric Constant ◽  
Uniform Magnetic Field ◽  
Cold Plasma ◽  
Charged Particles ◽  
Cylindrical Layer ◽  
Low Density ◽  
Diocotron Instability ◽  
The Stability

The influence of the presence of a low density, cold plasma on the stability against electrostatic perturbations of a cylindrical layer of charged particles moving in a uniform magnetic field is considered. It is shown that the influence of the plasma is important when the thickness of the layer is small, and the effect is stabilizing or destabilizing whether the dielectric constant of the plasma is smaller or larger than 1. In particular it is shown that the plasma can cause an unstable precession of the layer.

Utilizing Disk Shaped Thermistors to Experimentally Determine the Prandtl Number Dependence Ranging From Vapors to Liquids

2009 ◽  
Author(s):  
Chris J. Kobus
Keyword(s):  
Heat Transfer ◽  
Prandtl Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Temperature Sensors ◽  
Temperature Sensitive ◽  
Heavy Oils ◽  
External Temperature ◽  
Transfer Data

The current research utilizes disk-shaped thermistors to indirectly measure the convective heat transfer coefficient in the case of natural convection. Thermistors are resistors which have a resistance that is extremely temperature sensitive, so that experiments can be run with exceptional resolution. Not only can the convective heat transfer be indirectly measured, but so can the surface temperature, without the need for external temperature sensors which can interfere with the phenomena itself. Utilizing these themistors, heat transfer data was taken utilizing a variety of fluids from gasses (Pr = 0.72) to heavy oils (Pr ∼ 1000). From the experimental data, it was shown that the classical Nusselt-Rayleigh type correlation does not accurately predict the Prandtl number dependence for this geometry, and a new dimensionless correlation is proposed.

Utilizing Disk Shaped Thermistors to Experimentally Determine the Prandtl Number Dependence Ranging From Vapors to Liquids

2006 ◽  
Author(s):  
Chris J. Kobus ◽  
Dan Wu ◽  
Laila Guessous
Keyword(s):  
Heat Transfer ◽  
Prandtl Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Temperature Sensors ◽  
Temperature Sensitive ◽  
Heavy Oils ◽  
External Temperature ◽  
Transfer Data

The current research utilizes disk-shaped thermistors to indirectly measure the convective heat transfer coefficient in the case of natural convection. Thermistors are resistors which have a resistance that is extremely temperature sensitive, so that experiments can be run with exceptional resolution. Not only can the convective heat transfer be indirectly measured, but so can the surface temperature, without the need for external temperature sensors which can interfere with the phenomena itself. Utilizing these themistors, heat transfer data was taken utilizing a variety of fluids from gasses (Pr = 0.72) to heavy oils (Pr ~ 1000). From the experimental data, it was shown that the classical Nusselt-Rayleigh type correlation does not accurately predict the Prandtl number dependence for this geometry, and a new dimensionless correlation is proposed.

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