Enhancement of Heat Transfer in Miniaturized Channels Using Ferrohydrodynamic Convection

2003 ◽  
Author(s):  
Ranjan Ganguly ◽  
Swarnendu Sen ◽  
Ishwar K. Puri
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
External Magnetic Field ◽  
Rectangular Channel ◽  
Colloidal Dispersion ◽  
Electronic Cooling ◽  
Fluid Temperature ◽  
Heat Transfer Augmentation ◽  
Nusselt Numbers ◽  
The Magnetic Field

Heat transfer in miniaturized channels and slots in electronic cooling applications is restricted by relatively low convection due to flow limitations. The flow is generally laminar and heat transfer in these small geometries is usually conduction limited. We have proposed the use of ferrofluids as coolants in the presence of a nonuniform external magnetic field to enhance the heat transfer. A magnetic ferrofluid consists of a stable colloidal dispersion of subdomain magnetic nanoparticles in a liquid carrier that remain suspended due to their thermal Brownian energy. Under a varying external magnetic field (B), a ferrofluid experiences a local volumetric body force (M.∇)B. The magnetization M of the ferrofluid is coupled with the fluid temperature through its density and magnetic susceptibility. In our simulations, a strong magnetic field is considered to be applied by placing an edge pole adjacent to one of the walls of a rectangular channel. The channel is assumed to carry a pressure-driven ferrofluid flow. The resulting flowfield is predicted by numerically solving the coupled mass, momentum, energy, and Maxwell’s equations. A parametric study is performed to identify the influence of the magnetic field strength on the temperature distribution and the resulting heat transfer. A comparison based on the local and average Nusselt numbers shows that there is a significant heat transfer augmentation due to the magnetic field.

Viscomagnetic Heat Flux Experiments as a Test of Gas Kinetic Theory in the Burnett Regime

1978 ◽  
Vol 33 (7) ◽  
pp. 749-760 ◽  
Author(s):  
G. E. J. Eggermont ◽  
P. W. Hermans ◽  
L. J. F. Hermans ◽  
H. F. P. Knaap ◽  
J. J. M. Beenakker
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Heat Flux ◽  
External Magnetic Field ◽  
Room Temperature ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Gas Kinetic Theory ◽  
The Magnetic Field ◽  
Good Agreement

In a rarefied polyatomic gas streaming through a rectangular channel, an external magnetic field produces a heat flux perpendicular to the flow direction. Experiments on this “viscom agnetic heat flux” have been performed for CO, N2, CH4 and HD at room temperature, with different orientations of the magnetic field. Such measurements enable one to separate the boundary layer contribution from the purely bulk contribution by means of the theory recently developed by Vestner. Very good agreement is found between the experimentally determined bulk contribution and the theoretical Burnett value for CO, N2 and CH4 , yet the behavior of HD is found to be anomalous.

A Study on Heat Transfer Suppression Characteristics of Ferrofluid with Various Magnetic Field Intensities

2019 ◽  
Vol 801 ◽  
pp. 199-204
Author(s):  
Jae Hyeong Seo ◽  
Namwon Kim ◽  
Moo Yeon Lee
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Mass Motion ◽  
Governing Equations ◽  
Cold Side ◽  
Nusselt Numbers ◽  
Insulation Performance ◽  
The Magnetic Field

The objective of this study is numerically to investigate the heat transfer suppression characteristics of the ferrofluid with the various magnetic field intensities. In order to analyze the heat transfer suppression characteristics of the ferrofluid, the temperature characteristics and average Nusselt numbers of the ferrofluid were considered with variation of the magnetic field intensity. The magnetic field intensity ranged from 0 to 30000 A/m in order to analyze the effect of the magnetic field intensity on the insulation performance of the ferrofluid. The governing equations for mass, motion, momentum, energy, magnetization and Maxwell are used for the numerical analysis of the ferrofluid. The GSMAC method was used to solve the equations. The average temperatures of the ferrofluid at left cooled area were decreased with the increase of the magnetic field intensities. The average Nusselt numbers of the ferrofluid at the hot side with the magnetic field intensities of 10000 A/m, 20000 A/m and 30000 A/m were 43.7%, 61.4% and 63.8% lower than those at the magnetic field intensity of 0 A/m, respectively. The average Nusselt numbers of the ferrofluid at the cold side with the magnetic field intensities of 10000 A/m, 20000 A/m and 30000 A/m were 50.5%, 79.7% and 83.3% lower than those at the magnetic field intensity of 0 A/m, respectively. The heat transfer characteristics of the ferrofluid were suppressed under strong magnetic field intensity. As a result, the ferrofluid could be considered to improve the insulation performance of thermal storage tank.

scholarly journals Effect of Magnetic Field on the Forced Convective Heat Transfer of Water–Ethylene Glycol-Based Fe3O4 and Fe3O4–MWCNT Nanofluids

2021 ◽  
Vol 11 (10) ◽  
pp. 4683
Author(s):  
Areum Lee ◽  
Chinnasamy Veerakumar ◽  
Honghyun Cho
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Field Strength ◽  
Ethylene Glycol ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Hybrid Nanofluid ◽  
Forced Convective Heat Transfer ◽  
The Magnetic Field

This paper discusses the forced convective heat transfer characteristics of water–ethylene glycol (EG)-based Fe3O4 nanofluid and Fe3O4–MWCNT hybrid nanofluid under the effect of a magnetic field. The results indicated that the convective heat transfer coefficient of magnetic nanofluids increased with an increase in the strength of the magnetic field. When the magnetic field strength was varied from 0 to 750 G, the maximum convective heat transfer coefficients were observed for the 0.2 wt% Fe3O4 and 0.1 wt% Fe3O4–MWNCT nanofluids, and the improvements were approximately 2.78% and 3.23%, respectively. The average pressure drops for 0.2 wt% Fe3O4 and 0.2 wt% Fe3O4–MWNCT nanofluids increased by about 4.73% and 5.23%, respectively. Owing to the extensive aggregation of nanoparticles by the external magnetic field, the heat transfer coefficient of the 0.1 wt% Fe3O4–MWNCT hybrid nanofluid was 5% higher than that of the 0.2 wt% Fe3O4 nanofluid. Therefore, the convective heat transfer can be enhanced by the dispersion stability of the nanoparticles and optimization of the magnetic field strength.

Effects of uniform or non-uniform heating at bottom wall on MHD mixed convection in a porous cavity saturated by nanofluid

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Subramanian Muthukumar ◽  
Selvaraj Sureshkumar ◽  
Arthanari Malleswaran ◽  
Murugan Muthtamilselvan ◽  
Eswari Prem
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Transfer Rate ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Darcy Number ◽  
Bottom Wall ◽  
Uniform Heating ◽  
The Magnetic Field

Abstract A numerical investigation on the effects of uniform and non-uniform heating of bottom wall on mixed convective heat transfer in a square porous chamber filled with nanofluid in the appearance of magnetic field is carried out. Uniform or sinusoidal heat source is fixed at the bottom wall. The top wall moves in either positive or negative direction with a constant cold temperature. The vertical sidewalls are thermally insulated. The finite volume approach based on SIMPLE algorithm is followed for solving the governing equations. The different parameters connected with this study are Richardson number (0.01 ≤ Ri ≤ 100), Darcy number (10−4 ≤ Da ≤ 10−1), Hartmann number (0 ≤ Ha ≤ 70), and the solid volume fraction (0.00 ≤ χ ≤ 0.06). The results are presented graphically in the form of isotherms, streamlines, mid-plane velocities, and Nusselt numbers for the various combinations of the considered parameters. It is observed that the overall heat transfer rate is low at Ri = 100 in the positive direction of lid movement, whereas it is low at Ri = 1 in the negative direction. The average Nusselt number is lowered on growing Hartmann number for all considered moving directions of top wall with non-uniform heating. The low permeability, Da = 10−4 keeps the flow pattern same dominating the magnetic field, whereas magnetic field strongly affects the flow pattern dominating the high Darcy number Da = 10−1. The heat transfer rate increases on enhancing the solid volume fraction regardless of the magnetic field.

The Effect of Magnetic Field on the Hydration of Nanoscopic Hydrophobic N-Alkane Plates

2011 ◽  
Vol 228-229 ◽  
pp. 1007-1011
Author(s):  
Wei Wei Zhang ◽  
Long Qiu Li ◽  
Guang Yu Zhang ◽  
Hui Juan Dong
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Dynamics Simulation ◽  
Free Energy Barrier ◽  
Confined Water ◽  
Magnetic Exposure ◽  
Hydrophobic Solutes ◽  
The Magnetic Field ◽  
Density Of Water ◽  
Induced Adsorption

The effect of an external magnetic field on the hydration behavior of nanoscopic n-octane plates has been extensively investigated using molecular dynamics simulation in an isothermal-isobaric ensemble. The solute plates with different intermolecular spacing have also been considered to examine the effect of the topology of hydrophobic plates on the adsorption behavior of confined water in the presence of an external magnetic field with an intensity ranging from 0.1T to 1 T. The results demonstrate that magnetic exposure decreases the density of water for the plates with intermolecular spacing of a0 = 4 and 5 Å. This suggests that the free energy barrier for evaporation can be lowered by the applied field, and the hydrophobic solutes consisting of condensed n-octane molecules are apt to aggregate in the aqueous solution. In contrast, the magnetic field improves the dissolution or wetting of solutes comprised of loosely packed n-octane plates of a0=7Å. A magnetic-field-induced adsorption-to-desorption translation, which is in agreement with the experimental results provided by Ozeki, has also been observed for the plates with intermolecular spacing of a0 = 6 Å.

scholarly journals Carbon-coated Fe3O4 core–shell super-paramagnetic nanoparticle-based ferrofluid for heat transfer applications

2021 ◽  
Author(s):  
Mohd Imran ◽  
Nasser Zouli ◽  
Tansir Ahamad ◽  
Saad M. Alshehri ◽  
Mohammed Rehaan Chandan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
External Magnetic Field ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Carbon Coated ◽  
Core Shell Nanoparticles ◽  
Fe3o4 Core

Ferrofluids prepared by dispersing superparamagnetic Fe3O4@C core–shell nanoparticles in water exhibited exceptional enhancement in thermal conductivity without an external magnetic field.

Influence of Radial Rotation on Heat Transfer in a Rectangular Channel With Two Opposite Walls Roughened by Hemispherical Protrusions at High Rotation Numbers

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Shyy Woei Chang ◽  
Tong-Miin. Liou ◽  
Wei-Chun Chen
Keyword(s):  
Heat Transfer ◽  
Infrared Thermography ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Flow Region ◽  
Transfer Data ◽  
Nusselt Numbers ◽  
Rotation Numbers ◽  
Heat Transfer Correlations ◽  
Rotating Channel

Detailed heat transfer distributions over two opposite leading and trailing walls roughened by hemispherical protrusions were measured from a rotating rectangular channel at rotation number up to 0.6 to examine the effects of Reynolds (Re), rotation (Ro), and buoyancy (Bu) numbers on local and area-averaged Nusselt numbers (Nu and Nu¯) using the infrared thermography. A set of selected heat transfer data illustrates the Coriolis and rotating buoyancy effects on the detailed Nu distributions and the area-averaged heat transfer performances of the rotating channel. The Nu¯ for the developed flow region on the leading and trailing walls are parametrically analyzed to devise the empirical heat transfer correlations that permit the evaluation of the interdependent and individual Re, Ro, and Bu effect on Nu¯.

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