Shaping of cylindrically symmetric magnetic fields with permanent magnets

As electrical devices become smaller, it is essential to maintain operating temperature for safety and durability. Therefore, there are efforts to improve heat transfer performance under various conditions, such as using extended surfaces and nanofluids. Among them, cooling methods using ferrofluid are drawing the attention of many researchers. This fluid can control the movement of the fluid in magnetic fields. In this study, the heat transfer performance of a fin-tube heat exchanger, using ferrofluid as a coolant, was analyzed when external magnetic fields were applied. Permanent magnets were placed outside the heat exchanger. When the magnetic fields were applied, a change in the thermal boundary layer was observed. It also formed vortexes, which affected the formation of flow patterns. The vortex causes energy exchanges in the flow field, activating thermal diffusion and improving heat transfer. A numerical analysis was used to observe the cooling performance of heat exchangers, as the strength and number of the external magnetic fields were varying. VGs (vortex generators) were also installed to create vortex fields. A convective heat transfer coefficient was calculated to determine the heat transfer rate. In addition, the comparative analysis was performed with graphical results using contours of temperature and velocity.

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Influence of Permanent Magnets Installation Approach on the Torque of а Magneto-Rheological Disk Brake

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.105.184 ◽

2021 ◽

Vol 105 ◽

pp. 184-193

Author(s):

Ilya Aleksandrovich Frolov ◽

Andrei Aleksandrovich Vorotnikov ◽

Semyon Viktorovich Bushuev ◽

Elena Alekseevna Melnichenko ◽

Yuri Viktorovich Poduraev

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Magnetic Materials ◽

Permanent Magnets ◽

Magnetorheological Fluid ◽

Simulation Modelling ◽

Disc Brake ◽

Large Area ◽

Braking Torque ◽

The Magnetic Field

Magnetorheological braking devices function due to the organization of domain structures between liquid and solid magnetic materials under the action of an electromagnetic or magnetic field. The disc is most widely used as a rotating braking element that made of a solid magnetic material due to the large area of contact with a magnetorheological fluid. Many factors affect the braking characteristics of the magnetorheological disc brake. Specifically, the value of the magnetic field and how the field is distributed across the work element is significantly affected at the braking torque. There are different ways to generate a magnetic field. In this study, the method of installation of permanent magnets into the construction, allowing to increase the braking torque of the magnetorheological disc brake is proposed. Simulation modelling showing the distribution of the magnetic field across the disk depending on the installation of permanent magnets with different pole orientations were carried out. The model takes into account the possibility of increasing the gap between solid magnetic materials of the structure, inside them which the magnetorheological fluid is placed. Comparative estimation of the distribution of the magnetic fields depending on the chosen method of installation of permanent magnets with different orientations of their poles is carried out. Further research is planned to focus on a comparative assessment of the distribution of magnetic fields depending on the selected material of the braking chamber.

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Development of a magnetic tracking system for monitoring soil movements induced by geohazards

E3S Web of Conferences ◽

10.1051/e3sconf/20199217007 ◽

2019 ◽

Vol 92 ◽

pp. 17007 ◽

Cited By ~ 2

Author(s):

Xiaoyu Chen ◽

Rolando P. Orense

Keyword(s):

Magnetic Fields ◽

Permanent Magnets ◽

Tracking System ◽

Soil Liquefaction ◽

Small Scale ◽

Interior Point Algorithm ◽

Tracking Accuracy ◽

Tracking Errors ◽

Magnetic Tracking ◽

Soil Movements

In the study of geotechnical hazards, such as soil liquefaction and landslides, the analysis of soil movements is always one of the major preoccupations. An efficient movement sensing technique requires the tracking of subsurface soil for the purpose of examining the mechanism involved. A magnetic tracking system is therefore proposed, with permanent magnets as trackers and magnetometers as receivers. When permanent magnets, deployed within the soil to serve as excitation sources, move with soil body during a geotechnical event, they generate static magnetic fields whose flux densities are related with the positions and orientations of the magnets. Magnetometers are used as receivers to detect the generated magnetic fields, which can be further used in calculating the magnets' locations and orientations based on appropriately developed algorithms. Comparison between situations where the trackers are exposed to air and embedded within soil was conducted to evaluate the influence of soil (wet and dry) on the tracking accuracy. Also, multi-objective tracking is realized by using the particle swarm optimization (PSO) technique combined with interior-point algorithm. The tracking errors are evaluated and applications of the proposed system in small-scale laboratory tests for geohazards are discussed.

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Magnetically Induced Flow Focusing of Non-Magnetic Microparticles in Ferrofluids under Inclined Magnetic Fields

Micromachines ◽

10.3390/mi10010056 ◽

2019 ◽

Vol 10 (1) ◽

pp. 56 ◽

Cited By ~ 5

Author(s):

Laan Luo ◽

Yongqing He

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Permanent Magnets ◽

Critical Reynolds Number ◽

Rotation Angle ◽

Flow Focusing ◽

Particle Focusing ◽

Inlet Flow Rate ◽

Induced Flow ◽

Angle Of Rotation

The ability to focus biological particles into a designated position of a microchannel is vital for various biological applications. This paper reports particle focusing under vertical and inclined magnetic fields. We analyzed the effect of the angle of rotation (θ) of the permanent magnets and the critical Reynolds number (Rec) on the particle focusing in depth. We found that a rotation angle of 10° is preferred; a particle loop has formed when Re < Rec and Rec of the inclined magnetic field is larger than that of the vertical magnetic field. We also conducted experiments with polystyrene particles (10.4 μm in diameter) to prove the calculations. Experimental results show that the focusing effectiveness improved with increasing applied magnetic field strength or decreasing inlet flow rate.

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An Analytical–Experimental Approach to Quantifying the Effects of Static Magnetic Fields for Cell Culture Applications

Applied Sciences ◽

10.3390/app10020531 ◽

2020 ◽

Vol 10 (2) ◽

pp. 531

Author(s):

Pablo Ferrada ◽

Sebastián Rodríguez ◽

Génesis Serrano ◽

Carol Miranda-Ostojic ◽

Alejandro Maureira ◽

...

Keyword(s):

Magnetic Fields ◽

Permanent Magnets ◽

Bubbly Flow ◽

Scenedesmus Obliquus ◽

Relative Difference ◽

Magnetic Flux Density ◽

The South ◽

Nannochloropsis Gaditana ◽

Static Magnetic Fields ◽

The North

This work aimed to study the effects of static magnetic fields (SMFs) on cell cultures. A glass flask was filled with a liquid medium, which was surrounded by permanent magnets. Air was introduced through a tube to inject bubbles. Two magnet configurations, north and south, were used as perturbation. Scenedesmus obliquus and Nannochloropsis gaditana, growing in Medium 1 and 2, were subjected to the bubbly flow and SMFs. Differences between media were mainly due to conductivity (0.09 S/m for Medium 1 and 4.3 S/m for Medium 2). Joule dissipation ( P ) increased with the magnetic flux density ( B 0 ), being 4 orders of magnitude higher in Medium 2 than in 1. Conversely, the time constant ( τ P ) depended on B 0 , being nearly constant for Medium 1 and decreasing at 449 s/T for Medium 2. Dissipation occurred with the same τ P (235 s) in Medium 1 and 2 at B 0 = 0.5 T. In Species 1, the SMF effect was inhibitory. For Species 2, a higher enzymatic activity was observed. For superoxide dismutase, the relative difference was 78% with the north and 115% with the south configuration compared to the control values. For the catalase, differences of 29% with the north and 23% with the south configuration compared to control condition were obtained.

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