Magnetic Field Source Research Articles

Numerical investigation of heat source induced thermal slip effect on trihybrid nanofluid flow over a stretching surface

The fluid flow model is evaluated with the mass and energy transfer through the trihybrid nanofluid (Thnf) past a stretching permeable sheet. The proficiency of the nanofluid could be more effective, improved and stable by introducing nanoparticles with various thermal and rheological properties. The trihybrid nanoliquid has been prepared by the dispersion of silver (Ag), cobalt ferrite (CoFe2O4), and magnesium oxide (MgO) nanocomposites in water. The consequences of Darcy-Forchheimer are engaged in the momentum equation, to evaluate the permeability effect. The fluid flow is expressed in the form system of PDEs with effect of natural convection, magnetic field and heat source. Which are converted into a non-dimensional set of ODE by using similarity variables substitutions. Moreover, the numerical approach PCM (parametric continuation method) is used to deal the derived set of ODEs. The results are relatively compared to the existing study for accuracy purposes. It has been noted that the Thnf has higher thermal conductivity than ordinary and hybrid nanoliquid. The velocity field rises with the mounting values of the thermal Grashof number. The velocity curve drops with the effect of a power law, Forchheimer's, and porosity parameters.

Asymmetric magnetic levitation for density-based measurement and analysis

BackgroundMagnetic levitation (MagLev) based on negative magnetophoresis represents a promising technology for density-based analysis and manipulation of nonmagnetic objects. This approach has garnered considerable interest across multiple fields, such as chemistry, materials science, and biochemistry, primarily due to its inherent simplicity, precision, and cost-effectiveness. However, it is essential to recognize that frequently used MagLev configurations, including standard MagLev and axial MagLev, are not without their limitations. These configurations often struggle to strike a balance between levitation performance, ease of operation, and visibility. Therefore, it is necessary to develop a new MagLev configuration to address the aforementioned issue. ResultsThis work describes the development of an innovative MagLev, termed “asymmetric MagLev”, achieved by combining a ring magnet and a cylinder magnet as up-down asymmetric magnetic field sources. The asymmetric design overcomes the physical obstacles along the centerline of the standard MagLev, offering unique open-structure advantages, including easy handling of samples, the ability to observe samples from the top or bottom, and no restrictions on the container height. Meanwhile, comparative analysis reveals a considerable enhancement in the working distance of the asymmetric MagLev without significantly sacrificing the measurement range compared to the axial MagLev. Notably, the asymmetric MagLev achieves a remarkable sensitivity of up to about 1.8 × 104 mm (g cm−3)−1, surpassing the axial MagLev by approximately 30 times. Furthermore, experimental results validate the successful application of the asymmetric MagLev in density measurement and quality detection of small-sized objects. SignificanceThis pioneering configuration represents the first utilization of up-down asymmetric magnets in the field of MagLev. Through the integration of an axially magnetized ring magnet and a cylinder magnet, the asymmetric MagLev design overcomes the limitations associated with conventional MagLev configurations. This innovative design exhibits outstanding operational capabilities and levitation performance, making it suitable for a wide range of applications in density-based measurement and analysis.

Surface Functionalization, Nucleic Acid Tether Characterization, and Force Calibration for a Magnetic Tweezers Assay.

Magnetic tweezers are a force spectroscopy single-molecule technique. They enable the mechanical manipulation of biomolecules via the means of a magnetic particle under an attractive force applied by a magnetic field source. The magnetic particle is tethered to the glass surface of a flow chamber by the biomolecule, and functionalization strategies have been developed to reduce the nonspecific interactions of either the magnetic particles or biomolecules with the surface. Here, we describe two complementary strategies to achieve a high tether density while reducing the interactions of both the magnetic particle and the biomolecule of interest with the glass surface. Using a large detector CMOS camera, the simultaneous observation of several hundreds of tethered magnetic beads is achievable, allowing high-throughput single-molecule measurements. We further describe here a simple procedure to perform the calibration in force of a magnetic tweezers assay.

The effect of blanket system and port plugs on the harmonic components of error field and optimizing approach investigation

The fusion plasma is sensitive to the penetration of the toroidal mode numbers harmonic components of the error fields (EFs), and the toroidal mode components of the EFs are closely tied to the toroidal distribution of the magnetic field source. The primary source of EFs within the magnetic field sources is the current source, such as the magnet system, while the magnetic field produced by magnetized ferromagnetic materials may also generate EFs. The ferromagnetic field source, such the reduced-activation ferritic-martensitic steel, represent a smaller portion of the EFs source. However, the use of ferromagnetic materials is expected to increase significantly as tokamak research transitions from experimental devices to demonstration and commercial reactors, particularly for the structural materials of in-vessel components and port plugs. Predictably, the EFs induced by ferromagnetic materials will increase and may even surpass the design specifications. In this study, the EFs introduced by the water-cooling ceramic breeder blanket system and the vacuum vessel port plugs of China Fusion Engineering Test Reactor are comprehensively analyzed by an analytical approach and finite element numerical approach, which is based on the Fourier decomposition. The results reveal a clear linear relationship between the EFs formed by the saturated magnetization module and its rigid displacement deviating from periodic symmetry, as well as the same behavior in EFs and overall magnetization intensity. Compared to the assembly error of the blanket system, the EFs that may be introduced by the equatorial ports and plugs are substantial, including larger toroidal mode harmonic components that can lead to lock mode and disruption. Moreover, using the correlation between harmonic components and symmetrical periods, specific toroidal mode components can be selectively shielded.

MAGNETIC FIELD CONTROL IN AN ANALYTIC PLATFORM FOR ASSESSMENT OF PATHOGENIC BACTERIA

The paper presents a conceptual, analytical platform with various pathogen detection applications, based on a hybrid magnetic field source, comprised of permanent magnets and solenoid coils fixed on the same magnetic yoke that acts as a magnetic flux concentrator. The magnetic field creates magnetization forces that guide functionalized paramagnetic microparticles through the volume of an analyte sample, in order to capture targeted pathogens. The presence of bacteria is sensed with an additional electrical impedance spectroscopy (EIS) module attached to the system, at high-frequency electrical fields. The magnetic field control is studied using mathematical modeling and numerical simulation in several geometry setups, coil excitation, and remanent flux density values.

Damping of an Oscillatory System with Incomplete Sealing of the Air Cavity by a Magnetic Fluid

Purpose. Investigate the damping of an oscillatory system with incomplete sealing of the air cavity with a magnetic fluid.Methods. The study was carried out on an experimental setup developed on the basis of known methods and equipment for magnetic measurements and manufactured independently. A ring neodymium magnet (NdFeB alloy) 60x24x10 mm in size was used as a magnetic field source. The magnetic field strength at the center of the magnet, measured with a TPU-01 milliteslamer, is 220 kA/m. An inductor, a GVT-427B amplifier, and a GwInstek GDS-72072 digital oscilloscope were used to display oscillograms. Samples of magnetic fluid based on Fe3O4 magnetite stabilized with oleic acid were studied. Kerosene was used as the carrier liquid.Results. The results of an experimental study of the elasticity and damping of an oscillatory system with incomplete sealing of the air cavity by a magnetic fluid bridge are presented. The level of sealing of the air cavity varies due to the process of pumping gas through capillaries of various radii. To explain the regularities obtained, a model theory is proposed in the approximation of a viscous gas flow according to the Poiseuille law, and the conclusions of the wellknown theory of sound propagation in molecular acoustics and the theory of sound ducts are also drawn. The relaxation mechanism imposes a restriction on the type of vibrational gas flow through the capillaries, which takes into account the "throughput" capacity of the capillaries. The proposed model explains the presence of a maximum in the dependence of the attenuation coefficient on the capillary radius and its decrease with an increase in the volume (height) of the gas cavity.Conclusion. The proposed relaxation theory of vibrational gas flow through capillaries predicts anomalously large damping coefficients and almost complete damping of an oscillatory system with a magnetic fluid inertial element. The use of the data obtained is advisable in the design of new shock absorbers, since a magnetic fluid damper with capillaries is capable of damping low-frequency oscillations.

Thermo-solutal transportation in Reiner Philippoff liquid under influence of non-Fourier’s law on hybrid nanofluid model

Current investigation aims for determining the comparative performance of heat transfer and mass diffusion between HMC (Hamilton Crosser)-model and YMO (Yamada Ota)-model in Reiner Philippoff liquid with a magnetic field and heat source towards a vertical plate. Transportation of mass species and temperature carried out by non-Fourier’s law and solar thermal radiation involving chemical reaction and heat sink. HMC-model and YMO model are prepared using hybrid nano-strictures. In comparing points of view, the complex behavior of such hybrid nanofluids utilizing different approaches Ise obtained, such as thermal conductivity, heat transfer, and viscosity. It was investigated that HMC and YMO-hybrid nanofluid models are addressed for obtaining maximum thermal enhancement which is applicable in electronic devices, solar systems, cooling processes, aircraft engines, thermal therapy, etc. The key reason for choosing of HMC-model and YMO-model is based on correlations associated with thermal conductivity improvement in hybrid nanofluids. A non-uniform magnetic force has been placed at the surface of the wall using ethylene glycol. A system related to ODEs is achieved using the concept of similarity variables and the developing flow model is numerically simulated by the finite element method. The analysis reveals that the performance of thermal energy and flow behavior for the case of Yamada Ota hybrid-nanofluid model is higher than the performance of thermal energy and flow behavior for the case of Hamilton Crosser hybrid-nanofluid model. The temperature field increases with large values of time relaxation number, heat source number (Ht), and very small ϵ1. Magnetic parameters have a significant impact on the velocity field. Further, BL (boundary layer)-thickness associated with mass diffusion is addressed as decreasing function Sc,ϵ2, and Kc and increasing function of λ2. The temperature curve enhances with increasing values of solar thermal radiation number (Qs) and magnetic parameter M.

Numerical analysis of particulate Reiner–Rivlin flow in an asymmetric convergent channel with a heat source and magnetic field

ABSTRACT The goal of the current investigation is to examine the impact of magnetic field and heat source effects on a Reiner–Rivlin particulate flow through an asymmetric channel (convergent channel). The transformed governing equations are solved by employing the shooting technique with the RK4 method. To check the convergence of the computational results, a grid independence test has been performed. The impact of influential parameters on fluid as well as particle phases of velocity and temperature fields have been analyzed graphically. The present results exactly match previously published results in some limited cases. As the Reynolds number and magnetic parameter increase, the fluid phase velocity increases on the left side and decreases on the right part of the channel. Different fields, including metal steam resistors, paper production, and fibre suspension, are significantly impacted by the magnetic field’s effect on Reiner–Rivlin fluid through asymmetric channels.

Stimulation of peroneal nerves reveals maintained somatosensory representation in transtibial amputees.

Several studies have found changes in the organization of the primary somatosensory cortex (SI) after amputation. This SI reorganization was mainly investigated by stimulating neighboring areas to amputation. Unexpectedly, the somatosensory representation of the deafferented limb has rarely been directly tested. We stimulated the truncated peroneal nerve in 24 unilateral transtibial amputees and 15 healthy controls. The stimulation intensity was adjusted to make the elicited percept comparable between both stimulation sides. Neural sources of the somatosensory-evoked magnetic fields (SEFs) to peroneal stimulation were localized in the contralateral foot/leg areas of SI in 19 patients and 14 healthy controls. We demonstrated the activation of functionally preserved cortical representations of amputated lower limbs. None of the patients reported evoked phantom limb pain (PLP) during stimulation. Stimulation that evoked perceptions in the foot required stronger intensities on the amputated side than on the intact side. In addition to this, stronger stimulation intensities were required for amputees than for healthy controls. Exploratorily, PLP intensity was neither associated with stimulation intensity nor dipole strength nor with differences in Euclidean distances (between SEF sources of the healthy peroneus and mirrored SEF sources of the truncated peroneus). Our results provide hope that the truncated nerve may be used to establish both motor control and somatosensory feedback via the nerve trunk when a permanently functional connection between the nerve trunk and the prosthesis becomes available.

Heat transfer analysis of magnetized Cu-Ag-H2O hybrid nanofluid radiative flow over a spinning disk when the exponential heat source and Hall current are substantial: Optimization and sensitivity analysis

The main motive of the instigated mathematical model is to observe the impact of Hall current on the hybrid nanofluid flow over a disk that is rotating. The copper and silver metal nanoparticles have been considered with volume fraction φ1=φ2=0.01(0.01)0.04 and are suspended in water to form the hybrid nanofluid. Diverse characteristics like magnetic field, thermal radiation, and (ESHS) exponential space dependent heat source are incorporated to investigate the nature of the flow. The present mathematical model is initiated with partial derivative equations (PDEs) which are redrafted as ordinary derivative equations (ODEs) with appropriate transformations of similarity. The results are attained through a blend of the Runge-Kutta method, shooting procedure, and the influences of parameters on the flow of nanofluid and hybrid nanofluid are compared and illustrated both as tables and graphs. The present numerical research is unique because by employing a complete quadratic CCD framework using the RSM strategy, the sensitivity and optimization analysis of the heat transmission improvement for the volume fraction, ESHS, and thermal radiation parameters have been performed. The R-squared and adjusted R-Squared are obtained as 100%. The residual graphs and contour diagrams of the same are also shown. The current study establishes that the Hall parameter increases the radial velocity, but it also controls the energy and cross-radial velocity. The rate of heat transmission is increased by thermal radiation even at low levels of ESHS. The rate of heat transmission is more sensitive (0.024670) to the volume fraction of the hybrid nanofluid when ESHS is at an intermediate level. The lowest sensitivity (-1.269967) value towards ESHS is observed For thermal radiation and ESHS parameter values, the heat transmission rate of the mono nanofluid is not as great as that of hybrid nanofluid. The current study finds applications in the generation of hydroelectric power, air cleansing and rotating equipment, healthcare devices, and many other industries.

3D Hybrid Segmented Layer Modeling of On-Load Magnetic Fields and Torques for Coreless Axial-Flux Permanent Magnet Synchronous Motor

This paper presents a novel 3-dimensional hybrid segmented layer model (3D HSLM) for coreless axial-flux permanent magnet synchronous motors (AFPMSMs). In the proposed 3D HSLM, the magnetic field sources are divided into the PM array and current-driven electro-magnets, which are captured by the combination of the magnetic scalar potential and vector potential models. This paper proposes a geometry function and cylindrical harmonic index modulation functions in order to correctly capture the curvature effect by the PMs and coils with arbitrary shapes and also the radial edge effect from the finite lengths of the rotor and the stator. The proposed modeling method also enables accurate estimation of the motor characteristics on the on-load conditions using the magnetic vector potential model. The fidelity of the proposed 3D HSLM is validated against the equivalent FEM models for various cases with different PM and coil shapes, in terms of the airgap magnetic fields, motor torque, and flux linkage. The comparison results show that the proposed 3D HSLM yields a modeling accuracy of more than 98% while significantly reducing the calculation time by two orders of magnitude as compared to the FEM models.

Hydrothermal bioconvective Bödewadt ternary composition nanofluids flow over a stretching rotating disk through a heat generating porous medium

The bioconvective Bödewadt flow of ternary composition nanofluids over a three-dimensional stretched rotating disk is explored. The considered stream layer is filled by a porous medium and the inertia impacts are not neglected. Several physical issues are analyzed such as second order slip, strong magnetic field, thermal radiation, and temperature-dependent heat source. Also, exponential features are assumed for the heat source and Arrhenius activation energy. The components of the ternary nanofluids are spherical Al2O3 nanoparticles, MWCNT cylindrical nanoparticles and platelet graphene nanoparticles and suitable correlations for the thermophysical properties are introduced. The irreversibility properties in all the aforementioned cases are analyzed. The solution methodology depends on transforming the governing system to similar forms then they are solved using 4th order Rung-Kutta method. The obtained results disclosed that the temperature features are higher in case of ternary nanofluids compared to the hybrid and mono nanofluids cases. Also, the given outcomes recommend using the mono nanofluids to obtain lower system irreversibility.

Computational investigation of double non-uniform magnetic field on heat transfer of nanofluid stream along 180-degree elbow pipe

The thermal efficiency of the nanofluid flow along the 180-elbow pipe is investigated under effects of double source of non-uniform magnetic field. To model the nanofluid stream with double magnetic sources, computational fluid dynamic is used. Effects of magnetic intensities and velocity of nanofluid on the hydrodynamic of the chosen model is also investigated in this research. The results of simulation indicate that the vortices are generated near the magnetic field and these vortices extend the thermal layer into the main stream and consequently, thermal efficiency of nanofluid stream is enhanced in 180-degree elbow. The results of various magnetic intensities also show that the increasing the magnetic intensities changes the location of maximum heat transfer from 1st magnetic source to 2nd one.

Simulation of the magnetic field in residential buildings with built-in substations based on a two-phase multi-dipole model of a three-phase current conductor

Problem. Substations 10(6)/0.4 kV built into residential buildings create a magnetic field with magnetic flux density of more than 10 μT in nearby residential premises, which is a danger to the health of the population and makes the study of this magnetic field relevant for the development of methods for its protection. The main source of the substations external magnetic field is their low-voltage current conductor, the contribution of which to the total level of the magnetic field is more than 90 %. Multi-dipole mathematical models, which have a clear physical interpretation, are a promising method of modeling the substations magnetic field, which is important for the further development of methods of population protection. The purpose of the work is to modify the well-known multi-dipole model for calculation based on it with a limited error of the external magnetic field of current conductors of built-in substations that are close to residential buildings at a distance of up to one meter. Methodology. A modified two-phase multi-dipole mathematical model of the main source of the external magnetic field of substation – its three-phase low-voltage current conductors – is proposed, which, unlike the existing model, is based on a two- you to halve the distance to the area of calculation without increasing the error. Verification. An experimental verification of the modified two-phase multi-dipole model of the magnetic field of a three-phase 100 kVA transformer substation on its full-scale physical model was carried out, and the results of the experiment were presented, confirming the coincidence of the calculation and the experiment with a spread of no more than 7 %.

Design and comparison of electro-permanent magnetic field sources for magnetocaloric heat pumps

We present the results of a comprehensive study of the design, numerical analyses and experimental validation of various electro-permanent magnetic structures that can be used in magnetocaloric refrigeration. Most magnetic field sources currently used in conceptual magnetic cooling devices require moving parts, which produce noise, vibrations and require maintenance. Furthermore, the operating frequency of such magnetic structures is relatively low and limited by aspects of the mechanical construction. Unlike any magnetic structure currently used in a magnetocaloric refrigeration device, the presented structure consists of a hybrid assembly of an electromagnet and a permanent magnet. We report on how different configurations of permanent magnets and the windings of electromagnets, including the air gaps, affect the energy efficiency, the input power and the total mass of the magnetic field source. Some guidelines for future research and the development of electro-permanent magnetic field sources for magnetocaloric refrigeration and heat pumps are presented, supported by information on how such structures can enable higher operating frequencies that could increase the compactness of future magnetocaloric devices.

Heat and Mass Transfer of CNTs Blood-based Casson Nanoliquids MHD Flow over a Rotating Stretchable Disk with Magnetic Field and Heat Source

Carbon nanotubes (CNTs) are being used in nanomedicine as drug delivery systems, particularly for the medical therapy of cancer. The CNTs are initially infused into the blood, which then travels to the tumour via waves generated by the artery walls in the presence of an outside influence, like a magnetic field. This article analyses the study of heat and mass transmission in a blood-based Casson nanoliquid MHD flow using single-wall (SW) and multi-wall (MW) carbon nanotubes (CNTs) on a rotating disc with a heat source and magnetic field effects. The suspension of both kinds of carbon nanotubes is accomplished using Casson blood. The spinning and extending of the disc cause the flow to be formed. The controlling nonlinear PDEs are transformed into nonlinear ODEs, and ODEs are resolved using the Runge-Kutta fourth-order approach in MATLAB's bvp4c package. By means of graphical representation, the effects of different model restrictions are highlighted for the following parameters: momentum, energy transport, concentration, microorganism profiles, drag coefficient, heat and mass transport rates, and motile density number. This study demonstrates that the fluid momentum of a single-walled CNTs-blood Casson nanofluid is relatively less impacted and that the heat profile of this nanofluid is more dominant than that of a multi-walled CNTs-blood nanoliquid. The outcomes further show that with higher levels of the volume fraction of nanoparticles, the friction factor and rate of heat transport are improved.

A Suitable Magnetic Field Source Composed of an HTS Coil and HTS Bulks for Magnetic Drug Delivery System

To realize Magnetic Drug Delivery System (MDDS), it is necessary to reduce the frictional force on the inner surface of the blood vessel and increase the magnetic force in the longitudinal direction of the blood vessel acting on magnetic drugs deep inside the body. In other words, where the magnetic drugs are concentrated, the magnetic flux density gradient in the longitudinal direction of the blood vessel must be large and the magnetic flux density gradient perpendicular to the blood vessel surface must be small. However, creating such a magnetic field distribution with a single magnetic field source is difficult. Therefore, we investigated a magnetic field source configuration method that can increase the magnetic flux density gradient in the longitudinal direction of the blood vessel and decrease the magnetic flux density gradient perpendicular to the blood vessel surface by configuring the magnetic field source with an HTS coil and zero-field-cooled HTS bulks and using the antimagnetic effect of the HTS bulks. We examined the effect of the number of cylindrical HTS bulks on the magnetic force acting on the magnetic drugs. The shielding current field of the HTS bulk had the effect of reducing the magnetic flux density gradient perpendicular to the blood vessel surface and the relative position of the area where the magnetic drugs are concentrated and the shielding current region within the HTS bulk greatly affected the magnetic flux density gradient perpendicular to the blood vessel surface. Based on these results, we examined the effect of the distance between two cylindrical HTS bulks placed inside an HTS coil on the magnetic force acting on the magnetic drugs. The magnetic force in the longitudinal direction of the blood vessel was able to be increased by placing the HTS bulks so that the boundary of the HTS bulk (shielding current region) is near the area directly below the area where the magnetic drugs are concentrated. The distance between the square-column HTS bulks that maximized the magnetic force was longer than that of the cylindrical HTS bulks.

Noninvasive blood glucose sensing by secondary speckle pattern artificial intelligence analyses.

Diabetes is a prevalent disease worldwide that can cause severe health problems. Accurate blood glucose detection is crucial for diabetes management, and noninvasive methods can be more convenient and less painful than traditional finger-prick methods. We aim to report a noncontact speckle-based blood glucose measurement system that utilizes artificial intelligence (AI) data processing to improve glucose detection accuracy. The study also explores the influence of an alternating current (AC) induced magnetic field on the sensitivity and selectivity of blood glucose detection. The proposed blood glucose sensor consists of a digital camera, an AC-generated magnetic field source, a laser illuminating the subject's finger, and a computer. A magnetic field is applied to the finger, and a camera records the speckle patterns generated by the laser light reflected from the finger. The acquired video data are preprocessed for machine learning (ML) and deep neural networks (DNNs) to classify blood plasma glucose levels. The standard finger-prick method is used as a reference for blood glucose level classification. The study found that the noncontact speckle-based blood glucose measurement system with AI data processing allows for the detection of blood plasma glucose levels with high accuracy. The ML approach gives better results than the tested DNNs as the proposed data preprocessing is highly selective and efficient. The proposed noncontact blood glucose sensing mechanism utilizing AI data processing and a magnetic field can potentially improve glucose detection accuracy, making it more convenient and less painful for patients. The system also allows for inexpensive blood glucose sensing mechanisms and fast blood glucose screening. The results suggest that noninvasive methods can improve blood glucose detection accuracy, which can have significant implications for diabetes management. Investigations involving representative sampling data, including subjects of different ages, gender, race, and health status, could allow for further improvement.

Laser powder bed fusion of anisotropic Nd-Fe-B bonded magnets utilizing an in-situ mechanical alignment approach

Nd-Fe-B bonded magnets are an important class of permanent magnets, employed in many technological sectors. Additive Manufacturing (AM) enables the fabrication of net-shape bonded magnets with complex geometries, allowing to tailor their magnetic stray field specifically for a given application. A crucial challenge is the production of magnetically anisotropic components. Approaches presented in the literature up to now required a post-printing procedure or the complex integration of a magnetic field source into the AM process. Here, we present a technique to fabricate anisotropic bonded magnets via Laser Powder Bed Fusion (LPBF) by utilizing the mechanical alignment of anisotropic particles in a single step, without the need for a magnetic field source. Anisotropic bonded magnets were fabricated using a mixture of anisotropic Nd-Fe-B powder (MQA-38–14) and polyamide-12 (PA12). This magnetic powder consists of ellipsoidal particles, where the easy magnetization axis is distributed perpendicular to their longest side, and the mean aspect ratio of 3:1 can be exploited to generate magnetic texture. Depending on the particle size used as feedstock, the degree of alignment (<cosθ>) can be tailored to a maximum of <cosθ> = 0.78. The fabricated anisotropic bonded magnets exhibited a maximum remanence of Jr = 377 mT and an energy product of (BH)max = 28.6 kJ/m3, respectively.

Shape and Stability of a Local Heat-Transfer Magnetofluid Coating on a Plate

Purpose. Investigate the shape and stability of a magnetic fluid coating on a flat surface in a non-uniform magnetic field of a permanent magnet.Methods. Magnetic fluids based on transformer oil MMT-44 and MMT-21 with saturation magnetization of 43.8 and 21.2 kA/m, respectively, were used in the experiments. A magnetic-fluid coating was formed on the surface of horizontal and vertical non-magnetic plates in a locally inhomogeneous magnetic field of permanent magnets. The source of the inhomogeneous magnetic field is a system of two rectangular magnets. The size of the magnetic system is 40×12×10 mm. The maximum values of the magnetic field strength and gradient reach 180 kA/m and 8∙104 kA/m2, respectively. The shape and stability of a sessile and suspended magnetic fluid coating were studied for various plate orientations.Results. The shape and stability of the magnetic fluid coating on horizontal and vertical plates are studied. The experimental dependences of the height and length of the coating on the volume of the magnetic fluid are established. It is established that the coating can have a certain maximum volume. When this volume is exceeded, the liquid spreads over the surface of the plate or a part of the liquid volume is separated. The limiting volume of the coating is determined by the magnetic characteristics of the ferrofluid and the magnetic field.Conclusion. The possibility of forming a sessile and suspended local magnetic fluid coating on horizontal and vertical plates is established. The height and length of the magnetic fluid coating on the plate depend on the volume of the magnetic fluid, as well as on the characteristics of the magnetic system and the magnetization of the magnetic fluid. The results obtained can be used in the formation of magnetic fluid coatings of cooled sections of heated surfaces.