Application Of Magnetic Fluid Research Articles

Numerical Investigation of the Magnetized Reactive Viscous Couple Stress Fluid Flow Down an Inclined Riga Plate with Variable Viscosity

Accurate determination of optimum flow and heat transfer condition is one of the major challenges faced in the application of magnetic fluid in the field of medicine and engineering, especially when applied as ferrofluids for targeted drug deliveries, treatment of hyperthermia, sealants in computer hard drives, lubricants in car shafts. In view of these important applications, a mathematical investigation of the flow and heat transfer behavior of reactive magnetic fluids containing nanostructures is presented based on a couple of stress constitutive models. The reactive fluid is assumed to flow through inclined magnetized solid boundaries for energy conversion. The formulation leads to nonlinear coupled equations. The dimensionless equations are numerically solved using the spectral Chebyshev assumed solution for the weighted residual technique, and the correctness of the solution is confirmed using the shooting Runge–Kutta method. The effects of various fluid parameters on velocity, temperature, skin friction, and heat transfer rates are described in tabular and graphical form, along with suitable physical explanations. Thermal analysis computations are also presented. According to the findings, an enhanced couple of stress fluid and variable viscosity parameters reduced the skin drag and heat transfer rate at the bottom wall. Furthermore, the thermal stability of the flow can be achieved with increasing values modified Hartman number while increasing couple stress parameter encourages thermal instability in the flow domain.

Influence of magnetic fluid evaporation on pressure resistance of magnetic fluid seal

Magnetic fluid seals have the advantages of zero leakage, long life, simple structure and high reliability, and have become one of the most widely used applications of magnetic fluids. In this paper, the effect of magnetic fluid evaporation on the pressure resistance of magnetic fluid seals is studied. In terms of theory, through theoretical calculation and simulation analysis, a calculation method for the pressure resistance of magnetic fluid seals is established. In terms of experiments, firstly, five groups of control groups were set up to conduct evaporation experiments under the same conditions, and magnetic fluids with different evaporation rates were obtained; Secondly, the performance of magnetic fluids with different evaporation rates was tested, and the flow curves, viscosity-temperature curves, and magnetic-viscosity curves of magnetic fluids were obtained respectively, and the effect of evaporation on the performance of magnetic fluids was analyzed; Finally, magnetic fluid sealing experiments with different evaporation rates were carried out. It is found that evaporation increases the pressure resistance of static seal to a certain extent, which is of great significance.

Experimental and theoretical investigation on magnetic fluid seal in capillary tube

The application of magnetic fluid (MF) in microfluidics such as micropump and microvalve has been a hot topic recent years. Furthermore, the researches and the applications of MF seal are relatively mature and systematic. However, the seal capacity, which significantly influences the performance of micropump and microvalve, has not been studied specifically and overly. This paper focuses on the theoretical and experimental study about the seal capacity of MF seal in capillary tube. Furthermore, the influence of the clearance between the heads of steel poles, the inner diameter of the capillary tube, and the length of MF plug is investigated numerically and experimentally. In the simulation work, the conventional calculation model of magnetic pressure is applied to the occasion under the presence of low magnetic field and the simulation of magnetic field in the capillary tube is also conducted. Subsequently, the experiments are conducted and compared with our theoretical simulation results. In order to improve the prediction of the theory, the influence of viscosity is considered and the optimized theoretical results are compared with conventional theoretical results, which revealed that the viscosity cannot be ignored in the study of MF seal in capillary tube.

TEST STAND FOR THE EXAMINATION OF MAGNETIC FLUIDS IN SHEAR AND SQUEEZE FLOW MODE

The application of magnetic fluids in machine design on an industrial scale has been a fact for over 20 years. In particular, magnetorheological fluids have been used in energy dissipation systems with controlled operating characteristics. The availability of these fluids, connected with the ease of modelling their rheological properties by magnetic fields, contributes to the search for areas of effective use for such substances. Determining the properties and characteristics of magnetic fluid behaviour is one of the key aspects of improving existing and developing new applications for this type of smart material. Some phenomena affecting the behaviour of magnetic fluids have not been fully explained, and a synthetic model to describe their behaviour has not yet been developed, so the research area of this type of substance is still an open chapter for materials science. The paper presents a description of the design of a test stand for examining the behaviour of magnetic fluids working in shear and compression (squeeze) flow modes. Test results are also shown, and attention is given to the problems encountered in developing measurement systems for determining the properties of fluids under magnetic field conditions.

Sedimentation of two non-magnetic particles in magnetic fluid

Magnetic fluid is a stable suspension of solid phase magnetic particles of diameter about 10 nm in a nonmagnetic carrier fluid like water or alcohol. Nowadays, the magnetic fluid is widely used in industry areas such as sealing, damping, lubricating, sound regulation, heat dissipation, and MHD beneficiation. Researchers have paid great attention to the behaviors of non-magnetic particles (NPs) in the magnetic field because magnetic fluid containing NPs can form different microstructures, which are easily controlled by applying a magnetic field. In order to appropriately use the properties of magnetic fluid in industry, it is necessary to study the interaction among NPs in detail. In this paper, a multi-physical numerical model is employed to investigate the sedimentation of two NPs in magnetic fluid subjected to an applied magnetic field. The magnetic fluid flow is simulated by lattice Boltzmann method, and magneto hydrodynamics is calculated with a self-correcting procedure of a Poisson equation solver, which enables the Ohm's law to satisfy its conservation law. A dipole force model is used to obtain the dipole interaction force between particles. In addition, as the permeability of the magnetic fluid is quite different from those of the NPs and magnetic fluid, correctly establishing the conjugate boundary condition of the magnetic intensity at the interface between the particles and surrounding fluid is a key because it affects the magnetic induction in the fluid-structure interaction area. A smooth transition scheme of the conjugate boundary condition for magnetic intensity at the interface between the particles and surrounding fluid is used in this work. The aim of this work is to investigate sedimentation of two NPs in magnetized magnetic fluid. By changing the ratio of magnetic permeability and the magnetic parameter, it is found that altering the ratio of magnetic permeability is more effective to change the trajectories of NPs, while changing the magnetic parameter can just give rise to a slight transform of particle trajectories. This can provide good theoretical support for the application of magnetic fluid in industry area, because the results in the present simulation can quantitatively analyze the controlling of the movement of NPs.

Artifacts in magnetic measurements of fluid samples.

Applications of magnetic fluids are ever increasing, as well as the corresponding need to be able to characterize these fluids in situ. Commercial magnetometers are accurate and well-characterized for solid and powder samples, but their use with fluid samples is more limited. Here, we describe artifacts which can occur in magnetic measurements of fluid samples and their impact. The most critical problem in the measurement of fluid samples is the dynamic nature of the sample position and size/shape. Methods to reduce these artifacts are also discussed, such as removal of air bubbles and dynamic centering.

Magnetization mechanism of nonferrous wear debris by magnetic fluid in ferrography

The application of magnetic fluid in ferrography has improved the technique for separating nonferrous wear debris by magnetic means. Brass debris was used as an example to analyze the magnetization mechanism based on ferrographic experiments and molecular analysis. The results show that the nanomagnetic particles in magnetic fluid attach to the surface of the micro nonferrous debris by the functional group of surfactant molecule so as to develop in that debris a positive susceptibility and make it responsive to the magnetic field. The magnetic action of the magnetic particles is selective as to the property of the debris surface to which it attaches, and the magnetization time depends on how readily of the attachment. Mathematical derivation based on mechanical models shown that the magnetic force exerted on the debris is strong enough for its precipitating on ferrogram.

Depression of Self-Excited Pressure Oscillations and Noise in the Pilot Stage of a Hydraulic Jet-Pipe Servo-Valve Using Magnetic Fluids

Magnetic fluid (MF) shows an increased saturation magnetization when exposed to a magnetic field. In order to improve the quality of servo-valve products by depressing and overcoming the self-excited high-frequency pressure oscillations and noise appearing in pilot stage of a hydraulic servo-valve, application of magnetic fluid in a hydraulic servo-valve is developed in this paper. Large damping can be introduced by the magnetic fluids into the servo-valve if magnetic fluids are filled into the working gaps of the hydraulic servo-valve torque motor. After the construction and working principle of a hydraulic servo-valve with magnetic fluids are introduced, the high-frequency pressure oscillation signals are tested and recorded when magnetic fluids are applied or not in the servo-valve. Experimental results are compared and analyzed by using FFT analysis method. It is shown that pressure oscillations of the servo-valve are depressed when magnetic fluids are applied.

Thermal flow of fluid with magnetic particles in the presence of magnetic field

A magnetic fluid is a stable colloidal solution composed of magnetic particles, surfactant, and a carrier fluid. Magnetic fluids have numerous applications. In this study, we used the computational fluid dynamics model to simulate the behavior of a magnetic fluid in a 2-D square under different conditions such as different positions and intensities of the magnetic source. The preliminary model was established and used in conjunction with experimental data obtained from a present study, in order to determine the influence of particle size and mass fraction on fluid behavior. Our results show that particles with a smaller size have better ability to dissipate heat, and a larger mass fraction would provide a stronger driving force which leads to the velocity and temperature profile. We anticipate that our model would be useful to develop newer applications of magnetic fluids and magnetic flow.

Research on Magnetization Mechanism of Nano-Magnetic Fluid

In this paper, we first analyzed the nano-magnetic fluid composition and properties. Then we studied the characteristics of nano-magnetic fluid magnetization and magnetization mechanism. In addition, we also studied the nano-Fe3O4 magnetic particle size and surface modification effect on the magnetic properties of magnetic fluids. Nano-magnetic fluid is a new type of liquid nano-composite functional material. It also has magnetism and mobility, and therefore it has many unique properties and a wide range of applications. Nano-magnetic fluid magnetization characteristic is one of its main properties, its performance and application of magnetic fluid play a decisive role.

The application of magnetic fluids in sealing nodes designed for operation in difficult conditions and in machines used in sea environment

The application of magnetic fluids in sealing nodes designed for operation in difficult conditions and in machines used in sea environment Presented in article MF seals are being researched for sea technology purposes due to their excellent tightness and low resistance of motion. These features are most valuable for ring propellers and ship's main propeller shaft. There are more reasons why technologists payf significant attention for various MF seals applications in their difficult operating conditions. For instance, an advanced pumping systems are designed with contactless (screw or centrifugal) fluid seal used as the first stage seal and then the MF seal as the main seal. Further parts of the article contain discuss of the properties of magnetic fluids in the construction of MF seals. Sample of the few systems of magnetic fluid seals are presented, which have been researched lately in our laboratory including sea conditions. The magnetic fluids used in our seals are colloidal suspensions of magnetic nanoparticles. Undertaken earlier various systems selection for sea-water purposes forced us to focus on double sealing systems, in which the MF seal is used as the second seal following a conventional system especially adapted to co-operation with MF systems. This solution successfully limits direct contact of the sealed liquid with the magnetic fluid, and the entire sealing construction secures absolute tightness of the system. Using this solution we also can reduce costs by elements high accuracy avoidance. Research and design activities are carried out in the AGH Laboratory of Seals and Magnetic Fluid Applications together with Deep Water Department of Technical University of Gdansk over the use of magnetic fluid seals in sea water environment. These activities are oriented on working out MF seals able to work effectively in machines in which low-pressure water flow takes place. The objects of experimental investigations are seals having two different nominal diameters: 50 mm and 220 mm and two research rigs of different construction had to be built up. Works are scheduled to be continued.

Advance in preparation and application of magnetic fluid in biomedical engineering

Magnetic fluid technology is the interdisciplinary product of physics,chemistry,and nanotechnology.Recently,magnetic fluid was applied widely in the fields of seal,damping,heat exchange,magnetic circuit, heat transmitter,biomedical engineering,etc.Especially,the application in biomedical engineering is a hot topic in interdisciplinary study and attracts much attention of researchers from many countries.This paper reviews the general preparation of magnetic fluid and its applications in the field of biomedical engineering including immunological analysis,biologic separation,enzymatic immobilization,target drug,magnetic hyperthermia of tumor,magnetic embolism of blood vessel,contrast agents of magnetic resonance ima百ng,ere.Although,some related products have been developed already abroad.they are expensive.Domestic research of magnetic fluid is still at the experimental stage.With the continuously intercrossing and interacting in interdisciplinary field,magnetic fluid will play an important role in the field ofbiomedical engineering. Key words: Magnetic fluid; Magnetic fluid hyperthermia; Magnetic resonance imaging; Super-paramagnetic il'on oxides; Nanoparticles

Dynamic response of a hydraulic servo-valve torque motor with magnetic fluids

As magnetic fluids (MF) show higher saturation magnetization and larger viscosity when exposed to a magnetic field, large damping forces or resistance will be exerted on the armature of a hydraulic servo-valve torque motor by magnetic fluids if they are filled into the working gaps of the motor. This paper focuses on the application of magnetic fluids in a hydraulic servo-valve torque motor, especially the influence of magnetic fluids on the dynamic response of the motor. After introducing the working principle of the torque motor with magnetic fluids, the dynamic mathematical models of the torque motor and magnetic fluids are presented. The torque working on the armature introduced by magnetic fluids is analyzed. In order to study the influence of magnetic fluids, dynamic response of the torque motor is simulated and tested when magnetic fluids are applied or not in the motor. Simulation and experimental results show an obvious influence of magnetic fluids on the dynamic response of the hydraulic servo-valve torque motor.

Sealing mechanism of magnetic fluids

Sealing is one of the most successful applications of magnetic fluids. However, the sealing pressure difference is not satisfactory. This paper theoretically analyzes the mechanism of magnetic fluids sealing. Main factors that have significant effects on the sealing ability include viscous stress on the interfacial surface, magnetic surface tension, and the shape of the interfacial surface. The sealing pressure with magnetic fluids decreases with increase of rotational speed. Experiments were carried out to study the stability of the interface between magnetic fluids and water. It has been shown that stability of the interface will be damaged by washing of water when the relative flow between water and magnetic fluid becomes turbulent.

磁性流体の医療分野への応用

磁性流体の医療分野への応用

Investigating magnetic fluids by means of complex susceptibility measurements

There is an ever-increasing interest in the study and application of magnetic fluids and thus it is important to be able to accurately characterise such fluids. One method is by the measurement of the frequency dependent, complex susceptibility, χ( ω)= χ′( ω)−i χ″( ω), which, when measured over a frequency range of Hz to GHz, enables the convenient determination of the macroscopic and microscopic properties of the fluids. Ferromagnetic resonance, identified by the χ′( ω) component passing from a positive to a negative value at a frequency f res, together with relaxation mechanisms, both Brownian and Néel, can be readily investigated. The latter components can be determined from maxima occurring in a plot of χ″( ω) against frequency and enable the effective particle radius of the suspension to be estimated. From measurements of χ( ω) one can also investigate magnetic losses arising in the fluids. An alternative method for determining the effective particle size is the principal or differential susceptibility technique. This fixed frequency technique consists of applying an external DC polarizing magnetic field, H 0, to the ferrofluid sample contained within a cylindrical coil and measuring the parallel, χ ∥( H 0), and perpendicular, χ ⊥( H 0), incremental susceptibility components. In this paper, a brief review is given of the above-mentioned topics and examples of results obtained, presented.

Application of magnetic fluids in tribotechnical systems

This paper presents the results of investigations on applications of magnetic fluids as lubricant. Magnetic fluids can be used as lubricants in gears, plain bearings and roller bearings. With an appropriate designed magnetic field the lubricants can be fixed at those places, where they are needed. The main advantage of the use of magnetic fluids as lubricant is based on the considerable reduction of the maintenance for the lubricant supply, because the lubricant is prevented from leaving the contact zone of the tribological system. Further advantages are the small amount of the necessary lubricant and the avoidance of leakages. The rheological and tribological behaviour of magnetic fluids was investigated and compared with conventional lubricants between friction pairs under boundary conditions.

Magnetic systems depending on three or two variables; thermodynamic analysis and some existing and possible applications

Until quite recently, the theory of continuous media dealt mainly with diamagnetic and paramagnetic fluids. The researchers did not consider strongly magnetizable fluids, probably because such media had not yet been discovered in natural conditions and did not exist until recently as manufactured products. However, in the early 1960 s, magnetic fluids (MF) could be synthetically prepared, and then, technological interest in MF grew rapidly. Besides, magnetic refrigeration has been used for over 60 years as a technology to achieve temperatures below 1 K, employing the magnetocaloric effect of some solid materials. However, in the last 20 years, the technology has been developing for refrigeration applications above 1 K up to and including heat pumps above room temperature. The work has been multinational in scope and has focussed on the analysis of magnetic thermodynamic systems, investigation of magnetic materials suitable for refrigerants and development of prototype refrigerators. After a synthetic review of the basic properties of MF, of magnetic refrigerators and heat pumps and of magnetic properties of living matter, the aim of this paper is a thermodynamic examination of these systems in comparison with the relations usually applied to fluids. Three independent variables are generally considered, whereas usually only two variables have been considered until now for what is known to the authors. Also, in the case of only two independent variables, some results are obtained which are original. Furthermore, some applications of MF are taken into account, in particular, possibilities of converting thermal into mechanical energy are examined.

Magnetic fluid composites and tools for microgravity experiments

Microgravity conditions offer the natural environment for the research and applications of magnetic fluids, in particular for magnetic fluid composites. The nonmagnetic solid component of the composite needs no more magnetic stabilization, and the material becomes macroscopically homogeneous. Small external physical fields may produce relevant effects of ordering and act upon the internal organization and the properties of the fluid. Results are given for applications in inertial and gravitational sensors.

磁性流体 磁性流体工学の最近の展開

A recent development in magnetic fluids research is reviewed. The research activities in this field are increasing accompanied with the success of the synthesis of magnetic fluids with excellent magnetic properties. Apparent viscosity and rheological properties are discussed in connection with the particle aggregates in the applied magnetic field. As the thermo-fluid dynamics of magnetic fluids, recent investigations on the pipe flow problems and heat transfer control are taken up. Finally, as the representative examples of recent studies on the applications of magnetic fluids, various sensors, actuators, grinding device and heat pipe are explained.