Ferrofluid Research Papers - Academia.edu (original) (raw)

This paper presents a summary of research to utilise the massive amount of low grade heat energy, for instance which exists in the worlds oceans, by a new type of magnetic cycle. Developed herein are methods based on 2nd order phase... more

This paper presents a summary of research to utilise the massive amount of low grade heat energy, for instance which exists in the worlds oceans, by a new type of magnetic cycle. Developed herein are methods based on 2nd order phase changes that make it possible to achieve high efficiency despite small temperature differences with the reservoir. Ferrofluids displaying temporary magnetic remanence are an almost perfect embodiment of the working substance for these cycles. Standard Kinetic Theory, Thermodynamic and Electrodynamic analysis and experiment validates the new cycle.

In the present study a mathematical model of biomagnetic fluid dynamics (BFD), suitable for the description of the Newtonian blood flow under the action of an applied magnetic field, is proposed. This model is consistent with the... more

In the present study a mathematical model of biomagnetic fluid dynamics (BFD), suitable for the description of the Newtonian blood flow under the action of an applied magnetic field, is proposed. This model is consistent with the principles of ferrohydrodynamics and magnetohydrodynamics and takes into account both magnetization and electrical conductivity of blood. As a representative application the laminar, incompressible, three-dimensional, fully developed viscous flow of a Newtonian biomagnetic fluid (blood) in a straight rectangular duct is numerically studied under the action of a uniform or a spatially varying magnetic field. The numerical results are obtained using a finite differences numerical technique based on a pressure-linked pseudotransient method on a collocated grid. The flow is appreciably influenced by the application of the magnetic field and in particularly by the strength and the magnetic field gradient. A comparison of the derived results is also made with those obtained using the existing BFD model indicating the necessity of taking into account the electrical conductivity of blood.

The laminar incompressible fully developed biomagnetic (blood) flow in a curved square duct under the influence of an applied magnetic field is studied. The mathematical formulation is based on the model of biomagnetic fluid dynamics... more

The laminar incompressible fully developed biomagnetic (blood) flow in a curved square duct under the influence of an applied magnetic field is studied. The mathematical formulation is based on the model of biomagnetic fluid dynamics which is consistent with the principles of ferrohydrodynamics.
According to this formulation blood is considered as an electrically nonconducting, homogeneous, and Newtonian magnetic fluid. For the numerical solution of the problem, which is described by a coupled, nonlinear system of partial differential equations, with their appropriate boundary conditions, the SIMPLE method is used. The results indicate that the axial velocity as well as the secondary flow at the transverse plane are appreciably influenced and indicate that the magnetic field could be used for controlling the blood flow by magnetic means

Nickel zinc ferrite nanoparticles NixZn1xFe2O4 (x=0.1, 0.3, 0.5) have been synthesized by a chemical co-precipitation method. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, electron... more

Nickel zinc ferrite nanoparticles NixZn1xFe2O4 (x=0.1, 0.3, 0.5) have been synthesized by a chemical
co-precipitation method. The samples were characterized by X-ray diffraction, Fourier transform
infrared spectroscopy, electron paramagnetic resonance, dc magnetization and ac susceptibility
measurements. The X-ray diffraction patterns confirm the synthesis of single crystalline NixZn1xFe2O4
nanoparticles. The lattice parameter decreases with increase in Ni content resulting in a reduction in
lattice strain. Similarly crystallite size increases with the concentration of Ni. The magnetic
measurements show the superparamagnetic nature of the samples for x=0.1 and 0.3 whereas for
x=0.5 the material is ferromagnetic. The saturation magnetization is 23.95 emu/g and increases with
increase in Ni content. The superparamagnetic nature of the samples is supported by the EPR and ac
susceptibility measurement studies. The blocking temperature increases with Ni concentration. The
increase in blocking temperature is explained by the redistribution of the cations on tetrahedral (A) and
octahedral (B) sites.

In this study, the fundamental problem of the biomagnetic (blood) fluid flow in a channel with stenosis under the influence of a steady localized magnetic field is studied. The mathematical model used for the formulation of the problem is... more

In this study, the fundamental problem of the biomagnetic (blood) fluid flow in a channel with stenosis under the influence of a steady localized magnetic field is studied. The mathematical model used for the formulation of the problem is consistent with the principles of ferrohydrodynamics (FHD) and magnetohydrodynamics (MHD). Blood is considered as a homogeneous Newtonian fluid and is treated as an electrically conducting magnetic fluid which also exhibits magnetization. For the numerical solution of the problem, which is described by a coupled, non-linear system of PDEs, with appropriate boundary conditions, the stream function–vorticity formulation is adopted. The solution is obtained by the development of an efficient pseudotransient numerical methodology using finite differences. This methodology is based on the development of a semi-implicit numerical technique, transformations and stretching of the grid and proper construction of the boundary conditions for the vorticity. Results concerning the velocity and temperature field, skin friction and rate of heat transfer indicate that the presence of the magnetic field influences the
flow field considerably.

Nanocrystalline Fe3O4 particles of controlled size were synthesized by a facile chemical co-precipitation method. The X-ray diffraction patterns confirm the synthesis of single crystalline phase of Fe3O4 nanoparticles with lattice... more

Nanocrystalline Fe3O4 particles of controlled size were synthesized by a facile chemical co-precipitation method. The X-ray
diffraction patterns confirm the synthesis of single crystalline phase of Fe3O4 nanoparticles with lattice parameter 8.4090 Å.
The average particle size of as-synthesized sample is 11.5 nm. A TEM analysis show that the sample contains well dispersed
nanoparticles of almost spherical in shape with average particle size is of the order of 10-20 nm. The magnetic measurements
show superparamagnetic nature of the sample. The saturation magnetization is 63emu/g. The rheological study of oleic acid
coated Fe3O4 ferrofluid show magneto-viscous effect. In the absence of the magnetic field, the ferrofluids behave essentially as
a Newtonian fluid having a rate-insensitive viscosity whereas increase in the magnetic field leads to strong changes in the
viscosity. This can be attributed to the formation of chain-like clusters due to strong inter-particle interaction in the presence of
a magnetic field.

Although the compression ignition engines are a significant source of power, their detrimental emissions create considerable problems to the environment as well as to humans. The objective of the present experimental investigation is to... more

Although the compression ignition engines are a significant source of power, their detrimental emissions create considerable problems to the environment as well as to humans. The objective of the present experimental investigation is to examine the effects of the magnetic nanofluid fuels on combustion performance characteristics and exhaust emissions. In this regard, the Fe3O4 nanoparticles dispersed in the diesel fuel with the nanoparticle concentrations of 0.4 and 0.8 vol% were employed for combustion in a single-cylinder, direct-injection diesel engine. After a series of experiments, it was demonstrated that the nanoparticle additives, even at very low concentrations, have considerable influence in diesel engine characteristics. Furthermore, the results indicated that the nanofluid fuel with nanoparticle concentration of 0.4 vol% shows better combustion characteristics in comparison with that of 0.8 vol%. Based on the experimental results, NO x and SO2 emissions dramatically reduce, while CO emissions and smoke opacity noticeably increase with increasing the dosing level of nanoparticles.

Findings of an experimental study evaluating the effect of γ (gamma) and α (alpha) Fe2O3/ Kerosene nanofluids for a closed loop pulsating heat pipe for heat inputs from 10 to 150 W under magnetic field is presented in the present study.... more

Findings of an experimental study evaluating the effect of γ (gamma) and α (alpha) Fe2O3/ Kerosene nanofluids for a closed loop pulsating heat pipe for heat inputs from 10 to 150 W under magnetic field is presented in the present study. The nanoparticles had a size ranged from 10 nm to 30 nm. The heat transfer rate and the temperature distribution of the heat pipe were examined with and without the magnetic field. Likewise, the Fe2O3 base nanofluids were exposed to a magnetic field to measure the vapor temperature at the center of the pulsating heat pipe directly. The results showed that both heat transfer coefficient and thermal performance of the pulsating heat pipe are enhanced by the addition of Fe2O3 nanoparticles, especially when the magnetic field is present. The increased input heat flux rises the heat transfer coefficient of the condenser and the evaporator. Lower evaporator heat transfer coefficient and higher temperature difference between condenser and evaporator are seen because of α- Fe2O3 nanoparticles as compared to γ- Fe2O3 nanoparticles. Among six nanoparticles investigated in this research, the optimum type and size of Iron oxide nanoparticles under similar conditions for attaining the best heat transfer performance was 20 nm γ-Fe2O3 nanoparticles.

In this paper we investigate the use of a linear ratiometric Hall sensor as a non-contact position transducer to measure small displacement of a ferrofluid magnetic actuator. The experimental setup requires a small permanent magnetic disc... more

In this paper we investigate the use of a linear
ratiometric Hall sensor as a non-contact position transducer to
measure small displacement of a ferrofluid magnetic actuator.
The experimental setup requires a small permanent magnetic
disc attached to the actuator’s rod and a fixed mounted Hall
Effect sensor in the proximity of the magnet. Analog data from
the sensor is acquired through an Arduino board, which is an
open source electronics platform, converted to distance after a
calibration method through a lookup table and plotted through
dedicated graphics software. The setup allows to measure with a
precision to 0.1 mm the position of the actuator’s rod and to plot
the static characteristic of the displacement for a range up to
±5mm.

The present work is dedicated to analyze the flow and heat transport of ferrofluids along a flat plate subjected to uniform heat flux and slip velocity. A magnetic field is applied in the transverse direction to the plate. Moreover, three... more

The present work is dedicated to analyze the flow and heat transport of ferrofluids along a flat plate subjected to uniform heat flux and slip velocity. A magnetic field is applied in the transverse direction to the plate. Moreover, three different kinds of magnetic nanoparticles (Fe3O4, CoFe2O4, Mn-ZnFe2O4) are incorporated within the base fluid. We have considered two different kinds of base fluids (kerosene and
water) having poor thermal conductivity as compared to solid magnetic nanoparticles. Self-similar solutions are obtained and are compared with the available data for special cases. A simulation is performed for each ferrofluid mixture by considering the dominant effects of slip and uniform heat flux. It is found that the present results are in an excellent agreement with the existing literature. The variation of skin friction and heat transfer is also performed at the surface of the plate and then the better heat transfer and of each
mixture is analyzed. Kerosene-based magnetite Fe3O4 provides the higher heat transfer rate at the wall as compared to the kerosene-based cobalt ferrite and Mn-Zn ferrite. It is also concluded that the primary effect of the magnetic field is to accelerate the dimensionless velocity and to reduce the dimensionless surface temperature as compared to the hydrodynamic case, thereby increasing the skin friction and the
heat transfer rate of ferrofluids.

The paper presents an experimental study of the capillary electrostatic instability occurring under effect of a constant electric field on a magnetic fluid individual peak. The peaks under study occur at disintegration of a magnetic fluid... more

The paper presents an experimental study of the capillary electrostatic instability occurring under effect of a constant electric field on a magnetic fluid individual peak. The peaks under study occur at disintegration of a magnetic fluid layer applied on a flat electrode surface under effect of a perpendicular magnetic field. The electrocapillary instability shows itself as an emission of charged drops jets from the peak point in direction of the opposing electrode. The charged drops emission repeats periodically and results in the peak shape pulsations. It is shown that a magnetic field affects the electrocapillary instability occurrence regularities and can stimulate its development. The critical electric and magnetic field strengths at which the instability occurs have been measured; their dependence on the peak size is shown. The hysteresis in the system has been studied; it consists in that the charged drops emission stops at a lesser electric (or magnetic) field strength than that of the initial occurrence. The peak pulsations frequency depending on the magnetic and electric field strengths and on the peak size has been measured.

In this paper, we investigated the combined effect of variable-viscosity, surface roughness, couple stress fluid, velocity-slip, and ferrofluid lubricant on the fluid-film characteristics of an infinitely wide rectangular plate... more

In this paper, we investigated the combined effect of variable-viscosity, surface roughness, couple stress fluid, velocity-slip, and ferrofluid lubricant on the fluid-film characteristics of an infinitely wide rectangular plate squeeze-film bearing. The variable-viscosity is obtained using the Barus formula and the lubricant becomes non-Newtonian due to the combination of the couple-stress fluid and the ferrofluid lubricant. The Modified Reynolds equation is used to solve the pressure distribution, where an external magnetic field produces a body force in the lubricating system. We calculated the pressure distribution and the load-carrying characteristics of the squeeze film bearing. The results indicate that the slipvelocity enhances the pressure distribution and the load-carrying capacity of the bearing. For a combination of slip-velocity and Magnetic parameters, the load and pressure distribution are greatly enhanced.

This paper investigates numerically the hydro-thermal characteristics of a ferrofluid (water and 4 vol% Fe 3 O 4) in a vertical rectangular duct which is exposed to a non-uniform transverse magnetic field generated by an electric current... more

This paper investigates numerically the hydro-thermal characteristics of a ferrofluid (water and 4 vol% Fe 3 O 4) in a vertical rectangular duct which is exposed to a non-uniform transverse magnetic field generated by an electric current going through a wire located parallelly under the duct. The two phase mixture model and the control volume technique have been used to study the flow. The results show that applying the aforementioned magnetic field increases the Nusselt number and friction factor and also creates a pair of vortices that enhances heat transfer and prevents sedimentation of nano-particles. Furthermore, unlike the axial non-uniform magnetic field, the increase of the Nusselt number for the transverse magnetic field is considerable in all length along the duct and it is also concluded that with increasing the Reynolds number, the effect of the transverse non-uniform magnetic field on the Nusselt number is more than that of the axial non-uniform magnetic field.

Abstract: Implanting recombinant cells encapsulated in alginate microcapsules to secrete therapeutic proteins has been proven clinically effective in treating several murine models of human diseases. However, once im-planted, these... more

Abstract: Implanting recombinant cells encapsulated in alginate microcapsules to secrete therapeutic proteins has been proven clinically effective in treating several murine models of human diseases. However, once im-planted, these microcapsules cannot be assessed with-out ...

In this study, the fundamental problem of the biomagnetic fluid flow in a lid driven cavity under the influence of a steady localized magnetic field is studied. The mathematical model used for the formulation of the problem is consistent... more

In this study, the fundamental problem of the biomagnetic fluid flow in a lid driven cavity under the influence of a steady localized magnetic field is studied. The mathematical model used for the formulation of the problem is consistent with the principles of Ferrohydrodynamics (FHD) and Magnetohydrodynamics (MHD). The biomagnetic fluid is considered as a homogeneous Newtonian fluid and is treated as an electrically conducting magnetic fluid which also exhibits magnetization. A known biomagnetic fluid which exhibits such magnetic properties is blood. For the numerical solution of the problem, which is described by a coupled, non linear system of PDEs, with appropriate boundary conditions, the SIMPLE algorithm is used. The solution is obtained by the development
of a numerical methodology using finite volumes on a staggered, properly stretched, grid. Results concerning the velocity indicate that the presence of the magnetic field influences considerably the flow field.

In this study, a “membrane-less and spill-less” gas-sensing device has been evaluated for the electrochemical detection of oxygen. Iron oxide magnetic nanoparticles were prepared by chemical co-precipitation and used to prepare an aqueous... more

In this study, a “membrane-less and spill-less” gas-sensing device has been evaluated for the electrochemical detection of oxygen. Iron oxide magnetic nanoparticles were prepared by chemical co-precipitation and used to prepare an aqueous ferrofluid. The iron oxide nanoparticles were subsequently stabilised and passivated with a cationic polymer, namely, poly(diallyldimethyl ammonium chloride). The resulting ferrofluid was evaluated as an electrolyte for the analytical quantification of oxygen on screen-printed carbon electrodes. An applied magnetic field immobilised the ferrofluid electrolyte in place to result in a “membrane-less and spill-less” ferrofluid-based gas sensor. The polymer poly(diallyldimethyl ammonium chloride) was found to result in an apparent enhancement in the electrocatalysis of the system towards the oxygen reduction reaction. Furthermore, as the strength of the applied magnetic field was increased, the oxygen reduction current also increased owing to the response of the polymer-coated nanoparticles. The oxygen reduction current was linear from 0 to 100 % oxygen content.

In this paper, the rapid mixing of deionized water and Fe 3 O 4 ferrofluid in a Y-shaped microchannel using a permanent magnet is studied both numerically and experimentally. The microchannel has a rectangular cross section with 500 m in... more

In this paper, the rapid mixing of deionized water and Fe 3 O 4 ferrofluid in a Y-shaped microchannel using a permanent magnet is studied both numerically and experimentally. The microchannel has a rectangular cross section with 500 m in width and 1 mm in depth. The process, assumed to be two-dimensional and steady state, is simulated by COMSOL numerical software. In the numerical simulation, the Maxwell equations are solved to obtain the magnetic potential. Then, the magnetic force can be calculated. Knowing the magnetic force, the momentum and transport-diffusion equations are solved. A setup is designed and fabricated to carry out the experiments. The mixing process is photographed by a CCD camera for 5 min until the mixing process reached a steady state condition. The numerical results are compared with the corresponding measurements to validate the simulations. The effect of different parameters such as magnetic field's strength (1280G, 2000G and 3000G), volume flow rate (30 cc/min, 40 cc/min, and 60 cc/min), and mass fraction of nanoparticles (0.0125, 0.025 and 0.05) is investigated on the mixing efficiency. Applying magnetic field considerably improves the mixing efficiency of the micromixer and reduces the mixing length. Increasing the mass fraction of nanoparticles and magnetic field strength increases the mixing efficiency until the magnetization of the ferrofluid reaches its saturated level. Increasing the fluid flow, however, lowers the mixing efficiency and increases the mixing length.

In the present work, a Chebyshev pseudospectral method for the numerical solution of the two-dimensional, laminar, incompressible, viscous flow of a biomagnetic fluid over a stretching sheet under the action of an applied magnetic field... more

In the present work, a Chebyshev pseudospectral method for the numerical solution of the two-dimensional, laminar, incompressible, viscous flow of a biomagnetic fluid over a stretching sheet under the action of an applied magnetic field and in the presence of heat transfer is applied and demonstrated. In this problem, it is assumed that the magneto-thermo-mechanical coupling is described not only by a function of temperature but by an expression involving also the magnetic field intensity. The numerical method used for the solution of the coupled and non-linear boundary value problem of ordinary differential equations, describing this physical problem, achieves high accuracy using relatively few nodal points. A comparison with numerical results, obtained by using a finite difference method is also made, showing the efficiency of the Chebyshev pseudospectral method.

Nanocrystalline Fe3O4 particles of controlled size were synthesized by a chemical coprecipitation method. X-ray diffraction patterns confirm the synthesis of single crystalline phase of Fe3O4 nanoparticles with the lattice parameter... more

Nanocrystalline Fe3O4 particles of controlled size were synthesized by a chemical coprecipitation
method. X-ray diffraction patterns confirm the synthesis of single crystalline
phase of Fe3O4 nanoparticles with the lattice parameter 8.4090 ˚A. The particle size is
11.5 nm and increases to 20 nm after annealing. TEM image shows that the sample
contains well dispersed nanoparticles with an average particle size of the order of 20 nm.
Magnetic measurements show the superparamagnetic nature of the sample that is also
confirmed by EPR measurements. The saturation magnetization is 42 emu/g. The results
are explained adequately.

An innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is... more

An innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external magnetic field, and under applied DC fields. The signals (local magnetic flux density variations) are quantified analytically, experimentally and numerically. The model agrees well with the tests, showing that the signal increases with the applied field strength, up to the saturation magnetization of the ferrofluid, and decreases with the distance to the crack longitudinal axis, and thus it can provide useful estimations of the signal. The proposed technique, requiring application of external fields to magnetize the ferrofluid to enhance the signal, seems promising: the model suggests that signals associated to cracks significantly smaller than surface cracks in a target application like aircraft skin panel inspection NASA STD-5009 are easily detectable with commercial magnetometers.

ABSTRACT The fundamental problem of biomagnetic fluid dynamics (BFD) in a 2D rectangular channel is numerically studied. The physical problem is described by a coupled, non-linear system of partial differential equations, with appropriate... more

ABSTRACT The fundamental problem of biomagnetic fluid dynamics (BFD) in a 2D rectangular channel is numerically studied. The physical problem is described by a coupled, non-linear system of partial differential equations, with appropriate boundary conditions. For the mathematical formulation, the stream function–vorticity formulation is used and the numerical solution is obtained by developing a pseudotransient numerical technique. A boundary condition for the vorticity is also constructed and grid stretching is used. The efficiency of the method is verified by comparison with other results documented in the literature. New results are also obtained for high values of the magnetic number which is the dominant factor for the determination of the flow field in biomagnetic fluid flow problems. Copyright © 2007 John Wiley & Sons, Ltd.

The influence of a magnetic field on heat transfer is studied by using the lattice Boltzmann method for a magnetic fluid (ferrofluid) flowing through a two-dimensional micro channel; to analyse the effect of the sidewalls upon the flow... more

The influence of a magnetic field on heat transfer is studied by using the lattice Boltzmann method for a magnetic fluid (ferrofluid) flowing through a two-dimensional micro channel; to analyse the effect of the sidewalls upon the flow and heat transfer, the three-dimensional version of the micro channel is also studied. This problem is of considerable interest when dealing with cooling of micro-electronic devices. The magnitude of the magnetic force is controlled by changing the electrical current through a dipole. The results indicate that the flow is relatively uninfluenced by the magnetic field until its strength is large enough for the Kelvin body force to overcome the viscous force. It was observed that the magnetic force was able to change the flow field and increase the heat transfer in the channel.

A coupled method of finite differences and boundary elements is applied to solve a nonlinear transmission problem of magnetostatics. The problem describes an interaction of a uniform magnetic field with a cylindrical ferrofluid layer.... more

A coupled method of finite differences and boundary elements is applied to solve a nonlinear transmission problem of magnetostatics. The problem describes an interaction of a uniform magnetic field with a cylindrical ferrofluid layer. Fer-rofluid magnetisations, based on expansions over the Langevin law, are considered to model ferrofluids with a different concentration of ferroparticles. The shielding effectiveness factor of the cylindrical thick-walled ferrofluid layer is calculated depending on intensities of the uniform magnetic field and on thickness of the ferrofluid layer.

In this paper, the behavior of a two-dimensional tube with an elastic segment containing ferrofluid (blood and 3 vol% Fe 3 O 4), in presence of non-uniform magnetic field is reported. Two cases of magnetic field including constant... more

In this paper, the behavior of a two-dimensional tube with an elastic segment containing ferrofluid (blood and 3 vol% Fe 3 O 4), in presence of non-uniform magnetic field is reported. Two cases of magnetic field including constant gradient (both positive and negative) and field of a wire, carrying electric current were examined. Surface tension of the membrane is considered to be fixed and constant along the elastic wall. Numerical solution of governing equations of the flow field has been obtained using the two-phase mixture model and control volume technique. Also, the membrane equation has been used to iterate and access the membrane position. Based on the obtained results, applying positive gradient magnetic field makes the tube narrower, but the negative one and magnetic field of electric wire opens the tube up.

The paper presents a ferrofluid actuator with a nonmagnetic disc, whose position can be controlled by a command current in the surrounding coils. An exact analytical expression for the force acting on the nonmagnetic disc is determined... more

The paper presents a ferrofluid actuator with a nonmagnetic disc, whose position can be controlled by a command current in the surrounding coils. An exact analytical expression for the force acting on the nonmagnetic disc is determined for a simplified model, and a numerical analysis based on FEM is also performed for the real device model. The COMSOL Multiphysics results