Ferrofluid Flow Research Articles

Study of ferrofluid flow and heat transfer between cone and disk

Abstract This paper investigates the flow of water-based Fe3O4 ferrofluid flow and heat transfer due to rotating cone and disk under the influence of the external magnetic field. The similarity approach is used to transform the governing equations of ferrohydrodynamic flow into a set of nondimensional coupled differential equations. The nondimensional coupled differential equations are solved numerically through the finite element procedure. Effect of rotation of the disk, rotation of the cone, the intensity of the magnetic field, volume concentrations, and Prandtl number are analyzed on the velocity and temperature distributions. These effects are also observed on the skin friction coefficients and local heat transfer rate. The rotation of the disk, rotation of the cone, and the intensity of the magnetic field have a major impact on the velocity profiles, temperature profiles, skin friction coefficients, and local heat transfer rate.

Analytical model for electromagnetic induction in pulsating ferrofluid pipe flows

Energy harvesting processes using ferrofluidic induction—a process that generates voltage via the pulsation of a ferrofluid (iron-based nanofluid) through a solenoid—have received increasing attention over the past decade. In this paper an analytical model is proposed to predict the induced electromotive force (EMF) based on the flow behavior and magnetic properties of a pulsating ferrofluid energy harvesting device. The ferrofluid is treated as an idealized series of discrete magnetic ‘slugs’ within passing through the solenoid, and the model identifies key parameters for describing and optimizing ferrofluidic induction in pulsating pipe flows. The resulting expression for induced EMF as a function of slug position relative to the solenoid is numerically integrated to determine the root mean square (RMS) of EMF during one pulsation cycle. Data from a previously documented study using an experimental induced EMF test rig is analyzed to find corresponding measured values of EMF RMS and used to validate the analytical model. Experimental and analytical results both show an increase in induced EMF with higher pulse frequency, increased number of bias magnets, and reduced spacing between the magnet and solenoid. At low magnetic flux densities and pumping frequencies, the EMF is negligible; with 0.3 mT magnetic flux density and 9 and 18 Hz pumping frequencies the measured RMS is nominally zero. For a 9 Hz pumping frequency the RMS value of the induced EMF is less than 1 μV at all magnetic flux densities. For the highest pumping frequency examined, 30 Hz, the induced EMF RMS is greater than 1 μV for all magnetic flux densities greater than 0.7 mT. As the experimentally measured values of EMF lie within the uncertainty bounds of the model, induced EMF can be predicted within an order of magnitude for magnetic fluid-induced energy harvesting systems.

Nanoparticles shape effects on thermal performance of Brinkman-type ferrofluid under heat injection/consumption and thermal radiation: A fractional model with non-singular kernel and non-uniform temperature and velocity conditions

The prime aim of this article is the construction of a fractional model to enhance the heat transfer rate for magnetohydrodynamic (MHD) convectional transport of ferrofluid by applying the time-fractional concept of Caputo-Fabrizio derivative on Brinkman-type fluid model. Kerosene oil and water are considered to serve as carrier fluids for iron oxide (Fe3O4) nanoparticles of various non-spherical shapes (brick, cylinder, platelet, and blade). The non-uniform time-dependent motion of an unbounded upward plate causes to generate the flow of ferrofluid. The supplementary physical phenomena such as ramped heating, thermal radiation, and heat injection/consumption are also analyzed. In addition, the effectiveness of using differently shaped Fe3O4 nanoparticles for heat transfer and ferrofluid flow is evaluated. The exact solutions for non-integer order modeled differential equations are computed by employing the Laplace transform method. The comparative graphical illustrations for ramped and constant (isothermal) velocity and temperature conditions are prepared to scrutinize the impacts of several associated thermal and physical quantities. Besides, the outcomes of numerical simulations of Nusselt number and shear stress are communicated through multiple tables for an in-depth analysis. It is perceived that blade and platelet shaped Fe3O4 nanoparticles are more effective to enhance the thermal efficiency of Brinkman-type ferrofluid in contrast to cylinder and brick shaped nanoparticles. It is interesting to report that an improvement of 13.80% in Nusselt number is observed for water based ferrofluid that significantly advances its thermal properties. The fractional parameter γ produces inverse variations in momentum boundary layer thickness for isothermal and ramped plate cases. Additionally, velocity and temperature curves for ramped plate case are always lower than those of isothermal plate case. This fact highlights the importance of plate ramping in heat and flow control problems.

Spectral simulation to investigate the effects of nanoparticle diameter and nanolayer on the ferrofluid flow over a slippery rotating disk in the presence of low oscillating magnetic field

AbstractThis article explores the impacts of the solid–liquid interfacial layer and nanoparticle diameter on the unsteady ferrous‐water nanoliquid flow over a spinning disk. The existence of velocity slip is presumed on the disk. Additionally, the low oscillating magnetic field effect is included to extract the hydrothermal consequences of the problem. Shliomis theory has been presented to verbalize the foremost equations of the mentioned flow problem. The similarity transformation renders the dimensionless equations. Spectral quasilinearization technique along with the residual error profile is presented to resolve the converted equations. An adequate number of pictures and tables are portrayed to improve the parametric study of the problem. Several streamlines, isotherms, contour plots, and three‐dimensional figures are presented to disclose the hydrothermal integrity of the nanofluidic transport. Effective magnetization parameter produces 4.67% skin frictional increment. Heat transport declines for nanoparticle diameter but is enhanced for nanolayer conductivity ratio. The presence of an oscillating magnetic field always promotes heat transference as compared with the absence of the oscillating field. The nanolayer conductivity ratio conveys the highest 8.69% heat transport rate, whereas the magnetization factor provides the lowest, 1.79%. It has novel applications in magnetic drug targeting, hard disk scaling, magnetic resonance imaging, spin coating, lubrication, and so forth.

Numerical study of two-phase flow in a square cavity under magnetic field of parallel wires

In this paper, a two-phase model is administered to investigate natural convection of Fe3O4–water ferrofluid in a square cavity and under turbulent regime. Ferrofluid flow is exposed to magnetic fields which are induced by two parallel current-carrying wires. The left and right walls of the cavity are maintained at constant temperatures of $${T}_{h}$$ and $${T}_{c}$$ respectively, while the other walls are insulated. In this study, Buongiorno’s two-phase model is modified for considering the nanoparticle diffusion via turbulent eddies and magnetophoresis effects. The Reynolds-averaged Navier–Stokes equations are treated based on v2–f model and the governing equations are solved by the SIMPLE-based finite volume method. The computations are performed for various Rayleigh numbers ( $${10}^{7}$$ , $$5\times 10^{7}$$ and $${10}^{8}$$ ), nanoparticle's volume fraction ( $$0\le {\phi }_{m}\le 0.06$$ ) and magnetic numbers ranging from 0 to $$3.4 \times {10}^{11}$$ . Numerical results indicate that heat transfer rate and turbulence intensity can be significantly enhanced by the applied magnetic fields. However, the effect of employed magnetic field on heat transfer increment is more pronounced at low Rayleigh numbers.

Entropy generation and heat transfer analysis for ferrofluid flow between two rotating disks with variable conductivity

Present model analyze the flow and heat transfer of water-based carbon nanotubes (CNTs) [Formula: see text] ferrofluid flow between two radially stretchable rotating disks in the presence of a uniform magnetic field. A study for entropy generation analysis is carried out to measure the irreversibility of the system. Using similarity transformation, the governing equations in the model are transformed into a set of nonlinear coupled differential equations in non-dimensional form. The nonlinear coupled differential equations are solved numerically through the finite element method. Variable viscosity, variable thermal conductivity, thermal radiation, and volume concentration have a crucial role in heat transfer enhancement. The results for the entropy generation rate, velocity distributions, and temperature distribution are graphically presented in the presence of physical and geometrical parameters of the flow. Increasing the values of ferromagnetic interaction number, Reynolds number, and temperature-dependent viscosity enhances the skin friction coefficients on the surface and wall of the lower disk. The local heat transfer rate near the lower disk is reduced in the presence of Harman number, Reynolds number, and Prandtl number. The ferrohydrodynamic flow between two rotating disks might be useful to optimize the use of hybrid nanofluid for liquid seals in rotating machinery.

Thermal Transport in Laminar Convective Flow of Ferrofluids in the Presence of External Magnetic Field

Abstract A three-dimensional (3D) numerical investigation is carried out to examine the effect of magnetic field (MF) on laminar forced convection of ferrofluids. Laminar flow (Reynolds number (Re) ≤ 100) of ferrofluid is modeled in a square mini-channel of 2 mm hydraulic diameter in the presence of the MF. A magnetic force is induced in ferrofluids because of the applied MF, which accelerates the upstream flow and decelerates the downstream flow with respect to the magnet's location. The acceleration/deceleration of the flow disrupts the hydrodynamic and thermal boundary layers (BLs), positively affecting the heat transfer. The extent of magnetic influence primarily depends on the Reynolds number and induced magnetic force. At low Re (= 25), where magnetic force dominates over inertial force, the flow of ferrofluid is strongly affected by the MF. This results in a higher augmentation in convective heat transfer. As the Re of the flow is increased to Re = 75, the inertial forces partially overcome the effect of the magnetic force, resulting in a smaller augmentation. The interaction of magnetic and inertia forces is expressed through a dimensionless magnetic Froude number (Frm). The effect of volumetric concentration of nanoparticles, Reynolds number, and the presence of multiple magnets placed along the flow channel on heat transfer is investigated through a parametric study. A correlation has also been proposed to predict the net enhancement in the Nusselt number due to the application of the MF based on the results of the present study.

Numerical Study of Mixing and Mass Transfer in a Micromixer by Stimulation of Magnetic Nanoparticles in a Magnetic Field

AbstractA numerical study on the hydrodynamics of ferrofluid flow and mass transfer characteristics in a Y‐type micromixer is performed. Computational fluid dynamics (CFD) simulation is accomplished to survey the behavior of ferrofluid flow subject to an external magnetic field and to specify its effect on the mass transfer between two immiscible liquid phases. The geometric reconstruction scheme (Geo‐Reconstruct) based on piecewise linear interpolation is applied to reconstruct the two‐phase interface. The results of CFD modeling are validated by experimental data, and good agreements are achieved, with a maximum relative error for the extraction efficiency of about 7.52 %. This research work shows that ferrofluid stimulation by a magnetic field can be an efficient mixing factor in microdevices.

Heat Transfer Study of the Ferrofluid Flow in a Vertical Annular Cylindrical Duct under the Influence of a Transverse Magnetic Field

We studied the laminar fully developed ferrofluid flow and heat transfer phenomena of an otherwise magnetic fluid into a vertical annular duct of circular cross-section and uniform temperatures on walls which were subjected to a transverse external magnetic field. A computational algorithm was used, which coupled the continuity, momentum, energy, magnetization and Maxwell’s equations, accompanied by the appropriate conditions, using the continuity–vorticity–pressure (C.V.P.) method and a non-uniform grid. The results were obtained for different values of field strength and particles’ volumetric concentration, wherein the effects of the magnetic field on the ferrofluid flow and the temperature are revealed. It is shown that the axial velocity distribution is highly affected by the field strength and the volumetric concentration, the axial pressure gradient depends almost linearly on the field strength, while the heat transfer significantly increases due to the generated secondary flow.

Radiated magnetic flow in a suspension of ferrous nanoparticles over a cone with brownian motion and thermophoresis

A theoretical investigation is executed for exploring the flow, heat and mass transfer behavior of magnetohydrodynamic radiated ferrofluid flow caused by a cone in the existence of non-uniform heat source/sink. Dispersion of ferrous nanoparticles finds applications in heat exchanger system, recharge able batteries, chemical catalysts, metallurgy, conducting paints, magnetic recording media, drug delivery, nanofibers, textiles etc. in this study we have used the two types of temperatures namely water (At 10 °C and 50 °C), having less thermal conductivity as compared with magnetic nanoparticles (CoFe2O4). A simulation is performed by mixing of cobalt ferrous particles in base fluid water with different temperatures. Also, we presented dual solutions for flow over a cone with CoFe2O4+water at 10 °C and CoFe2O4+water at 50 °C. Governing equations are solved using Runge-Kutta with shooting method and compared with published literature. From the formulated model we found that the friction factor coefficient and rate of heat transfer is more in mixture of CoFe2O4+water at 10 °C case compare to CoFe2O4 +water at 50 °C case. Similarly the mass transfer rate is more in CoFe2O4 +water at 50 °C when compared to CoFe2O4 +water at 10 °C case. These results help us to conclude that depending on the industrial appliances we can use heating or cooling processes CoFe2O4 +water at 10 °C and CoFe2O4 +water at 10 °C fluids respectively.

Irreversibility minimization analysis of ferromagnetic Oldroyd-B nanofluid flow under the influence of a magnetic dipole

Studies highlighting nanoparticles suspensions and flow attributes in the context of their application are the subject of current research. In particular, the utilization of these materials in biomedical rheological models has gained great attention. Magneto nanoparticles have a decisive role in the ferrofluid flows to regulate their viscoelastic physiognomies. Having such substantial interest in the flow of ferrofluids our objective is to elaborate the melting heat transfer impact in a stretched Oldroyd-B flow owing to a magnetic dipole in the presence of entropy generation optimization. Buongiorno nanofluid model expounding thermophoretic and Brownian features are considered. Moreover, activation energy with chemical reaction is also considered. The Cattaneo–Christov heat flux model is affianced instead of conventional Fourier law. The renowned bvp4c function of MATLAB is utilized to handle the nonlinearity of the system. Impacts of miscellaneous parameters are portrayed through graphical fallouts and numeric statistics. Results divulge that the velocity and temperature profiles show the opposite trend for growing estimates of the ferromagnetic parameter. It is also noticed that the temperature ratio parameter diminishes the entropy profile. Moreover, it is seen that the concentration profile displays a dwindling trend for the Brownian motion parameter and the opposite trend is witnessed for the thermophoretic parameter.

On the ridge of instability in ferrofluidic Couette flow via alternating magnetic field

There is a huge number of natural and industrial flows, which are subjected to time-dependent boundary conditions. The flow of a magnetic fluid under the influence of temporal modulations is such an example. Here, we perform numerical simulations of ferrofluidic Couette flow subject to time-periodic modulation (with frequency Omega _H) in a spatially homogeneous magnetic field and report how such a modulation can lead to a significant Reynolds number Re enhancement. Consider a modified Niklas approximation we explain the relation between modulation amplitude, driving frequency and stabilization effect. From this, we describe the system response around the primary instability to be sensitive/critical by an alternating field. We detected that such an alternating field provides an easy and in particular accurate controllable key parameter to trigger the system to change from subcritical to supercritical and vice versa. Our findings provide a framework to study other types of magnetic flows driven by time-dependent forcing.

Analyses of thermal performance and pressure drop in a plate heat exchanger filled with ferrofluids under a magnetic field

This paper experimentally investigates the effect of various magnetic fields on the performance of a plate heat exchanger filled with ferrofluids. Spherical nanoparticles Fe3O4 with an average diameter of 20 nm are dispersed into DI-water to synthesize the ferrofluid. Thermal performance and flow characteristics of the ferrofluid with 0.1% particle concentration are investigated based on various arrangements of magnets outside the plate heat exchanger. Effects of magnetic field strength and distribution are thoroughly studied concerning the performance of the heat exchanger with various ferrofluid flow rates. Results indicate that with a vertical arrangement of two magnets side by side outside the sidewalls, 21.8% increase in average Nusselt number and 10.0% reduction in average pressure drop are achieved compared to the cases without a magnetic field. Novel configurations of magnets are first discussed in a plate heat exchanger. Ferrofluid flow control is achieved under a measurable magnetic field strength and different flow rates. It is well known that enhancement of thermal performance in the plate heat exchanger is accompanied with a reduction of resistance loss. Deposition of magnetic particles and blockage in the channel of the plate heat exchanger will also be weakened based on results from this research.

Heat transfer from a ferrofluid during generalized Couette flow through parallel plates in the presence of an orthogonal magnetic field

In the present work, we report heat transfer during the unidirectional laminar flow of ferrofluids in a parallel plate channel in the presence of a homogeneously applied magnetic field perpendicular to the flow direction. We have considered generalized Couette flow which results from the combination of shear stress, due to the relative motion between the parallel plates, and applied pressure gradient. For a comprehensive investigation, four different thermal boundary conditions have been considered. The application of magnetic field modifies the viscosity of the colloidal ferrofluid and thereby causes variations in the local flow field. Further, it also modifies the thermal conductivity of the fluid by changing particle orientation. As a consequence, the temperature distribution between the parallel plate channel is uniquely modified. The complex interplay between the hydrodynamics and the magnetics results in implicitly coupled governing differential equations, which have been solved numerically. We report that the local temperature in the domain could be reduced by increasing the applied field strength irrespective of the imposed thermal boundary conditions. However, the influence of the applied field finally gets saturated. We also discuss the effect of Brinkman number, loading of magnetic particles and pressure gradient on temperature distribution. Finally, analytical solutions, which presents closed-form expressions of the temperature profiles for four different types of boundary conditions, have been proposed.

MHD natural convection and entropy generation of non-Newtonian ferrofluid in a wavy enclosure

Two-dimensional laminar magneto-hydrodynamic (MHD) natural convection flow of non-Newtonian ferrofluid has been investigated to understand the characteristics of heat transfer, streamlines, isotherms, and entropy generation in a wavy enclosure using the finite volume method (FVM). The horizontal boundaries of the cavity are assumed to be thermally adiabatic, while the temperatures of the left and right vertical walls are presumed to be TH and TC, respectively. The rheology of the nanofluid is represented through the power-law model, and the density variations due to thermal expansion lie within the framework of the Boussinesq approximation. Numerical simulations have been carried out for a range of dimensionless parameters such as Rayleigh number (Ra=103,104,105), Hartmann number (Ha=0,10,20), power-law index (n=0.6,0.8,1.0,1.2,1.4), volume fraction (ϕ=0,0.05,0.1), and Prandtl number Pr = 6.8377. Results indicate that the isotherms of the shear-thinning fluid are dominated by thermal convection, whereas conduction is more pronounced for shear-thickening fluids. The average Nusselt number of the non-Newtonian ferrofluid increases with the attenuation of the Hartmann number and augmentation of the Rayleigh number, and in our entire simulation, the maximum value of Nu¯, due to the addition of ferro-particles, is found to be 8.07. The power-law index has a remarkable influence on the streamlines, and ψmax tends to decrease when n is increased gradually from shear-thinning to shear-thickening fluid behavior. Moreover, it is revealed that the heat transfer rate of ferrofluid (ϕ=10%) increases up to 26% for the shear-thinning case and 25% for the shear-thickening case, under the influence of the magnetic field. Further, it is inferred that the irreversibility due to heat transfer, fluid friction, and magnetic field for the shear-thinning, Newtonian and shear-thickening ferrofluids, can be minimized based on the optimal parametric combination. The increment of Hartmann number results in 60% attenuation of total entropy for shear-thinning fluid and 9% diminution for the shear-thickening case. With the augmentation of the power-law index, the entropy generation is found to decrease by 80% in the absence of the magnetic field effect and by 54% in the presence of it. A new correlation for the average Nusselt number is proposed for the shear-thinning fluids and shows a good agreement between the computed and predicted results.

Micropolar ferrofluid flow via natural convective about a radiative isoflux sphere

Current investigation scrutinizes the magnetohydrodynamic (MHD) natural convection flow of micropolar ferrofluid across an isoflux sphere with the impacts of thermal radiation and partial slip. Cobalt-nanoparticles with kerosene as the base fluid are considered. The governing partial differential conservation equations and convenient boundary conditions are rendered into a nondimensional form. The finite difference method (FDM) is then applied to determine the solution of a collection of resultant equations. The outcomes obtained by FDM have also compared with cited investigation. Illustrations describing influences of prominent parameters which provides physical interpretations of velocity, angular velocity, and temperature fields as well as the skin friction coefficient and Nusselt number are examined in detail with the help of graphical representations. This investigation determined that the skin-friction coefficient and heat transport rate reduced along with augmentation in the magnetic force and micropolar parameter, while opposite performance is adhered with elevating in the thermal radiation. Moreover, the boosted nanoparticle volume fraction reduced the skin friction coefficient and improved the Nusselt number.

Propagating vortices in ferrofluidic Couette flow under magnetic fields – Part I: Axial and symmetry breaking transversal orientated fields

Numerical investigations of propagating vortex states (pVs) for ferrofluidic Couette flow with small aspect ratio and fixed non-rotating end-walls are presented. We study structural modifications and changes in spatial and temporal behavior for pV solutions. The system is subjected to either pure axial or pure transverse magnetic field, with the latter already breaking the basic system symmetries. While under axial magnetic field pVs remain basically the same, they are found to appear in various configurations with different symmetry variation in flow structure and flow dynamics under symmetry breaking transversal magnetic field. pVs appearing in a pitchfork bifurcation are found either symmetric or asymmetric/alternating, regarding the full cycle of vortex generation, propagation and annihilation, in upper and lower system half.

Propagating vortices in ferrofluidic Couette flow under magnetic fields – Part II: Oblique orientated fields

This work provides a numerical investigations of propagating vortex flow states (pVs) for ferrofluidic Couette flow with small aspect ratio and fixed non-rotating end-walls. The system is subjected to oblique magnetic fields as superposition of axial and transverse orientated fields. Such field configuration breaks the basic system symmetries and renders all flow structures to be inherently three-dimensional with complexer flow dynamics. Under oblique field configuration pV states are not direct present at onset. Instead oscillating flow states (oVs) bifurcate out of the stationary state. Basically these oVs hold same symmetries as pVs, which eventually evolve in a smooth transformation out of the oVs. pVs under oblique fields appear periodic or quasi-periodic, which render them topological speaking to exist on either two- or one-dimensional invariant manifolds as 2-torus or limit cycle (1-torus) solutions, respectively. In detail, structural modifications and changes in spatial and temporal behavior for pV solutions are studied with changing the magnetic field strength of the applied magnetic field.

Heat transfer of ferrofluids with magnetoviscous effects

Ferrofluids have more excellent thermal performance than their carrier liquids, but the magnetoviscous effects under magnetic fields will increase the flow resistance to weaken this enhancement. We investigated the flow and convective heat transfer performance of ferrofluids in the tube under a magnetic field by the experimental method. A non-magnetic stainless-steel tube with 476 mm length and an inner diameter of 2.46 mm is used in our test. The maximum field intensity ranges from 22 to 97.2 kA/m. The friction coefficient and Nusselt number for water and ferrofluids are measured and compared under various conditions, including Reynolds number, nanoparticles concentration, magnetic field strength, heat flux, and magnets arrangement mode. The results indicate that the magnetoviscous effects induced by the external fields offset the possible convective heat transfer enhancement, which challenges the current view that ferrofluids can be used as a potential heat transfer medium, especially in a strong magnetic field.

Numerical method approach for magnetohydrodynamic radiative ferrofluid flows over a solid sphere surface

In this paper, the theoretical study on the laminar boundary-layer flow of ferrofluid with influences of magnetic field and thermal radiation is investigated. The viscosity of ferrofluid flow over a solid sphere surface is examined theoretically for magnetite volume fraction by using boundary-layer equations. The governing equations are derived by applied the non-similarity transformation then solved numerically by utilizing the Keller-box method. It is found that the increments in ferro-particles (Fe3O4) volume fraction declines the fluid velocity but elevates the fluid temperature at a sphere surface. Consequently, the results showed viscosity is enhanced with the increase of the ferroparticles volume fraction and acts as a pivotal role in the distribution of velocity, temperature, reduced skin friction coefficient, and reduced Nusselt number of ferrofluid.