Ferrofluid Flow Research Articles

Numerical investigation of the magnetic field effect on the heat transfer and fluid flow of ferrofluid inside helical tube

The effect of a magnetic field on heat and fluid flow of ferrofluid in a helical tube is studied numerically. The helical tube is under constant wall temperature boundary condition. Parametric studies are done to investigate the effects of different factors such as the magnetic field gradient value and Reynolds number on heat transfer rate and pressure drop. Results indicate that the magnetic field increases the Nusselt number by about 40%. At high magnetic gradient value, Nusselt number and friction factor rise slightly, while at low magnetic gradient value, the increment of Nusselt number is considerable. Furthermore, the growth of wall shear stress on tube wall results in lower thermal–hydraulic performance at the high magnetic gradient value. There is an optimum case for thermal–hydraulic performance which results in most top performance of helical tube in the presence of the magnetic field.

Effect of different frequency functions on ferrofluid FHD flow

Abstract A finite volume method is used to investigate the unsteady thermomagnetic convection of ferrofluid flow in a miniature channel under the effect of constant and oscillating magnetic fields. A magnetic line dipole as a magnetic source is placed under the lower wall of the two-dimensional channel whose lower and upper walls are subjected to a constant heat flux. To generate the oscillating magnetic field, four different frequency functions including rectangle, sine, triangle and sawtooth functions are implemented in the constant magnetic field. The study parameters include four frequency functions, magnetic field intensity as a magnetic number (Mn = 3.833 × 108, 8.624 × 108, 1.533 × 109), frequencies (f = 0.5–5 Hz) and Reynolds numbers (Re = 20–40). Results revealed that applying the constant magnetic field enhances heat transfer and as the Reynolds number increases, the effectiveness of magnetic field on heat transfer rate diminishes. The oscillating magnetic field, regardless of the type of the applied frequency function, improves heat transfer rate due to thermal boundary layer suppression and increase in velocity field. For all applied functions, results show that there is an optimum frequency where maximum heat transfer happens and this frequency increases for higher Reynolds numbers. For rectangle and sawtooth functions with instant change in the magnetic field, two simultaneous vortexes emerges which leads to better heat transfer than sine and triangle functions. The alteration of the pressure drop in one period is proportionate with the shape of the applied frequency even though the range of the alterations reduces with the increase of the Reynolds number.

Microstructure and inertial characteristic of a magnetite Ferro fluid over a stretched sheet embedded in a porous medium with viscous dissipation using the spectral quasi-linearisation method

The innovative micropolar nanofluid is introduced in this piece of work to examine the microstructure and inertial characteristics of the substructure particles. To be more precise, the flow and heat transport of micropolar Ferro fluid over a stretched sheet embedded in a porous medium with viscous dissipation is considered. The mathematical model is formulated with the help of Tiwari–Das nanofluid model. There after a convergent spectral quasi-linearisation method is applied to work out the resulting nonlinear system of equations. The impacts of pertinent parameter on velocity, micro-rotation velocity are exposed graphically and analysed thoroughly. Finally, the numerical outcomes are compared with previously published results under special cases and found a decent agreement. Main remarks are: the outcomes demonstrate that micro-rotation velocity decreases initially and after that increases with the increment in micro-rotation parameter, and for higher values of Eckert number there is an increase in temperature.

Effect of magnetic field on the hydrodynamic and heat transfer of magnetite ferrofluid flow in a porous fin heat sink

Abstract The present study numerically investigates the effects of a uniform external magnetic field and porous fins on convective heat transfer and pressure drop of magnetite ( F e 3 O 4 /water) nanofluid in a heat sink. Effects of volume fraction, porosity, Reynolds number, and magnetic field strength on the performance of the heat sink are studied. Results indicate that heat transfer increases at high volume fractions, fin porosities and magnetic field intensities and decreases with the Reynolds number. A 13% enhancement of heat transfer is obtained for the heat sink with solid fins by using ferrofluid compared to the pure water flow. This value grows up to 35% by using porous fins and imposing magnetic field to the heat sink. Moreover, using porous fins is shown to decrease the pressure drop while the magnetic field effect is not considerable. Therefore, it is concluded that the proposed methods result in a remarkable heat transfer enhancement while decreasing the pressure drop.

Effects of Velocity and Thermal Slip Conditions with Radiation on Heat Transfer Flow of Ferrofluids

To analyze the thermal convection of ferrofluid along a flat plate is the persistence of this study. The two-dimensional laminar, steady, incompressible flow past a flat plate subject to convective surface boundary condition, slip velocity in the presence of radiation has been studied where the magnetic field is applied in the transverse direction to the plate. Two different kinds of magnetic nanoparticles, magnetite Fe3O4 and cobalt ferrite CoFe2O4 are amalgamated within the base fluids water and kerosene. The effects of various physical aspects such as magnetic field, volume fraction, radiation and slip conditions on the flow and heat transfer characteristics are presented graphically and discussed. The effect of various dimensionless parameters on the skin friction coefficient and heat transfer rate are also tabulated. To investigate this particular problem, numerical computations are done using the implicit finite difference method based Keller-Box Method.

Influence of rotating magnetic field on Maxwell saturated ferrofluid flow over a heated stretching sheet with heat generation/absorption

This article is focused on Maxwell ferromagnetic fluid and heat transport characteristics under the impact of magnetic field generated due to dipole field. The viscous dissipation and heat generation/absorption are also taken into account. Flow here is instigated by linearly stretchable surface, which is assumed to be permeable. Also description of magneto-thermo-mechanical (ferrohydrodynamic) interaction elaborates the fluid motion as compared to hydrodynamic case. Problem is modeled using continuity, momentum and heat transport equation. To implement the numerical procedure, firstly we transform the partial differential equations (PDEs) into ordinary differential equations (ODEs) by applying similarity approach, secondly resulting boundary value problem (BVP) is transformed into an initial value problem (IVP). Then resulting set of non-linear differentials equations is solved computationally with the aid of Runge–Kutta scheme with shooting algorithm using MATLAB. The flow situation is carried out by considering the influence of pertinent parameters namely ferro-hydrodynamic interaction parameter, Maxwell parameter, suction/injection and viscous dissipation on flow velocity field, temperature field, friction factor and heat transfer rate are deliberated via graphs. The present numerical values are associated with those available previously in the open literature for Newtonian fluid case (γ 1 = 0) to check the validity of the solution. It is inferred that interaction of magneto-thermo-mechanical is to slow down the fluid motion. We also witnessed that by considering the Maxwell and ferrohydrodynamic parameter there is decrement in velocity field whereas opposite behavior is noted for temperature field.

Numerical investigation of ferrofluid jet flow and convective heat transfer under the influence of magnetic sources

This work presents a numerical investigation of convective heat transfer and confined ferrofluid jet flow through a channel under the influence of six magnetic sources placed outside the system and arranged in a staggered manner. The upper and the lower walls are maintained at a constant heat flux density, while the side walls at the inlet are thermally insulated. For the ferrofluid flow, the ferrohydrodynamics (FHD) and thermophoresis effects, as well as the Brownian motion are taken into account. The governing equations are solved numerically using the finite volume method with the SIMPLE algorithm. The influence of the magnetic number (Mn), the sources position (Xi), and the jet inlet height (R) on the flow as well as on the heat transfer characteristics is analyzed. The results show that the flow structure and the thermal boundary layers development are strongly disturbed by the presence of the magnetic sources as well as the narrowing at the channel inlet. The heat transfer is enhanced with the increase of the magnetic number Mn and the reduction of the opening ratio R. It is also found that the closer the sources from the channel inlet, the higher the heat exchange, with an optimal position depending on Mn and R. Finally, the comparison between the gain in heat transfer rate and the pressure drop indicates that the case R = 1/4 and Mn = 50 leads to the most efficient system.

MHD Natural Convection Ferrofluid Flow in Semi-Annulus Enclosures

This study examines the natural convection flow and the heat transfer of a water-based ferrofluid consisting Fe3O4 nanoparticles in a semi-annulus cavity with a circular outer and sinusoidal inner walls under the effect of a magnetic field produced by multiple nodal magnetic sources. The equations governing the ferrofluid flow are numerically solved using the dual reciprocity boundary element method. That is the equations are transformed into integral equations only on the boundary by using the fundamental solution of the Laplace equation and treating all other terms as nonhomegeneity through radial basis function approximation, which results in a discretized system of small size. The numerical computations are performed for several physical parameters namely, Hartmann, Rayleigh and magnetic numbers, solid volume fraction of nanoparticles, the number of undulation and the amplitude of sinusoidal wall. The obtained results show that increasing Rayleigh number, solid volume fraction and amplitude of sine waves enhance the average Nusselt number whereas it decreases with an increase in Hartmann number.

Magnetohydrodynamic radiative liquid thin film flow of kerosene based nanofluid with the aligned magnetic field

The boundary layer analysis of liquid film flow of ferrofluids has awesome consideration due to its inexhaustible pragmatic applications in manufacturing processes. By keeping this in view, we analyzed the magnetohydrodynamic film flow of Casson fluid past an extending sheet with thermal radiation and non-uniform heat source/sink. To investigate the magnetic field effect on the flow, we applied the magnetic field at various flow directions. Dual solutions are found for kerosene-Fe3O4 and kerosene-CoFe2O4 ferrofluids. Similarity transformations are used to convert the nonlinear PDE’s as a group of nonlinear ODE’s. R-K strategy based shooting technique is utilized to solve the converted equations. Numerical estimations of the physical parameters involved in the problem are calculated for the friction factor and reduced Nusselt number. It is noticed that the heat transfer rate is high in kerosene-Fe3O4 ferrofluid when compared to kerosene-CoFe2O4 ferrofluid.

Study of heat transfer and entropy generation in ferrofluid under low oscillating magnetic field

This study presents an analytical investigation on the entropy generation in ferrofluid flow over rotating disk with influence of low oscillating magnetic field. The entropy generation equation is derived as a function of velocity and temperature gradient. This equation is non-dimensionalized by using geometrical and physical flow field-dependent parameters. Their reversibilities due to fluid flow and heat transfer and their contribution in total entropy generation are calculated under the impact of magnetic parameter and nanoparticle volume fraction. In addition, the results for average heat transfer coefficient and thermal resistance are also discussed and give a way to enhance the heat transfer rate under keeping information of entropy generation.

A two-phase simulation of convective heat transfer characteristics of water–Fe3O4 ferrofluid in a square channel under the effect of permanent magnet

In this numerical study, the hydrothermal characteristics of the water–Fe3O4 ferrofluid are investigated using the two-phase mixture model. The ferrofluid flows in a square channel and is under the effect of magnetic field produced by permanent magnet(s). A parametric study is performed to analyze the effect of different factors such as nanoparticles concentration and diameter, Reynolds number and magnet strength. It is observed that applying such magnetic field creates mixing in the flow and disturbance in the boundary layer development, leading to local enhancement in the convective heat transfer at regions close to the magnet position. Higher enhancement in heat transfer is observed when the ferrofluid with higher concentration and particle size is used. Using stronger magnets also improves the heat transfer rate, and the amount of enhancement is limited by the magnetic saturation phenomenon. Increasing the Reynolds number at a given magnet strength decreases the effectiveness of the applied magnetic field on the flow and heat transfer. To create more efficient mixing in the flow and disturbance in the boundary layer, four magnets at different positions are used. It is observed that the average convective heat transfer coefficient in case of using four magnets is about 40.79% and 58.19% higher than those of using no magnet with ferrofluid and pure water, respectively.

Combined Effects of Frictional and Joule Heating on MHD Nonlinear Radiative Casson and Williamson Ferrofluid Flows with Temperature Dependent Viscosity

The impacts of Joule’s dissipation and frictional heating on non-Newtonian ferrofluid flows past a bidirectionally stretching convective surface are investigated. We assumed that Fe3O4 nanoparticles are mixed with methanol. Both Casson and Williamson models are opted while formulating the basic flow equations. The impact of temperature dependent viscosity is accounted. The Joule heating and viscous dissipation impacts are also considered. Shooting and R.K. numerical procedures are used to solve the flow problem. Graphical and tabular illustrations are presented with a view of understanding the nature of flow and heat transfer for discrete values of flow parameters. It is worth to note that the thickness of velocity boundary layer of Casson fluid flow is greater than that of Williamson fluid flow. Also the presence of Joule and frictional heating leads to more heat energy to Casson fluid flow while compared to that of Williamson fluid. Heat transfer rate is better in Williamson fluid compared to that of Casson fluid.

Effect of Thermal Radiation on Heat Transfer of Ferrofluid Over a Stretching Cylinder with Convective Heating

In view of this we scrutinize the numerical solution using the Kellor box method for the natural differential equations which describes the MHD flow of ferrofluid over a stretching cylinder with thermal radiation and convective heating. Water as convectional base fluid containing nano particles of magnetite (Fe3O4) is taken up. Comparison between magnetite (Fe3O4) and non-magnatic (Al2O3) nanoparticles is also made. The relevant physical parameters appearing in velocity and temperature distributions are analyzed and examined with the help of Fig.s. To examine the correctness of the method an anology has been made with some earlier published results. It is noticed that by increase the strength of magnetic field, the percent difference in the heat transfer rate of magnetic nano particles with Al2O3 decrease. Further, convective heating and thermal radiation are highly influenced the temperature distribution of the ferrofluid.

A two-phase simulation for ferrofluid flow between two parallel plates under localized magnetic field by applying Lagrangian approach for nanoparticles

Abstract Hydrothermal characteristics of water–MnZnFe2O4 magnetic nanofluid between two parallel plates are evaluated under effect of localized magnetic field. The Eulerian–Lagrangian approach is employed considering the effects of Brownian, thermophoretic, magnetic, lift and drag forces. Convective heat transfer enhances by increasing each of the parameters of nanoparticle size, concentration and magnetic field strength. The rate of enhancement for convective heat transfer is lower at higher magnetic field strengths due to the magnetic saturation phenomenon. Concentration is non-uniform in transverse direction, and nanoparticles migrate to central regions. In the sections with positive magnetic field gradient, the magnetic force is exerted on the particles in the flow direction and consequently, velocity increases in the central regions while decreases near the walls. Conversely, in the sections where the magnetic field gradient is negative, the velocity decreases in the central regions while increases near the walls. This causes local changes in convective heat transfer. Moreover, the pressure increases along the channel in the sections with positive magnetic field gradient, whereas in the sections with negative magnetic field gradient, the pressure drops with a greater slope compared with the case without magnetic field. Additionally, the wall temperature decreases with increasing the magnetic field gradient.

A Comparative Study on the Ferrofluid Flow Models with Regards to the Behavior of A Ferrofluid Based Curved Rough Porous Circular Squeeze Film with Slip Velocity

This investigation plans to introduce a correlation among all the three magnetic fluid flow models (Neuringer-Rosensweig’s model, Shliomis’s model, Jenkins’s model) with regards to the conduct of a ferrofluid based curved rough porous circular squeeze film with slip velocity. The Beavers and Joseph's slip velocity has been invoked to assess the impact of slip velocity. Further, the stochastic model of Christensen and Tonder has been utilized to contemplate the impact of surface roughness. The load bearing capacity of the bearing system is found from the pressure distribution which is derived from the related stochastically averaged Reynolds type equation. The graphical portrayals guarantee that Shliomis model might be favoured for preparation of the bearing system with improved life period. However, for lower to moderate values of slip Neuringer-Rosensweig model might be considered. Morever, when the slip is at least the Jenkin's model might be deployed when the roughness is at reduced level.

Phase-field-based lattice Boltzmann model for multiphase ferrofluid flows

In this paper, we present a simple and accurate lattice Boltzmann (LB) model for immiscible two-phase flows, which is able to deal with large density contrasts. This model utilizes two LB equations, one of which is used to solve the conservative Allen-Cahn equation, and the other is adopted to solve the incompressible Navier-Stokes equations. A novel forcing distribution function is elaborately designed in the LB equation for the Navier-Stokes equations, which make it much simpler than the existing LB models. In addition, the proposed model can achieve superior numerical accuracy compared with previous Allen-Cahn type of LB models. Several benchmark two-phase problems, including static droplet, layered Poiseuille flow, and Spinodal decomposition are simulated to validate the present LB model. It is found that the present model can achieve relatively small spurious velocities in the LB community, and the obtained numerical results also show good agreement with the analytical solutions or some available results. At last, we use the present model to investigate the droplet impact on a thin liquid film with a large density ratio of 1000 and the Reynolds number ranging from 20 to 500. The fascinating phenomenon of droplet splashing is successfully reproduced by the present model and the numerically predicted spreading radius exhibits to obey the power law reported in the literature.

Stagnation Point Flow with Heat Transfer and Temporal Stability of Ferrofluid Past a Permeable Stretching/Shrinking Sheet

In this paper, the hydromagnetic stagnation point flow and temporal stability of Fe3O4-water ferrofluid over a convectively heated permeable stretching/shrinking sheet is theoretically investigated. The model equations of momentum and energy balance are obtained and transformed into ordinary differential equations using appropriate similarity variable. Using shooting method together with Runge-Kutta-Fehlberg numerical scheme the model nonlinear boundary value problem is tackled numerically. Pertinent results with respect to the basic steady flow velocity, temperature, skin friction and Nusselt number are obtained graphically and in tabular form. It is found that a critical value of shrinking parameter (λc) exists below which no real solution can be found. In addition, dual solutions (upper and lower branch) are observed for a range of shrinking/stretching parameter (λc<λ< 1), while for the stretching case (λ 1), the solution is unique. The obtained steady state solutions are examined for temporal development of small disturbances. The smallest eigenvalues reveal that the upper solution branch is stable and physically reliable while the lower solution branch is unstable and unrealistic. Both suction and magnetic field widen the range of the shrinking parameter for which the solution exists and boost the flow stability while nanoparticles volume fraction lessens it.

Numerical Simulation on the Induced Voltage Across the Coil Terminal by the Segmented Flow of Ferrofluid and Air-Layer.

Nanoparticles and nanofluids have been implemented in energy harvesting devices, and energy harvesting based on magnetic nanofluid flow was recently achieved by using a layer-built magnet and microbubble injection to induce a voltage on the order of 10-1 mV. However, this is not yet suitable for some commercial purpose. The air bubbles must be segmented in the base fluid, and the magnetic flux of the ferrofluids should change over time to increase the amount of electric voltage and current from energy harvesting. In this study, we proposed a novel technique to achieve segmented flow of the ferrofluids and the air layers. This segmented ferrofluid flow linear generator can increase the magnitude of the induced voltage from the energy harvesting system. In our experiments, a ferrofluid-filled capsule produced time-dependent changes in the magnetic flux through a multi-turn coil, and the induced voltage was generated on the order of about 101 mV at a low frequency of 2 Hz. A finite element analysis was used to describe the time-dependent change of the magnetic flux through the coil according to the motion of the segmented flow of the ferrofluid and the air-layer, and the induced voltage was generated to the order of 102 mV at a high frequency of 12.5 Hz.

Feasibility Study on a Segmented Ferrofluid Flow Linear Generator for Increasing the Time-Varying Magnetic Flux.

Nanoparticles and nanofluids have been implemented in energy harvesting devices, and energy harvesting based on magnetic nanofluid flow was recently achieved by using a layer-built magnet and micro-bubble injection to induce a voltage on the order of 10-1 mV. However, this is not yet suitable for some commercial purpose. In order to further increase the amount of electric voltage and current from this energy harvesting the air bubbles must be segmented in the base fluid, and the magnetic flux of the segmented flow should be materially altered over time. The focus of this research is on the development of a segmented ferrofluid flow linear generator that would scavenge electrical power from waste heat. Experiments were conducted to obtain the induced voltage, which was generated by moving a ferrofluid-filled capsule inside a multi-turn coil. Computations were then performed to explain the fundamental physical basis of the motion of the segmented flow of the ferrofluids and the air-layers.

Correction to: Simulation of ferrofluid flow boiling in helical tubes using two-fluid model

The family name of the fourth author should be Maroofiazar instead of Maroofi. The correct list of authors is shown above. The original article has been corrected.