Effect of the magnetic field on the ferrofluid flow in a curved cylindrical annular duct
TL;DR: In this paper, the effect of the magnetic field on the ferrofluid flow was analyzed in the toroidal-poloidal coordinate system and the results confirmed the ability of the method to produce accurate results in curvilinear coordinates and stretched grids.
Abstract: The laminar fully developed ferrofluid flow of an otherwise magnetic fluid into a curved annular duct of circular cross section, subjected to a transverse external magnetic field, is studied in the present work. The specific geometry is chosen as it is encountered in heat exchangers and mixers where compactness is a priority. Results are obtained for different values of curvature, field strength, and particles’ volumetric concentration. A computational algorithm is used which couples the continuity, Navier Stokes, and magnetization equations using a nonuniform grid. The velocity–pressure coupling is achieved using the so-called continuity-vorticity-pressure variational equation method, adapted to the toroidal-poloidal coordinate system. The results confirm the ability of the method to produce accurate results in curvilinear coordinates and stretched grids, which is important for the standardization of the method’s application to generalized coordinate systems. Concerning the micropolar flow characteristics, the results reveal the effect of the magnetic field on the ferrofluid flow. It is shown that the axial velocity distribution is highly affected by the field strength and the volumetric concentration, that the axial pressure drop depends almost linearly on the field strength, and that a secondary flow is generated due to the combined effect of the external magnetic field and the curvature. The present analysis provides important insight into the effect of the three main parameters, revealing cases where a straight annular pipe might be preferable to a curved one and specific parts of the pipe that could be susceptible to enhanced loads, giving information that is crucial for design optimization.The laminar fully developed ferrofluid flow of an otherwise magnetic fluid into a curved annular duct of circular cross section, subjected to a transverse external magnetic field, is studied in the present work. The specific geometry is chosen as it is encountered in heat exchangers and mixers where compactness is a priority. Results are obtained for different values of curvature, field strength, and particles’ volumetric concentration. A computational algorithm is used which couples the continuity, Navier Stokes, and magnetization equations using a nonuniform grid. The velocity–pressure coupling is achieved using the so-called continuity-vorticity-pressure variational equation method, adapted to the toroidal-poloidal coordinate system. The results confirm the ability of the method to produce accurate results in curvilinear coordinates and stretched grids, which is important for the standardization of the method’s application to generalized coordinate systems. Concerning the micropolar flow characteristic...
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TL;DR: In this article, the effect of a non-uniform magnetic field on the ferrofluid flow pattern, heat transfer and entropy generation in a curved pipe was investigated. But the authors focused on the application of the magnetic field in the case of finite volume.
Abstract: This paper presents the effect of a magnetic field on the ferrofluid flow pattern, heat transfer and entropy generation in a curved pipe. A non-uniform magnetic field is applied to ferrofluid (water + 2% vol. Fe3O4 nanoparticles) flow and under the constant heat flux boundary condition. Governing equations are solved by the finite volume method and based on the SIMPLE algorithm. The major objective of this work is to illustrate the effects of circumferential angle $$\left( {0^\circ \le \phi \le 180^\circ } \right)$$ and strengths of a magnetic field $$\left( {0 \le {\text{Mn}} \le 3 \times 10^{6} } \right)$$ on the hydro-thermal behavior and entropy production rate. It is found that circumferential angle of the magnetic source plays an important role in hydro-thermal performance of a curved pipe. At low magnetic numbers, the optimal circumferential location of the magnetic source is $$\phi_{\text{opt}} = 180^\circ$$ which leads to the maximum heat transfer enhancement and hydro-thermal performance and the minimal entropy generation rate. For high magnetic numbers, the optimal operating condition occurs at $$\phi = 0^\circ$$ and $$\phi = 60^\circ$$ depending on the magnetic number. Second law analysis reveals that the major source of entropy generation comes from heat transfer irreversibility which reduces significantly by applying a magnetic field. In the range of studied parameters, the maximum heat transfer enhancement is about 29% which occurs at $$\phi = 0^\circ$$ and $${\text{Mn}} = 3 \times 10^{6}$$.
14 citations
TL;DR: In this article, a numerical analysis of heat transfer and flow characteristics of a ferrofluid inside an annulus is presented, where the inner tube is heated uniformly while the outer tube is insulated.
9 citations
TL;DR: In this paper , the effect of applying various magnetic field intensity 15.1, 30.3, 45.5 mT on heat transfer enhancement in a horizontal pipe heated with constant heating flux of 420
Abstract: Different volume concentrations (1.2, 0.6, 0.3 wt%) of Fe3O4/water nanofluids and for different Reynolds number (Re) varying from 2180 to 9160 were used experimentally. The aim of work is to study the effect of applying various magnetic field intensity 15.1, 30.3, 45.5 mT on heat transfer enhancement in a horizontal pipe heated with constant heating flux of 420 W. Results showed that Nusselt number (Nu) increases with increasing Re for the nanofluids and water regardless the presence or absence of the magnetic field. Also, higher values were obtained than water. The average increase in Nu for Fe3O4-nanofluids is 16.7% relative to water when the magnetic field is not applied. However, the average increase in heat transfer coefficient and Nusselt number are 9.4%, 26.1%, 31.3% and 8.8%, 13.1%, and 23.9% in the presence of magnetic field ( Φ = 15 . 5 , 30 . 3 , 45 . 5 ) mT compared to the absence of magnetic field and base fluid water, respectively. Furthermore, pressure drop increases with the increase of Reynolds number and magnetic field strength. It can be concluded that the magnetic field has a big effect on the thermal transfer performance of Fe3O4/water nanofluid when compared with the thermal motion of magnetic nanoparticles. Finally, it is found that the performance factor is above unity in the presence and absence of magnetic field strength. This means that Nusselt number enhancement is higher than friction changes, which indicates the applicability of the heated pipe in the improvement of heat transfer. These results can be useful for enhancing heat transfer in many engineering applications such as heat exchangers, medical devices, and electronic devices.
4 citations
TL;DR: In this article , a finite volume method based numerical study is performed to investigate the ferrofluid behavior in the laminar flow regime using the complete set of Ferrohydrodynamics equations.
4 citations
TL;DR: In this paper, the authors studied the laminar fully developed ferrofluid flow and heat transfer phenomena of an otherwise magnetic fluid into a vertical annular duct of circular crosssection and uniform temperatures on walls which were subjected to a transverse external magnetic field.
Abstract: 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.
3 citations
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TL;DR: The first experimental evidence of a ``negative-viscosity'' effect in a magnetic fluid is presented here and the theory developed here corroborates the experimental results.
Abstract: The first experimental evidence of a ``negative-viscosity'' effect in a magnetic fluid is presented here. In a Poiseuille flow, a constant magnetic field balances vorticity and impedes the rotation of individual magnetic particles. Conversely, an alternating magnetic field helps vorticity and favors this rotation: The magnetic energy is partially transformed into the angular momentum of the particles, which in turn is converted into a hydrodynamic motion of the fluid. It manifests itself in a decrease of the total viscosity: Its rotational part becomes negative. The theory developed here corroborates the experimental results.
191 citations
TL;DR: In this paper, the improvement of nanofluid heat transfer inside a porous cavity by means of a non-equilibrium model in the existence of Lorentz forces has been investigated by employing control volume based finite element method.
Abstract: In the present article, the improvement of nanofluid heat transfer inside a porous cavity by means of a non-equilibrium model in the existence of Lorentz forces has been investigated by employing control volume based finite element method Nanofluid properties are estimated by means of Koo-Kleinstreuer-Li The Darcy-Boussinesq approximation is utilized for the nanofluid flow Roles of the solid-nanofluid interface heat transfer parameter Nhs, Hartmann number Ha, porosity e, and Rayleigh number Ra were presented Outputs demonstrate that the convective flow decreases with the rise of Nhs, but it enhances with the rise of Ra Porosity has opposite relationship with the temperature gradient
165 citations
TL;DR: In this article, an experimental investigation on forced convection heat transfer of an aqueous ferrofluid flow passing through a circular copper tube in the presence of an alternating magnetic field was presented.
142 citations
TL;DR: In this paper, the impacts of a periodic magnetic field on natural convection and entropy generation of Fe3O4-water nanofluid flowing in a square enclosure were investigated.
123 citations
TL;DR: In this paper, the performance of water-based Mn-Zn ferrite magnetic nanofluid in a counter-flow double-pipe heat exchanger under quadrupole magnetic field using the two-phase Euler-Lagrange method was investigated.
121 citations