Modeling and Measurements of Heat Transfer Phenomena in Two-Phase PbSn Alloy Solidification in an External Magnetic Field

The main aim of this work is to study numerically the influence of an external magnetic field on the solidification processes of two-component materials. Based on the continuum model of two-phase flow a mathematical model for the directional solidification of a binary alloy in a magnetic field is presented. The model includes mass, momentum, energy and species mass conservation equations written in compressible form and additional relationships describing the temperature-solute coupling. The geometry under study is a cylindrical mold with adiabatic walls and cooled bottom. The macroscale transport in the solidification of alloys is governed by the progress of the two-phase mushy zone, which is treated by means of a porous medium approach. The volume fraction of liquid and solid phases, respectively, is calculated from a 2D approximation of the phase diagram. The results of calculation are compared with experimental data.     

Flow characteristics of gallium in a meso-scale channel under the influence of magnetic fields

Flow characteristics of the liquid metal (gallium) in a meso-scale channel under the influence of a magnetic field, are investigated numerically. Low Reynolds number flow is considered. Runs with a magnetic field that has different orientations relative to the main flow direction in the channel are conducted. The impact of the induced Lorentz force acting on the flow field is quantified. The channel in which the flow takes place has a maximum width of 2 mm and a total length of 8 mm. The study represents a precursor for future investigations that target enhancing heat transfer performance in small scale channels, that might be of importance for example in electronic cooling applications. The results show that different magnetic field orientations lead to significant changes in the flow field. The results also highlight the need for further such investigations to explore further the effect of the applied magnetic fields under different flow rates, different channel geometry, and different channel size conditions.     

A novel magnetic separation oxygen-enriched method and the influence of temperature and magnetic field on enrichment

A novel oxygen-enriched method is presented.Using two opposite magnetic poles of two magnets with certaindistance forms a magnetic space having a field intensity gradient near its borders.When air injected into themagnetic space outflows from the magnetic space via its borders,oxygen molecules in air will experience the in-terception effect of the gradient magnetic field,but nitrogen molecules will outflow without hindrance.Therebythe continuous oxygen enrichment is realized.The results show that the maximum increment of oxygen concen-tration reaches 0.49% at 298 K when the maximum product of magnetic flux density and field intensity gradientis 563T~2/m.The enrichment level is significantly influenced by the gas temperature and the magnetic field.Themaximum increment of oxygen concentration drops to 0.16% when the gas temperature rises to 343 K,and dropsto 0.09% when the maximum product of magnetic flux density and gradient is reduced to 101 T~2/m from 563T~2/m.     

Effect of static magnetic field on a thermal conductivity measurement of a molten droplet using an electromagnetic levitation technique

Recently, a novel method of measuring the thermophysical properties, particularly thermal conductivity, of high-temperature molten materials using the electromagnetic levitation technique has been developed by Kobatake et al. [H. Kobatake, H. Fukuyama, I. Minato, T. Tsukada, S. Awaji, Noncontact measurement of thermal conductivity of liquid silicon in a static magnetic field, Appl. Phys. Lett. 90 (2007) 094102]; this method is based on a periodic laser-heating method, and entails the superimposing of a static magnetic field to suppress convection in an electromagnetically levitated droplet. In this work, to confirm the fact that a static magnetic field really suppresses convection in a molten silicon droplet in an electromagnetic levitator, numerical simulations of convection in the droplet and periodic laser heating in the presence of convection have been carried out. Here, the convections driven by buoyancy force, thermocapillary force due to the temperature dependence of the surface tension on the melt surface, and electromagnetic force in the droplet were considered. As a result, it was found that applying a static magnetic field of 4 T can suppress convection in a molten silicon droplet enough to measure the real thermal conductivity of molten silicon.     

Studying the effect of the force convection boundary condition and radius magnetic field on fluid flow and heat transfer between coaxial pipes

An investigation of the heat transfer of Newtonian fluid flow through coaxial two pipes with variable radius ratio has been conducted with the boundary conditions of forced convection on the inner pipe walls and a radius magnetic field. This paper presents an exact analytical solution to the momentum equation and a novel semi-analytic collocation method for solving the full-term energy equation that takes Joule heating into account as well as viscous dissipation. Based on the results of the numerical fourth-order Runge–Kutta method, it was found that increasing the magnetic parameter decreased the amount of friction on the surface of the pipe walls and the rate of heat transfer. As the radius ratio of the two pipes increases, so does the skin friction and heat transfer rate on the internal pipe walls. As Eckert (Ec) and Prandtl (Pr) numbers increase, the mean temperature as well as the dimensionless temperature between the two pipes increases. The increase in Biot number (Bi) has the opposite impact on the mean temperature. As Ec, Pr, and Bi increase, so does the rate of heat transfer on the inner wall of the pipe.     

Modify homotopy perturbation method using yang transform to study the effect of magnetic field with mass and heat transfer on pulsatile blood flow in tapered stenosis arteries

The effect of a magnetic field on two-dimensional pulsatile blood flow in tapered stenosis arteries was studied by employing the Yang transform homotopy perturbation method (YTHPM). The mathematical model which was solved by the researchers Liu and Liu, was successfully developed by adding the effect of a magnetic field for the blood flow in addition to the effect of mass and heat transfer on it. The impact of the angle of tapering, the Grashof number, the solutal Grashof number, and the magnetic field on the axial velocity, the wall shear stress, flow resistance, and the volumetric flow rate was investigated in two cases absence and presence of the magnetic field. The results prove that YTHPM is efficacious and highly accurate in finding the analytical approximate solution for pulsatile blood flow in tapered stenosis arteries under the influence of a magnetic field. The convergence of the new solutions is also discussed in the absence and presence of the magnetic field. Further, the graphs of these new solutions show the validity of, a necessity for, and utility of YTHPM, and are in line with results put forward by other studies.     

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

This 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.