The laminar plume above a line heat source in a transverse magnetic field

The dynamics of a buoyant plume rising above a horizontal line heat source in a transverse, horizontal magnetic field is investigated. Similarity is shown to occur when the magnetic field strength varies as the −2/5 power of vertical distance from the source. The plume depends on two parameters — the Prandtl number (Pr) and the Lykoudis number (Z _L). Families of exact closed form solutions are derived for Pr=5/9 and Pr≥2. A family of numerical integrations for Pr=0.01 (typical of liquid metals) is also reported. The magnetic field is shown to affect the profiles of velocity and temperature by altering the similarity functions, the coefficients, and the value of the independent similarity variable corresponding to a fixed physical position. An approximate closed form solution valid for low Pr and high Z _L is presented. Possible experimental tests of the theory are proposed. Research sponsored by the U.S. Energy Research and Development Administration under interagency agreement with Union Carbide Corporation.     

Influence of a magnetic field on the thermoacoustic stability of a high-temperature heat releasing gas

The conditions of thermoacoustic stability are found for a high-temperature electrically conducting gas with internal heat release in a constant magnetic field which transforms acoustic waves into fast and slow magnetoacoustic oscillations, and also introduces Joule dissipation. The investigation is by means of the energy balance method, and also by direct solution of the equations for small perturbations in the special case of wavelengths of the acoustic oscillations that are short compared with the inhomogeneity scales in the region of heat release. The limits of stability with respect to fast and slow magnetoacoustic oscillations are found.Translated from Izvestiya Akademii Nauk SSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 102–107, July–August, 1979.     

Experimental investigation on heat transfer characteristics of magnetic fluid flow around a fine wire under the influence of an external magnetic field

Experimental investigation is conducted to get insight into convective heat transfer features of the aqueous magnetic fluid flow over a fine wire under the influence of an external magnetic field. The convective heat transfer coefficient of the aqueous magnetic fluid flow around the heated wire is measured in both the uniform magnetic field and the magnetic field gradient. The effects of the external magnetic field strength and its orientation on the thermal behaviors of the magnetic fluids are analyzed. The experimental results show that the external magnetic field is a vital factor that affects the convective heat transfer performances of the magnetic fluids and the control of heat transfer processes of a magnetic fluid flow can be possible by applying an external magnetic field.     

Effect of magnetic field on 3D flow and heat transfer during solidification from a melt

We present the effect of a magnetic field on three-dimensional fluid flow and heat transfer during solidification from a melt in a cubic enclosure. The walls of the enclosure are considered perfectly electrically conducting and the magnetic field is applied separately in three directions. The finite-volume method with enthalpy formulation is used to solve the mathematical model in the solid and liquid phases. The results obtained by our computer code are compared with the numerical and experimental data found in the literature. For Gr = 5 × 10⁵ and Ha = 0, 25, 50, 75, and 100 (where Gr and Ha are the Grashof and Hartmann numbers, respectively), the effects of magnetic field on flow and thermal fields, and on solid/liquid interface shape are presented and discussed. The interface is localized with and without magnetic field. The results show a strong dependence between the interface shape and the intensity and orientation of magnetic field. When the magnetic field is applied along the X-direction, the magnetic stability diagrams (V_max–Ha) and (Nu_avg–Ha) show the strongest stabilization of the flow field and heat transfer.     

Nanofluid flow and heat transfer due to a stretching cylinder in the presence of magnetic field

In this paper, flow and heat transfer of a nanofluid over a stretching cylinder in the presence of magnetic field has been investigated. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved numerically by the fourth order Runge–Kutta integration scheme featuring a shooting technique. Different types of nanoparticles as copper (Cu), silver (Ag), alumina (Al₂O₃) and titanium oxide (TiO₂) with water as their base fluid has been considered. The influence of significant parameters such as nanoparticle volume fraction, nanofluids type, magnetic parameter and Reynolds number on the flow and heat transfer characteristics is discussed. It was found that the Nusselt number increases as each of Reynolds number or nanoparticles volume fraction increase, but it decreases as magnetic parameter increase. Also it can be found that choosing copper (for small of magnetic parameter) and alumina (for large values of magnetic parameter) leads to the highest cooling performance for this problem.     

MHD boundary layer flow and heat transfer over a stretching sheet with induced magnetic field

In this paper, the problem of steady magnetohydrodynamic boundary layer flow and heat transfer of a viscous and electrically conducting fluid over a stretching sheet is studied. The effect of the induced magnetic field is taken into account. The transformed ordinary differential equations are solved numerically using the finite-difference scheme known as the Keller-box method. Numerical results are obtained for various values of the magnetic parameter, the reciprocal magnetic Prandtl number and the Prandtl number. The effects of these parameters on the flow and heat transfer characteristics are determined and discussed in detail. When the magnetic field is absent, the closed analytical results for the skin friction are compared with the exact numerical results. Also the numerical results for the heat flux from the stretching surface are compared with the results reported by other authors when the magnetic field is absent. It is found that very good agreement exists.     

Thermal convection in a cylindrical enclosure with intense internal heat generation in the presence of a longitudinal magnetic field

Steady convection in a gaseous medium with intense heat generation is considered without making use of the Boussinesq approximation. The effect on convection of the thermal boundary conditions at the walls of the enclosure is investigated, together with the influence of a longitudinal magnetic field which is effective when the medium is strongly heated and becomes electrically conducting.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.3, pp. 11–18, May–June, 1992.The authors are grateful to the participants in the G. A. Lyubimov seminar for discussing their work.     

A numerical study on heat transfer of a ferrofluid flow in a square cavity under simultaneous gravitational and magnetic convection

Theoretical and Computational Fluid Dynamics - Thermomagnetic convection is based on the use of external magnetic fields to better control heat transfer fluxes in ferrofluids, finding important...     

The experimental study on flat plate heat pipe of magnetic working fluid

An effective thermal spreader can achieve uniform heat flux distribution and thus enhance heat dissipation of heat sinks. Flat plate heat pipe is one of the highly effective thermal spreaders. Magnetic fluid is liquid and can be moved by the force of magnetic field. Therefore, the magnetic fluid is suitable to be used as the working fluid of flat plate heat pipes which have a very small gap between evaporation and condensation surfaces. We prepared a disk-shaped wickless flat plate heat pipe, and the distance between evaporation and condensation surfaces is only 1 mm. From experimental study, the effect of heat flux and working fluid ratio on the performance of flat plate heat pipe is presented. Also we compared the experimental results between the performance of water and magnetic fluid as working fluids.     

Yield stress of a magnetic fluid in a magnetic field

The yield stress ₀ of a magnetic fluid in a plane channel and the shape of the chains restraining the motion of the fluid are determined. The equilibrium problem for a magnetic fluid in a plane channel in the presence of an external magnetic field perpendicular to the plane of the channel and a pressure difference between the channel ends is solved within the framework of the structured fluid model. It is shown that equilibrium is possible only when the pressure difference does not exceed a certain limit p _cr at which the shear stress on the channel wall has a maximum. In weak fields p _cr and the corresponding ₀ depend quadratically on the field and in strong fields tend to saturation. The phenomenological parameters of the model are estimated for the case in which the microstructure is a system of chains of magnetic particles. The results obtained are found to be in qualitative agreement with the experimentally observed dependence of p _cr and ₀ on the field and the magnetic phase concentration.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.3, pp. 4–10, May–June, 1992.The authors are grateful to V. V. Gogosov for useful discussions and his interest in the work.     

Peristaltic transport of fourth grade fluid with heat transfer and induced magnetic field

We investigate the influence of an induced magnetic field on the peristaltic flow of an incompressible fourth grade fluid in a symmetric channel with heat transfer. Adopting long wavelength, low Reynolds number and small Deborah number assumptions we derive the solutions for stream function, pressure gradient, temperature, magnetic force function, induced magnetic field and current density. Qualitative agreement is demonstrated between the graphs and expected observations.     

Heat transfer in flow past a continuously moving semi-infinite flat plate in transverse magnetic field with heat flux

Thermal boundary layer on a continuously moving semi-infinite flat plate in the presence of transverse magnetic field with heat flux has been examined. Similarity solutions have been derived and the resulting equations are integrated numerically. This investigation has indicated a fall in the temperature of the thermal boundary layer with increase in magnetic field parameter.

---

Wärmeübertragung in Strömungen an einer gleichmäßig bewegten, halbunendlichen ebenen Platte in einem quergerichteten Magnetfeld mit Wärmefluß

Zusammenfassung Es ist die thermische Grenzschicht auf einer gleichmäßig bewegten, halbunendlichen ebenen Platte in einem quergerichteten Magnetfeld mit Wärmefluß untersucht worden. Ähnlichkeitslösungen sind abgeleitet und die erhaltenen Gleichungen numerisch integriert worden. Diese Untersuchung hat einen Rückgang der Temperatur in der thermischen Grenzschicht mit steigendem Magnetfeldparameter nachgewiesen.

     

Flow and heat exchange in a layer of a viscous conducting fluid between rotating plates with horizontal gradients of temperature in a transverse magnetic field

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 124–128, July–August, 1990.     

Importance of induced magnetic field and exponential heat source on convective flow of Casson fluid in a micro-channel via AGM

The study of the natural convective flow of a fluid in the presence of an induced magnetic field has always been of considerable importance due to its many applications in various areas of science, technology, and industry, such as the operation of magnetohydrodynamic generators. This study addresses an analysis of exponential heat source and induced magnetic field on the second-class convection of Casson fluid in a microchannel. The flow is in a vertical microchannel organized by two vertical plates. The answer to governing equations has been grabbed for temperature field, induced magnetic field, and velocity via Akbari-Ganji's method (AGM). Nusselt number, skin friction coefficient, and current density are approximated. Graphs that describe the conclusion of influential physical variables on velocity, temperature, current density, induced magnetic field, and skin friction coefficient distributions are shown. Comparison of results with numerical method (Runge-Kutta-Fehlberg, RKF-45), homotopy perturbation method, and AGM confirms the accuracy of answers obtained with AGM.     

Statics of a magnetic fluid containing magnetic field concentrators

Various static surface shapes of a magnetic fluid containing bodies made of easily magnetizable materials (magnetic field concentrators) in a uniform applied magnetic field are numerically calculated with account for the gravity force, surface tension, and the dependence of the magnetic-fluid magnetization on the magnetic field strength. The possibility of a sudden change in surface shape is shown. Hysteresis in the surface shape with a cyclic increase and decrease in the applied field is predicted.     

Analysis of the transient thermal field and heat flux in circular plates, heated rapidly by a fast-decaying magnetic field

The rapid heating of a circular conducting plate by a magnetic field decaying exponentially with time and its transition to a final steady-state is studied for the cases of both isolated and non-isolated plates. Analytic expressions are derived for the thermal field, the heat flux and the relaxation times. Both the ’‘thin” and the “thick” aspects of the problem are investigated. Emphasis is placed upon some characteristic parameters arising from the analytical solution. Attention is paid to the time constants, related to the combined (conduction and convection) thermal process. In fact, the ratio of these time constants determines the transition process up to the final steady-state of each region of the plate.     

Experiments and mechanism analysis of pool boiling heat transfer enhancement with water-based magnetic fluid

A pool boiling heat transfer comparison among water-based magnetic fluids in the absence and presence of a magnetic field with its carrier liquid water was made. The experimental results show that the boiling heat transfer of magnetic fluid increased much in the absence of a magnetic field, and the applied magnetic field made the boiling heat transfer of magnetic fluid enhance further. The effect of a magnetic field on bubbles was analyzed. It was clarified that the nonuniform magnetic field changed the bubble departure diameter and shape during boiling.