Analysis of the Magnetic Field Effect on Entropy Generation at Thermosolutal Convection in a Square Cavity (original) (raw)
Related papers
2011
Thermosolutal convection in a square cavity filled with air and submitted to an inclined magnetic field is investigated numerically. The cavity is heated and cooled along the active walls with a mass gradient whereas the two other walls of the cavity are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined in transient state for laminar flow by solving numerically the continuity, momentum energy and mass balance equations, using a Control Volume Finite-Element Method. The structure of the studied flows depends on four dimensionless parameters which are the Grashof number, the buoyancy ratio, the Hartman number and the inclination angle. The results show that the magnetic field parameter has a retarding effect on the flow in the cavity and this lead to a decrease of entropy generation, Temperature and concentration decrease with increasing value of the magnetic field parameter.
2009
This paper investigates the effect of an imposed magnetic field on the flow patterns, and the entropy generation in a square cavity. A control volume finite element method is used to solve the conservation equations at Prandtl number of 0.71. The effects of Grashof number, Hartmann number and inclination angle of the magnetic field are investigated. The study covers the range of the Hartmann number from 0 to 50, the magnetic field inclination angle from 0° to 90° with Grashof number ranging between 10^3 and 10^5. The effects of Hartmann number and the magnetic field inclination angle are presented graphically in terms of isotherm and streamline plots. The effect of the magnetic field is found to suppress the convection currents and heat transfer inside the cavity. This effect is significant for high Grashof numbers. Results show that the Nusselt number is clearly affected by the magnetic field. The effect of the Hartmann number on entropy generation was investigated in steady-unstea...
2011
Natural and thermosolutal convections in a confined cavity filled with air is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls of the cavity are adiabatic and insulated. Entropy generation due heat and mass transfers, fluid friction and magnetic effect has been determined in transient state laminar flow by solving numerically: the continuity, momentum and energy equations, using a Control Volume Finite Element Method. The structure of the studied flows depends on six dimensionless parameters which are: the thermal Grashof number, the inclination angle, the irreversibility distribution ratio and the aspect ratio of the cavity. In the presence of a magnetic and radiative effects, two others dimensionless parameters are used which are Hartmann number and Radiation parameter. The obtained results show that entropy generation tends towards asymptotic values for lower thermal Grashof number values, whereas it takes an oscillative...
Effect of an External Oriented Magnetic Field on Entropy Generation in Natural Convection
Entropy, 2010
The influence of an external oriented magnetic field on entropy generation in natural convection for air and liquid gallium is numerically studied in steady-unsteady states by solving the mass, the momentum and the energy conservation equations. Entropy generation depends on five parameters which are: the Prandtl number, the irreversibility coefficients, the inclination angle of the magnetic field, the thermal Grashof and the Hartmann numbers. Effects of these parameters on total and local irreversibilities as well as on heat transfer and fluid flow are studied. It was found that the magnetic field tends to decrease the convection currents, the heat transfer and entropy generation inside the enclosure. Influence of inclination angle of the magnetic field on local irreversibility is then studied.
Entropy Generation in Heat and Mass Transfer in Porous Cavity Subjected to a Magnetic Field
2012
Numerical investigation is carried out to predict the entropy generation for combined natural convection heat and mass transfer in a two dimensional porous cavity subjected to a magnetic field. The Darcy model is used in the mathematical formulation of the flow in porous media. The mathematical model is derived in dimensionless form. The governing parameters arise in the mathematical model are the Rayleigh number, Lewis number, buoyancy ratio and Hartmann number. The entropy generation is obtained as a function of velocity, temperature, concentration gradients and the physical properties of the fluid. The results are presented as average Nusselt number, Sherwood numbers and dimensionless form of local entropy generation rate for different values of the governing parameters.The numerical results show that increasing the magnetic field parameter (Hartmann number) leads to reduce the flow circulation strength in the cavity and this leads to a decrease in the rate of entropy generation.
Journal of Applied Fluid Mechanics, 2016
In this study natural convection heat transfer fluid flow and entropy generation in a porous inclined cavity in the presence of uniform magnetic field is studied numerically. For control of heat transfer and entropy generation, one or two partitions are attached to horizontal walls. The left wall of enclosure is heated with a sinusoidal function and right wall is cooled isothermally. Horizontal walls of the enclosure are adiabatic. The governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique. The influence of Hartmann number, inclination angle, partition height, irreversibility distribution ratio, and partition location is investigated on the flow and heat transfer characteristics and the entropy generation. The obtained results indicated that the partition, magnetic field and rotation of enclosure can be used as control elements for heat transfer, fluid flow and entropy generation in porous medium.
The present study is devoted to the problem of onset of oscillatory instability in convective flow of an electrically conducting fluid under an externally imposed time-independent uniform magnetic field. Convection of a low-Prandtl-number fluid in a laterally heated two-dimensional horizontal cavity is considered. Fixed values of the aspect ratio ͑length/heightϭ4͒ and Prandtl number ͑Prϭ0.015͒, which are associated with the horizontal Bridgman crystal growth process and are commonly used for benchmarking purposes, are considered. The effect of a uniform magnetic field with different magnitudes and orientations on the stability of the two distinct branches ͑with a single-cell or a two-cell pattern͒ of the steady state flows is investigated. Stability diagrams showing the dependence of the critical Grashof number on the Hartmann number are presented. It is shown that a vertical magnetic field provides the strongest stabilization effect, and also that multiplicity of steady states is suppressed by the electromagnetic effect, so that at a certain field level only the single-cell flows remain stable. An analysis of the most dangerous flow perturbations shows that starting with a certain value of the Hartmann number, single-cell flows are destabilized inside thin Hartmann boundary layers. This can lead to destabilization of the flow with an increase of the field magnitude, as is seen from the stability diagrams obtained. Contrary to the expected monotonicity of the stabilization process with an increase of the field strength, the marginal stability curves show nonmonotonic behavior and may contain hysteresis loops.