Numerical Simulation Of Thermomagnetic Convection Of Air In A Porous Cubic Enclosure Under Gradient Magnetic Field

Strengthen or control of the convective heat transfer in porous medium is widely used in engineering practice. Using magnetic field to strengthen the convection heat transfer in porous media is the current hot research topic. However, most researchers focus more on the convection heat transfer of magnetic fluid or conductive fluid in porous media under gradient magnetic field. But the study of convection heat transfer of non conducting fluid in porous media under gradient magnetic field is involved little. In this paper, the thermomagnetic convection of air in a two-dimensional and three-dimensional porous square enclosure under a magnetic quadrupole field was numerically investigated. The following conclusions were obtained:(1) The results of numerical simulation of thermomagnetic convection of air in a porous cubic enclosure under loading current circular coil were showed follwing:In zero-gravity environment, When the coil is in a horizontal position (yeuler=0°),Due to the effect of magnetic force, which results in four cellular structures with horizontal symmetry about the middle plane of the enclosure.For yeuler=±90°, The cavity forming four cellular that tilt to the central level.The overall heat transfer is enhanced gradually with theincrease of yRa. The average Nusselt number is symmetrical with respect to the inclination angle at yeuler=0°.Under the gravity, the air that in the enclosure under the combined action of the magnetic buoyancy lift and the gravitational buoyancy lift.When the coil is in a horizontal position (yeuler=0°),large rolls are generated in the upper part of the cube and small convection rolls in the opposite direction are generated near the bottom floor.When yealer=±90°,due to the combined action of the magnetic buoyancy lift and the gravitational buoyancy lift. This produces a large clockwise vortex in the lower part of the enclosure and a small horizontal counter-clockwise rotating cell in level surface. When γ≥100. The average Nusselt number increases as the magnetic force number is increased., Num is increased and decreased alternately with the change of yeuler and Da.(2) The results of thermomagnetic convection of air in a two-dimensional porous square enclosure under a magnetic quadrupole field were showed follwing:In zero-gravity environment,two counter-clockwise rotating cells appear in the enclosure.low velocity increases with the increase of yRa, and take the space of the enclosure until be filled with the enclosure. Eventually, in the enclosure formed a thermal plume which isotherms on the top and bottom of the hot wall become dense and the area with dense isotherms on the cold wall moves from the top to the middle of the cold wall gradually. The results show that using magnetic fields to strengthen the convection heat transfer In the zero-gravity environment,In gravity environment, The results show that with the increase of the magnetic force number, the air flow in the porous enclosure presents a clockwise vortex at first and then appears the stratified phenomenon, which results in the formation of two vortexes with different rotational directions and intensities. Finally, the air flow in the enclosure is of two cellular structures with approximately horizontal symmetry about the middle of the enclosure. The change of the temperature field is similar to zero-gravity environment.