Abstract
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.
Highlights
The analysis of natural convection in enclosures has received increasing attention due to everyday practices and applications extending from the double paned windows in buildings to the cooling of electronic systems
Results revealed that the contribution of viscous effect on entropy generation cannot be ignored, while the contribution of mass transfer is negligible; the relative total entropy generation rates are nearly insensitive to the change of equivalence ratio; the order of the relative total entropy generation rates changes significantly depending on the inlet Reynolds number
Zone I is dominated by irreversibility due to chemical reaction, heat transfer and mass transfer while in Zone II it is predominated by irreversibility due to mass transfer and fluid friction
Summary
The analysis of natural convection in enclosures has received increasing attention due to everyday practices and applications extending from the double paned windows in buildings to the cooling of electronic systems. Valencia and Frederick [3] investigated the natural convection of air in square cavities with half-active and half-insulated vertical walls numerically for various Rayleigh numbers They observed that the heat transfer rates could be controlled, to a certain extent, by varying the relative positions of the hot and cold elements. Saravanan and Kandaswamy [4] analyzed the convection in a low Prandtl number fluid driven by the combined mechanism of buoyancy and surface tension in the presence of a uniform vertical magnetic field They showed that the heat transfer across the cavity from the hot wall to cold wall becomes poor for a decrease in thermal conductivity in the presence of a vertical magnetic field. They found that heat transfer rate increases with increase in the aspect ratio and when the cooling location is at the top of the enclosure
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