Role of entropy generation on thermal management of a porous solar collector using Al2O3-Cu/water nanofluid and magnetic field

The purpose of this study is a presentation of the thermal management of a flat plate solar collector via employing entropy generation analysis. The collector channel is completely saturated by porous metal foam locating in thermal non-equilibrium conditions. Al2O3-Cu/water hybrid nanofluid has been chosen in the role of working fluid, and considered flow has been assumed fully developed, hydrodynamically and thermally. The model of Darcy-Brinkman has been utilized to describe the hybrid nanofluid flow through the porous metal foam. Existing a magnetic field in the uniform state, its force affects the momentum equation. In addition, to characterize the temperature field of either phases of solid and fluid of the high porosity medium, two-equation model is utilized. Finally, the effect of key factors including porous media, volume fraction of hybrid nanofluid, and magnetic field on the total entropy generation and its components has been investigated. These results demonstrate that for weak magnetic field, when the base fluid's Reynolds number is less than 613, adding more nanoparticle to the base fluid would decrease the dimensionless average total irreversibility and a reverse trend is observed for the base fluid's Reynolds number. But, when the magnetic field is strong, for the Reynolds lower than 369.6, the dimensionless average total irreversibility is a decreasing function of nanofluid volume fraction and for Reynolds higher than 369.5, the trend would be reverse. In addition, due to the high-temperature gradient on the adsorption plate, a maximum local heat transfer irreversibility occurs on the adsorption plate. Also, due to the high velocity gradient on the solid walls of the collector channel, the maximum local fluid's friction irreversibility value is placed on the solid walls.