A numerical study of the effect of the magnetic field on turbulent fluid flow, heat transfer and entropy generation of hybrid nanofluid in a trapezoidal enclosure

.The purpose of this research is the numerical study of turbulent flow field, heat transfer and entropy generation of a Cuo-MWCNT-oil hybrid nanofluid in a trapezoidal enclosure under the influence of a magnetic field in natural convection. The enclosure side walls are insulated, the top wall is cold and the bottom one is hot. The study is done on Rayleigh numbers 10(7) to 10(10), Hartmann numbers 0 to 500, and volume fractions 0 to 1 percent of nanoparticles. The governing equations were solved numerically using a finite volume method and SIMPLER algorithm. According to numerical results, it was observed that the application and increase of a magnetic field increases the flow tendency to vortices. In all Rayleigh numbers and for all the studied Hartmann numbers, the stream function and average Nusselt number reduced by increasing the volume fraction of nanoparticles. It was also observed that for smaller Rayleigh numbers, increasing the Hartmann number will have a more tangible effect on reducing the average Nusselt number. By increasing the Rayleigh number in all the studied Hartmann numbers and volume fractions, the total entropy generated increased. The optimal mode for each Rayleigh number in terms of the minimum value of entropy generation is the least volume fraction and the most Hartmann number.