Variations of MHD double-diffusive mixed convection and entropy generation in various nanofluids and hybrid nanofluids due to the deviation of the spinning of double rotating cylinders

Abstract

The current numerical study aims to investigate the effects of various rotating speeds of rotating cylinders on mixed convection and entropy generation in a lid-driven trapezoidal enclosure for fixed magnetic field inclination angle. Several water-based hybrid nanofluids are used as governing fluids. In this work, the impacts of SWCNT-water, Cu-water, and Al2O3-water nanofluids individually, as well as the effects of three different types of SWCNT-Cu-Al2O3-water hybrid nanofluids are examined. The average Nusselt number, average Sherwood number, average temperature, and average entropy generation because of heat transfer, diffusion, fluid friction, and the applied magnetic field as well as total entropy generation and Bejan number are evaluated as output parameters for different values of governing parameters. The Galerkin weighted residual finite element method is used to numerically solve the governing Navier-Stokes, thermal energy, and mass conservation equations. The optimal values of each governing parameter are established in order to produce the best results for the output parameters. To inspect the thermal and flow field within the trapezoidal enclosure as well as the variations in mass concentrations, isotherm contours, streamlines and isoconcentration contours are studied. Better performance is found for higher rotating speed regardless of other parameters.

Keywords

• Hybrid nanofluid
• Mixed convection
• Entropy
• MHD
• Double diffusive