Natural convection of multi-walled carbon nanotube-Fe3O4/water magnetic hybrid nanofluid flowing in porous medium considering the impacts of magnetic field-dependent viscosity

摘要

The study ahead deals with the natural convection of MWCN-Fe3O4/water magnetic hybrid nanofluid flowing in a porous medium. The flow domain is affected by an inclined magnetic field influencing the dynamic viscosity. The dependency of the flow and heat transfer characteristics on Rayleigh number, Ra = 10(3)-10(6); Hartman number, Ha = 0-50; inclination angle of the magnetic field, phi = 0 degrees-180 degrees; magnetic number, delta(0) = 0-2.0; porosity, epsilon = 0.1-0.9; Darcy number, Da = 10(-7)-10(-1);and volume fraction of the composite nanoparticles, phi = 0, 0.1 and 0.3% is studied numerically. At low Rayleigh number Ra = 10(4), dispersing the nanocomposite particles increases the average Nusselt number Nu(avg), while that decreases the Nu(avg) when Ra = 10(5) and 10(6). The dependency of viscosity on the magnetic field decreases the Nu(avg) at 0 degrees < phi < 135 degrees, which is due to an increase in overall viscosity of the nanofluid. After that (phi >= 135 degrees), the average Nusselt number is greatly enhanced by increasing phi from 135 degrees up to 180 degrees. There is no meaningful change in average Nusselt number of the hybrid nanofluid by increasing the inclination angle of magnetic field in the absence of magnetic field-dependent viscosity (delta(0) = 0).