Hybrid-nanofluid mixed convection in square cavity subjected to oriented magnetic field and multiple rotating rough cylinders

Abstract

In this study, mixed convective hybrid-nanofluid flow in a partially heated square cavity with two rotating rough cylinders in presence of an external magnetic field is numerically investigated. A pair of rotating rough cylinders is placed at different locations inside the cavity. The cavity is permeated by an external magnetic field at different inclination angles. Maxwell's thermal conductivity model is modified incorporating Brownian motion of hybrid nanoparticles. The conservation equations of the flow and thermal fields are simulated using finite element method. The effects of different influential parameters such as cylinders rotation velocity (0 ≤ ω ≤ 50), Hartmann number (0 ≤ Ha ≤50), hybrid nanoparticle volume fraction (0% ≤ φ ≤ 5%) and magnetic inclination angle (0° ≤ α ≤ 135°) on the flow and thermal fields are explored via streamlines, isotherms and bar charts of average Nusselt number. The simulated results ensure that mixed convective flow is accelerated with cylinders rotation speed but declines with higher magnetic field strength and hybrid-nanoparticle volume fraction. Heat transfer enhancement is recorded up to 261.29% at highest rotating speed of rough cylinders (ω: 0–50, φ = 1%, Ha = 10). Enhancement of heat transfer rate is found decreasing for increasing magnetic field strength. Lowest heat transfer rate is occurred at highest magnetic field impact (Ha = 50) which is 144.62% less than that of heat transfer in absence of magnetic field (Ha = 0). Optimum heat transfer is found for 5% hybrid nanoparticle volume fraction which is 101.2% more compared to base fluid water. The presence of triangular rough components accelerates the fluid flow and heat transfer rate significantly. In addition, 48.89% more heat transfer is obtained for rotating rough cylinders with triangular components compared to smooth cylinders. Moreover, maximum heat transfer is achieved at magnetic inclination angle of 90°. It is also observed that the flow and thermal fields strongly depend on the cylinders arrangements.