Magnetohydrodynamic natural convection of water-based SWCNT and MWCNT hybrid nanofluid inside a C-shaped cavity by varying aspect ratios

Abstract

This research article numerically investigates the natural convection and heat transfer analysis of water-based hybrid nanofluid composed of single-walled and multi-walled carbon nanotubes inside a C-shaped cavity under the magnetic field effect. The left vertical wall of the cavity is maintained at a uniform temperature T_h, whereas a specified portion of the right wall is kept at a constant temperature T_c. The remaining sections of the cavity boundaries are assumed to be thermally insulated. The study analyses the impact of parameters such as Rayleigh number (Ra = 10⁴ − 10⁷), the Hartmann number (Ha = 0 − 100), the volume fraction (ϕ_np = 1% - 4%) of the nanoparticles on the heat transfer and fluid fow within the enclosure. Additionally, the influence of aspect ratio variations (AR = 0.25 − 0.75) on heat transfer and fluid fow is analysed. The Galarkin's finite element method is used to solve the governing equations and the numerical solution is represented by plotting streamlines and isotherms. The results show that increasing the Rayleigh number strengthens convective motion, while higher Hartmann numbers suppress convection, causing heat transfer to be dominated by conduction. It is also notable that increasing the aspect ratio reduces the fluid flow rate due to limited space for rotation within the cavity, while smaller aspect ratios enhance thermal performance by promoting stronger fluid circulation.