Buoyancy-driven convection of MWCNT – Casson nanofluid in a wavy enclosure with a circular barrier and parallel hot/cold fins

A numerical interpretation is dedicated to analyse the flow and thermal characteristics of multiwall carbon nanotube (MWCNT) - sodium alginate (SA) Casson nanofluid in a complex wavy enclosure. The enclosure is designed with an insulated circular barrier under buoyancy effects. Two parallel fins are installed inside the complex enclosure in which one of the fins is assumed as hot and another one as cold. The enclosure is heated/insulated by the bottom/top wall. Forth-mentioned, geometry with nanofluid is mathematically modelled using partial differential equations with appropriate thermal and velocity boundary conditions. A parametric numerical examination is carried out via Galerkin finite element method for the key parameters such as Rayleigh number (10⁵<Ra_E<10⁷), Casson parameter (0.01<γ<1), solid volume fraction of MWCNT (0.02<φ<0.06), distance between the hot and cold fins (0.5<d<0.9) and the amplitude of the waviness (0.05<A<0.15). The flow and thermal efficiency are studied through stream function, isotherms, and dimensionless velocities, local and averaged Nusselt numbers graphs. It is found that the amplitude of the waviness, the distance between the fins, Casson parameter and Rayleigh number are the influential parameters on the flow and thermal patterns. The increased value of Rayleigh number, Casson parameter, solid volume fraction of MWCNT and amplitude of waviness enhanced the heat transfer rate by 257%, 189%, 30% and 116% respectively. Higher heat transfer rate is achieved when d =0.5. Furthermore, a new Nusselt number correlation is derived and presented.