Numerical investigation of turbulent natural convection in a round bottom flask using a hybrid nanofluid

Abstract In this study, we conducted a numerical investigation of the turbulent natural convection of a hybrid nanofluid (HNF) in a flask equipped with an agitator, which is commonly used in organic chemistry synthesis. The bottom wall and the middle section of the flask were maintained at a constant high temperature Th, while the upper, left, and right walls up to the middle of the flask were kept at a low temperature Tc. The HNF consisted of Graphene (Gr) and Carbon nanotube (CNT) nanoparticles (NP) dispersed in pure water. The governing equations were solved numerically using the finite size approach and formulated using the Boussinesq approximation. The effects of the NP volume fraction 𝜑 (ranging from 0–6%), the Rayleigh number Ra (ranging from 104 to 106), and the Nusselt number were investigated in this simulation. The results indicated that the heat transfer is noticeably influenced by the Ra number and the increase in the 𝜑 ratio. Additionally, the agitator rotation speed had a slight effect on the heat transfer.