LAUSR

Abstract Natural convection in a cavity with non-uniformly heated bottom wall, partly filled with a non-Newtonian nanofluid (Cu-water) layer and partly with air layer is studied numerically in this work. The mixture of water and copper nanoparticles shows a shear-thinning rheological behavior. The nanofluid's rheological parameters, i.e. consistency and flow index, are obtained according to the solid volume fraction, based on experimental data given in the literature. The general equations governing the physical problem are solved using the finite volume method over a wide range of Rayleigh number (103 ≤ Ra1 ≤ 106), volume fraction of nanoparticles (0% ≤ ϕ ≤ 5%), filling level of the lower phase (0.25 H ≤ Hnf ≤ H) and the aspect ratio of the cavity (0.5 ≤ A ≤ 4.0). The results show that both flow intensity and heat transfer are enhanced when increasing these parameters. Predictive correlations relating the average Nusselt number to the quoted parameters have been proposed.