Natural convection of nanofluids in enclosures heated laterally and underneath

A two-phase mixture model is used to study natural convection in a square cavity filled with CuO+H2O nanofluids, in the hypothesis of temperature-dependent physical properties, assuming that Brownian diffusion and thermophoresis are the primary slip mechanisms between solid and liquid phases. The cavity is heated at one side and cooled at the opposite side, whereas the horizontal walls are assumed either both adiabatic, or the bottom heated and the top cooled. A computational code based on the SIMPLE-C algorithm is used to solve the system of the mass, momentum and energy transfer governing equations. It is found that, owing to the effects of the slip motion occurring between solid and liquid phases, the rate of heat transferred across the cavity by the nanofluid in the heating-from-below configuration is remarkably higher than that transferred by the pure base liquid. Moreover, in this particular configuration the addition of nanoparticles to the base liquid generates periodicity in heat transfer. Additionally, the heat transfer enhancement is discovered to increase as the imposed temperature difference is increased, showing a smooth maximum at an optimal particle loading.