Application of nanofluids: natural convection in cavities

The open literature contains an extensive study on the natural convection performance of nanofluids in different cavities subjected to diverse thermal conditions. Therefore, this study aims to present an updated review of published works in this regard with the focus on the level of convective heat transfer achieved owing to the use of different nanofluids, shapes of the cavity, base fluids, concentrations of nanoparticles, thermal conditions, controlling parameters (cavity inclination and aspect ratio, and magnetic field inclination), and enhancement techniques. Of huge contribution to this work is the effect of porous media, foams, baffles, partition, magnetic field, hybrid nanofluids, and heat conducting block as enhancement strategies on nanofluid convective heat transfer performance in cavities. In addition, a comparison is drawn between experimental and numerical studies on the hydrodynamics characteristics of nanofluids in enclosures. Studies on nanofluid bioconvection in cavities as a special case of natural convection heat transfer characteristics are also reviewed. Findings show the need to intensify experimental studies to adequately complement numerical works for better understanding as a wide gap is observed between the duo. Irrespective of the shapes of the cavity, nanofluid and base fluid types, thermal conditions, and controlling parameters, enhancement techniques are observed to unarguably augment/detract convective heat transfer. Inconsistencies are observed between and within numerical and experimental studies concerning the trend and nanoparticle concentration for improved natural convective thermal transport. The deployment of green base fluids and nanofluids, ionic liquids, and other novel materials to nanofluid natural convection research is highly recommended for future studies owing to health, environment, sustainability, and developmental issues.