Computer simulations of natural convection of single phase nanofluids in simple enclosures: A critical review

The objective of the present work is to show that the internal natural convection of single phase nanofluids in enclosures can be easily predicted theoretically with no need to perform a numerical simulation provided that a reliable Nusselt number correlation for clear fluids in these enclosures is available. Six common enclosures shapes for which nanofluid heat transfer has been the subject of investigation in recent publications are selected for the present study. Computer simulations are performed to find the Nusselt number and the heat transfer coefficient for natural convection of nanofluids in horizontal and tilted square, horizontal and vertical annulus, triangular enclosure and the Rayleigh-Bénard convection configuration. The results of numerical simulations are compared with the prediction of a theoretical approach which uses the Nusselt correlations available in the literature for clear fluids. This comparison clearly shows that most of the earlier single phase numerical simulations for natural convection of nanofluids in cavities are redundant and the same predictions could be obtained theoretically in a much simpler way. The study was performed for Al2O3 and CuO nanofluids. In addition, critical reviews of recent publications on numerical simulation of natural convection of single phase nanofluids are presented.

► Numerical single phase modeling for the cases with available correlations is redundant.
► Available correlations for clear fluids can predict the natural convection of nanofluids.
► Nusselt number is a linearly decreasing function of φ in the range of φ < 0.06 and Ra < 106.
► (φ)at which heat transfer is maximum = f(Enclosure Shape, Type of nanofluid, Ra, Tav, dp).