ABSTRACT

Buoyancy driven natural convection in a nanofluid-filled square cavity induced by an arc-shaped heated baffle is analyzed numerically. Upper and bottom walls of the cavity are insulated and the remaining two walls have constant temperature; their values are lower than the baffle's temperature. The calculations were performed for various values of Rayleigh number (10⁴ « (Ra) « 10⁶) dimensionless arc length (0.25 « S « 0.75), shape parameter of the baffle (π/4 « Θ « π), types of nanoparticles (Cu, Al₂O₃) in a wide range of solid volume fraction of nanoparticles (0 « φ « 0.15). It is found that the net heat transfer can be enhanced by increasing the Rayleigh number, baffle length, and shape parameter. As the baffle length is increased for a fixed Rayleigh number, the average Nusselt number increases and for a fixed baffle length when the Rayleigh numbers are increased, the average Nusselt number also increases. The addition of copper and alumina Nanoparticles has produced a remarkable enhancement of the heat transfer. The average Nusselt number increases with increasing solid volume fraction of nanoparticles, especially at low Rayleigh numbers. Adding Al₂ O₃ increases the heat transfer rate but the influence of adding Cu nanoparticles to pure water on the heat transfer rate is much more pronounced because of its higher value of thermal conductivity compared to Al₂O₃. The difference in the average Nusselt number using different nanoparticles is negligible at low solid volume fractions, but as the volume fraction of nanoparticles increases, the difference for the mean Nusselt number becomes larger. This is similar to results which were obtained by other authors.