Numerical Simulation of the Turbulent Natural Convection in a Square Enclosure Filled with Water Based Al2O3 Nanofluids

A CFD simulation of the buoyancy—induced convection in a square enclosure filled with distilled water (DW) based Al2O3 nanofluids for Rayleigh number (Ra) range of 109–1012 is conducted. The enclosure is heated from below by applying constant heat flux condition and cooled from above by the constant temperature boundary condition, with the adiabatic condition at walls, which makes the test section a Rayleigh-Benard cavity. The particle size of 40 nm and particle concentration of 0.01 and 0.1 vol. % is used for Al2O3 nanoparticles. Results of the numerical work shown enhanced heat transfer at low concentration (0.01 vol. %) with the increase in Ra, while the opposite trend is observed for higher concentration (0.1 vol. %). The velocity of the fluid particles increased with the Ra and increased the turbulence in the test section. The eddy currents formed near the corners of the test section increased the resistance to the heat transfer, and the resistance further become strong with the Ra. A deterioration in the heat transfer occurred due to increased viscosity at higher Ra for both the concentrations of nanoparticles.