NUMERICAL SIMULATION OF NATURAL CONVECTION IN RECTANGULAR CAVITIES WITH DIFFERENT ASPECT RATIOS

The problem of natural convection in rectangular cavities with different aspect ratios has been numerically analyzed in this study. Cavities considered have their right vertical walls heated and cooled at the opposite with constant temperatures, while horizontal walls are kept adiabatic. The objective of this study is to ascertain the significant effects of Rayleigh numbers (Ra), Nusselt numbers (Nu) and aspect ratios (AR) on flow and heat transfer in rectangular cavities. The equations of Navier-Stokes and energy are solved by applying Galerkin weighted residual Finite Element Method. Parametric calculations are performed for Rayleigh numbers (Ra) ranging from 104 to 108 and for aspect ratios (AR=0.25, 0.5, 1 and 2). Variations of Streamlines and Isotherms contours of the resulting flow fields and temperatures are presented in correlation with the estimated Nusselt numbers (Nu) for a fluid measured at air room temperature having Prandtl number (Pr) of 0.71. The results of the numerical simulation reveals that at higher Rayleigh number of flow, heat transfer in rectangular cavities increases. The Nusselt number estimated close to the boundary of the hot wall indicate a predominant heat transfer by convection in higher AR, hence, results indicates that with increasing aspect ratio, the thermal boundary layer thickness were steadily increased thereby contributing to major heat transfer of fluid by convection in the rectangular cavities. The engineering application of natural convection in cavities such as thermal storage facilities has made this study significant.