RAYLEIGH NUMBER EFFECT ON THE TURBULENT HEAT TRANSFER WITHIN A PARALLELEPIPED CAVITY

This purpose is about a 3-D study of natural convection within cavities. This problem is receiving more and more research interest dire to its practical applications in the engineering and the astrophysical research. The turbulent natural convection of air in an enclosed tall cavity with high aspect ratio (Ar = = H/W = 28.6) is examined numerically. Two cases of differential temperature have been considered between the lateral cavity plates corresponding, respectively, to the low and high Rayleigh numbers: Ra = 8.6.10(5) and Ra = = 1.43.10(6). For these two cases, the flow is characterized by a turbulent low Reynolds number. This led us to improve the flow characteristics using two one point closure low-Reynolds number turbulence models: renormalization group k-epsilon model and shear stress transport k-omega model, derived from standard k-epsilon model and standard k-omega model, respectively. Both turbulence models have provided an excellent agreement with the experimental data. In order to choose the best model, the average Nusselt number is compared to the experiment and other numerical results. The vorticity components surfaces confirm that the flow can be considered 2-D with stretched vortex in the cavity core. Finally, a correlation between Nusselt number and Rayleigh number is obtained to predict the heat transfer characteristics