Characterization of turbulent natural and mixed convection in confined enclosures equipped with a heat source

Abstract

In this numerical study two configurations are considered, the first configuration in natural convection corresponds to a closed cavity equipped with a heating bar and the second mixed configuration corresponds to the same cavity but ventilated. The flow is turbulent (Gr H = 1,2.10 8 ), a choice of model is very important. The turbulence model chosen for natural convection is the low-Reynolds k-e model. A comparison of the turbulence models led us to choose the RNG k-e model for mixed convection study, because it is the suitable model for flows in ventilated cavities as well as flows with recirculation. Ventilation effect on natural flow has been studied by analyzing flow dynamic and thermal structure. Nusselt average number on each bar face is found to be improved by jet injection into the ventilated cavity, from about 50% to 60%. This comparison reveals the different velocities influence of the incoming air jet on the confined cavity flow structure, or this jet succeeds in breaking the single-cell flow of natural convection case into a multicellular flow for the other case of mixed convection at high velocities above the heating bar, of which it is the main purpose of this study.