Etude numérique de la convection mixte turbulente application à la ventilation des cavités chauffées.

Abstract

This work presents a two-dimensional numerical study of the phenomena of mixed laminar and turbulent convection in a ventilated square cavity. The geometry considered consists of three blocks dissipating heat by Joule effect at a constant temperature generated by an electric current arranged on the right vertical wall. All other parts of the cavity walls are considered adiabatic. The objective of this thesis is to characterize the best conditions to ensure a more efficient cooling of the cavity. This thesis work is divided into two main parts. The first part deals with mixed convection in laminar regime. This part is modeled by the current function, vorticity and energy equations, and discretized by the finite difference method. The resulting system of equations is solved by the line-by-line scanning method based on the Thomas algorithm (TDMA) by running a computational program developed in FORTRAN language. The second and most important one concerns a parametric study of the turbulent mixed convection. The equations of the considered mathematical model are established and discretized by the finite volume method under the commercial numerical calculation code FLUENT. The turbulence standard k-ε model is chosen to model the Reynolds constraints and the Simple algorithm is used to overcome the velocity - pressure coupling. After validation of the numerical codes with published experimental results, several numerical investigations were carried out to study the effect of: heat source arrangements inside the cavity, the location of fluid entry and exit, the Prandtl number and the Richardson number on the thermal and dynamic fields. The results concerning the flow fields, the thermal field as well as the Nusselt number were presented and discussed for both laminar and turbulent regimes. Analysis of the results obtained highlights the various conditions for better heat removal from the interior of the cavity.