Analyse (CFD) de l’Ecoulement en Convection Forcée Turbulente autour des Chicanes Décalées dans un Canal Rectangulaire : Effet de Combinaison de Deux Chicanes (Plate et en Forme de V)

Abstract

This is a numerical investigation of the performance of a new obstacle design aiming to enhance the heat transfer phenomenon in a solar air channel. A combination of two transverse, solidtype obstacles of different shapes is used in this contribution; they are fixed to the top and bottom walls of the channel, in a periodically staggered manner in order to develop vortices to improve the mixing and consequently the heat transfer. The first obstacle to be introduced in the channel is the flat rectangular-shaped obstacle (called: simple fin); it is attached to the top hot surface, while the attack angle, height, position, and the shape of the second obstacle (called: baffle) is varied to identify the optimum configuration for enhanced heat transfer. This is an important problem in the scope of solar air collectors where the characterization of the fluid flow, heat transfer distribution, as well as the existence and the extension of possible recirculations need to be identified. Simulations are considered steady and the flow regime is turbulent. Air, whose Prandtl number (Pr) is 0.71, is the working fluid used, and the Reynolds numbers considered range from 12,000 to 32,000. The turbulent governing equations are solved by a finite volume method with the SIMPLE discretization algorithm and the k-epsilon turbulence model to describe the turbulent structure. The computational domain is validated through three distinct steps, namely grid independence, validation with the numerical and experimental results and verification with the smooth rectangular air channel. In particular, streamlines; mean, axial, and transverse velocity fields; fields of dynamic pressure, turbulent kinetic energy, turbulent intensity, turbulent viscosity, and temperature; dimensionless axial velocity profiles; normalized local and average Nusselt numbers; normalized local and average friction coefficients; and thermal enhancement factors are obtained at constant wall temperature condition along the top channel wall. The results of this thesis are of great significance in the optimal design of the solar air collectors.