Modelling Of Roughness Effect On Laminar Flow And Heat Transfer In Rectangular Microchannels
Résumé
The present paper is devoted to the numerical modeling of roughness effects on laminar flow in microchannels. 3D numerical simulations were initially performed and, based on their solutions, a roughness model is proposed. This one-dimensional model is inspired by a discrete-element approach due to Taylor et al. (1985, 1989). In this model, the channel consists in a clear medium adjacent to a porous medium layer where the interactions between the stream and the roughness elements are directly computed by the discrete-element method. Empirical correlations based on 2D numerical simulations of cross-flow through a bank of rods are used for modeling the local drag coefficient and the local Nusselt number of the roughness elements. The appropriate determination of these important parameters allows solving the momentum and energy equations in order to obtain the velocity and temperature profiles. The 1D model solutions are then compared with the 3D numerical solutions showing a very good agreement. The present study shows that roughness significantly influences both the Poiseuille number and the global Nusselt number. The relative increase of the pressure drop is found to be much faster than that of the heat transfer coefficient when the roughness height is increased. Two microchannels were produced with the same three-dimensional roughness arrangement as in the 3D numerical model and experiments were performed with deionized water as the working fluid. The height of microchannels was 106 μm and 153 μm with relative roughness of 16% and 14% respectively. Comparison between experiments conducted in isothermal conditions and model solutions shows the good ability of the numerical models to predict the pressure drop in the rough microchannels, which were tested.
Origine : Fichiers produits par l'(les) auteur(s)
