Contribution à l’étude des transferts thermiques dans les nanofluides.

Abstract

his thesis deals with the numerical modelling of laminar natural and mixed convection flows of different anofluids types. Numerical simulations were performed using Ansysfluent software, considering three configurations: the square cavity, the cubic cavity, and the inclined channel. The numerical results obtained were validated with those found in the literature. A good agreement was obtained. We present three parts grouping the treated configurations: The first part concerns the study of 2-D natural convection in a square cavity equipped with a pentagonal obstacle, filled with a nanofluid (Cu/Water). The effects of the Rayleigh number Ra, the volumetric concentration of nanoparticles , the aspect ratio r and the orientation of the block were discussed The second part examines the 3-D mixed convection inside a cubic cavity with a heated square-section obstacle. This study compares the single carbon nanotube CNT/water nanofluid and the hybrid CNT-Copper/water nanofluid with different concentration ratios, Richardson number Ri, Reynolds number Re, and block aspect ratio r. In this case, three correlations have been developed to predict the average Nusselt number Nu's variation as a function of the chosen parameters. The third part deals with the numerical study of laminar mixed convection with entropy generation in an inclined channel with four heated blocks, traversed by a hybrid Al2O3- Cu/water nanofluid. In this part, the use of a two-phase mixing model approach was considered to demonstrate the effects of several parameters such as Ri, Re, , θ (the channel tilt), and the position of the block on Nusselt number, entropy generations, and Bejan number. Two different correlations were also determined to express Nu's average values for the position of aligned and non-aligned blocks.