Etude numérique des transferts thermiques convectifs avec nano-fluides.
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In this work, we present the study of convective heat transfers with nanofluid and entropy generation inside three selected configurations. Two computational codes (AnsysFluent 14 and house-Fortran) were used to solve the partial differential equations describing natural convection and mixed laminar flows. Numerical results obtained by these codes were validated with those found in the literature, and a good agreement was obtained. The study presented in this thesis is divided into three parts. The first part of this study is devoted to two-dimensional flow in a vertical channel with parallel plates traversed by a Cu-water nanofluid. The effects of Reynolds and Grashof numbers, and the nanofluid solid volume fraction on heat transfer and entropy generation are examined in detail. The results show that increasing the nanoparticle volume fraction and dimensionless numbers (Re, Gr) improves the heat transfer rate and decreases the entropy generation in the channel. The second part presents the axisymmetric flow of an Al2O3-water nanofluid between two vertical coaxial cylinders. The effects of Rayleigh, Hartmann numbers, inclination angle and solid volume fraction of nanoparticles on heat transfer and entropy generation are studied in detail. Results reveal that the heat transfer and entropy generation rates depend on the intensity and orientation of the magnetic field. In addition, in all cases, the average Nusselt number and the total entropy generation increase by increasing the Rayleigh number and the volume fraction of nanoparticles. The third part is based on heat transfer, stready state, in a horizontal cylindrical duct, traversed by a three-dimensional flow of a nanofluid subjected to a heat flux to the wall. The effects of Richardson and Hartmann numbers, solid volume fraction of the nanofluid, and the direction of the magnetic field on heat transfer and entropy generation are examined in detail. The results indicate that the heat transfer and entropy generation rates depend on the intensity and direction of the magnetic field. In addition, the increase in the number of Richardson and the volume fraction of nanoparticles increases heat transfer and entropy generation. Finally, the application of a radial magnetic field promotes a better convective heat exchange and minimizes the entropy generation.