Key words: Nanofluid, Natural convection, Partially active walls, Inclination angle.

Abstract: Effects of inclination angle on natural convection heat transfer and fluid flow in an enclosure with partially heated side walls filled with cu-water nanofluid has been analyzed numerically. A two heat sources maintained at a constant heat flux q’’ are embedded in the right and the left wall. The enclosure was cooled from the top and bottom walls. The remaining boundary parts are kept insulated. The angle of inclination is used as a control parameter for improve flow and heat transfer enhancement depicted in our recently work. Using a home developed code a parametric study is conducted and a set of graphical results is presented and discussed to illustrate the effects of inclination angle on the flow and heat transfer characteristics. The inclination angle was varied from 0 to 90° and two mainly case are considered, namely Middle-Middle (MM) and Down-Top (DT) depending of the two vertical sources location along the two side walls. It is found that optimal heat transfer enhancement can be improved. A percentage of heat transfer enhancement using 10% of Cu- nanoparticles is obtained for an inclination angle of 15° at higher Rayleigh number (Ra=105).

Key words: Numerical method, Soret effect, entropy generation, porous medium, cavity, double diffusive convection.

Abstract: This paper consists of a numerical investigation about the influence of Soret effect on entropy generation in double diffusive convection. It consists of a square porous Darcy – Brinkman cavity saturated by a binary perfect gas mixture and submitted to horizontal thermal and concentration gradients. The Control Volume Finite-Element Method was employed in order to solve the set of equations describing the studied phenomena. Influence of the Soret effect on the different irreversibilities was carried out by the variation of the thermal diffusion ratio and the Darcy number. Taking into consideration the Soret effect induces an increase of heat transfer and viscous irreversibilities. The diffusive entropy generation presents different behaviours.

Keywords: 3D cavity, entropy generation, natural convection, double diffusive

Abstract:In this paper we study numerically the 3D double-diffusive natural convection in a cubic cavity. The main purpose of this paper is to study the effect of the modification of the boundary condition of the upper and down sides of a cubical cavity, on the flow and heat transfer in the one side and on the entropy generated on the other side. The flow is considered laminar and caused by the interaction of thermal energy and the chemical species diffusions. The governing equations of the problem, concentration, energy and momentum, are formulated using vector potential-vorticity formalism in its three-dimensional form, then solved by the finite volumes method. The Rayleigh number is fixed at Ra=105 and the effects of the buoyancy ratio is studied for opposed temperature and concentration gradients. The particular interest is focalized on the three-dimensional aspects and entropy generation.

Key words: Rayleigh-Bénard; Magnetoconvection; Entropy; Hartmann number.

Abstract: The present paper focuses, in particular, on aspect ratio (AR) effects on Rayleigh-Bénard convection within enclosure under a uniform magnetic field. Results are presented and analyzed for different values of Hartmann number (60≤ Ha ≤ 80) and for a range of aspect ratios (0.75≤AR≤1) at various Rayleigh numbers (Ra). It is found that both enclosure aspect ratio and magnetic field intensity play a significant role in controlling the onset of the Rayleigh-Bénard convection flow. The entropy generation analysis demonstrates that irreversibility phenomena increase for lower aspect ratio values and moderate Hartmann numbers.

Keywords: Convection, thermosolutal, hydromagnetic, three-dimensional.

Abstract: In the present study, thermosolutal convection of fluid in a cubic enclosure filled with a binary mixture is numerically investigated in a strong magnetic field. The physical model is heated from left-hand side vertical wall and cooled from opposing wall. Above this enclosure an electric coil is set to generate a magnetic field. The numerical method in the present work is the formalism vector potential vorticity in a three-dimensional configuration using the finite volume method. The influence of the intensity of magnetic field on the three-dimensional flow, the distributions of temperature and concentration and the characteristics of heat and mass transfer are revealed. The results show that the magnetic force has significant effect on the three-dimensional flow structure and heat and mass transfer.