ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 3, Issue 4, October 2013 455 Abstract— Steady, laminar, double diffusion natural convection flow in a square enclosure with partially active vertical wall is considered. The enclosure is filled with a binary fluid and subjected to horizontal temperature and concentration gradients. The flow is driven by cooperating thermal and solutal buoyancies. The active location vertical left side wall and fully active vertical right side wall are maintained at two different but uniform temperatures and concentrations. The remaining boundaries are impermeable and thermally insulated. Finite volume method is used to solve the dimensionless governing equations. The physical problem depends on five parameters: thermal Rayleigh number (Rat =10 3 -10 6 ), Prandtl number (Pr=7), Schmidt number (Sc=240), buoyancy forces ratio (N=1) and the aspect ratio of the enclosure (A=1). The main focus of the study is on examining the effect of Rayleigh number on fluid flow and heat and mass transfer rates. The active location takes three positions in the left wall: top (T), middle (M) and bottom (B). The results including the streamlines, isotherm and iso-concentration patterns, flow velocity and the average Nusselt and Sherwood numbers for different values of Rat. The obtained results show that the increase of Rat leads to enhance heat and mass transfer rates. Also the position of the active location has a noticeable effect on the rate of heat and mass transfer and fluid velocity. Index Terms— Active location vertical wall, binary fluid, cooperate buoyancies, Thermosolutal natural convection. I. INTRODUCTION Natural convection, in which the buoyant forces are due both to temperature and concentration gradients, is generally referred to as thermosolutal convection or double-diffusive convection. Various modes of convection are possible depending on how temperature and concentration gradients are oriented relative to each other as well as to gravity. The stratified fluid can be subjected to horizontal or vertical temperature and concentrations gradients [1]. This phenomenon is of considerable interest in a very wide range of fields. In nature such flow is encountered in the oceans, pollution dispersion in lakes, shallow coastal waters and the atmosphere [2]. In industry, examples including chemical process, material processing such as: solidification of binary alloy, oxidation or surface materials, cleaning and drying operations, liquid gas storage, the fouling of piping and fluid storage components and energy storage in solar ponds, [2, 3]. Thermosolutal convection is also important in crystal growth processes. It is induced when the non uniform distribution of impurities occurs in the fluid phase. The quality of the growing crystal is severely affected by the melt convection and any oscillations are disadvantageous [4]. Convection in binary fluids is more complex than in pure fluids because of the difference in time scale diffusion between energy and species [3]. The species gradients may be induced by the solutal boundary conditions applied on the system (double diffusive problem) (Ostrash et al. [5], Lee et al. [6], Benacer et al. [7], Gobin et al.[8] and Sezai et al. [9]). It can also be induced by thermal gradients via the Soret effect [2, 3]. Thermosolutal convection was widely experimentally and numerically studied for several non- dimensional parameters namely the Lewis and Prandtl numbers, the buoyancy ratio, and for either cooperating or opposing heat and mass gradients. We shall refer to some important works that may serve as background for the present work. Kamotani et al. [1] studied experimentally the phenomenon of natural convection in rectangular enclosures with combined horizontal temperature and concentration gradients. Various complex flow patterns are observed with different experimental conditions. Temperature distributions, mass transfer rates and flow instability are also reported. An analytical and numerical studies of natural convection in enclosures filled with binary fluids with Neuman boundary conditions are studied by Ouriemi et al. [2, 3]. Both double diffusive convection and Soret induced convection are considered. The authors proposed an analytical solution based on the parallel flow approximation. In the above studies thermosolutal convection is due to the imposed temperature and concentration gradients between the opposite walls of the enclosure taking the entire vertical wall to be thermally active. But in many engineering applications such as solar energy collectors it is only a part of the wall which is thermally activated. Many articles concerning natural convection in enclosures with partially active walls had been published [10 -17]. For example Nithyadevi et al. [17] studied numerically the effect of double diffusive natural convection of water in a partially heated enclosure with Soret and Dufour coefficients for either cooperating or opposing heat and mass gradients Steady Laminar Cooperating Double Diffusion Natural Convection of Binary Fluid in a Square Enclosure with Partially Active Vertical Wall Abdennacer BELAZIZIA, Smail BENISSAAD, Said ABBOUDI