This paper analyzes heat transfer and fluid flow of natural convection in inclined cavityfilled with CuO-water nanofluid and differentially heated. Conservation of mass, momentum, and energy equations are solved numerically by control volume finite element method using the SIMPLER algorithm for pressure-velocity coupling. The Prandtl number is fixed at 7.02 corresponding to water. Aspect ratio and solid volume fraction are varied from 0.5 to 4 and from 0% to 4%, respectively. The inclination angel is varied from 0° to 90° and used as a control parameter to investigate flow mode-transition and the accompanying hysteresis phenomenon (multi-steady solutions). It is found that the efficiency of heat transfer is improved by the addition of nanoparticles into base fluid; however there is an optimum solid volume fraction which maximizes the heat transfer rate. Numerical results show also that the diameter of solid particle is an important parameter that affects the heat transfer efficiency, its impact is more important than the concentration itself. Effects of inclination angle on streamlines and on thermal Downloaded by [University of Auckland Library] at 13:38 29 March 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 boundary layer are presented. Combined effects of aspect ratio and inclination angle on heat transfer and hysteresis region are analyzed.
The structures and stabilities of Na 2 + Xe n (n=1-6) clusters have been investigated by using an accurate ab-initio approach and an analytic potential form for the Na + -Xe and Xe-Xe interactions. The potential energy surfaces of the Na 2 + (X 2 Σ g + )-Xe n (n=1-6) clusters have been performed for a fixed distance of Na 2 + (X 2 Σ g + ) in its equilibrium distance. For n=1, the potential energy surfaces have been computed for an extensive range of the remaining two Jacobi coordinates, R and γ. In addition, we have determined the potential energy surfaces of 15 isomers of the Na 2 + (X 2 Σ g + )-Xe n (n=1-6). The potential energy surfaces are used to extract the spectroscopic informations on the stability of the Na 2 + (X 2 Σ g + )Xe n (n=1-6) clusters. For each n, the stability of the different isomers is examined by comparing their potential energy surfaces.We find that the most stable isomers are C ∞v (11), D ∞h (21), C 2v (31), D 2h (41), C 3v (51) and (61). To our knowledge, there are no experimental and theoretical studies on the collision between the Na 2 + (X 2 Σ g + ) alkali dimer and the Xenon atom.
A two-dimensional steady laminar natural convection in rectangular enclosure filled with CuO-water nanofluid is numerically investigated. The horizontal walls are thermally insulated and the left vertical side one is heated by a temporal sinusoidal temperature variation, whereas the right wall is kept at cold temperature. Mass Conservation, momentum, and energy equations are numerically solved by the finite volume element method using the SIMPLER algorithm for pressure-velocity coupling. This study has been carried out for four parameters: the volumetric fraction of nanoparticles (0%≤≤4%), aspect ratio Ar (0.25≤Ar≤1), amplitude of temperature a (0.2≤a≤0.8) and its period (0.2≤Θ≤0.8). These simulations are performed at constant Rayleigh and Prandtl numbers (Ra=10 5 and Pr=7.02). Numerical results show that the addition of nanoparticules into the basic fluid has a double role, increasing heat transfer and reducing the response time of the system. The decreasing of aspect ratio shows an increasing trend of the heat transfer and increases the amplitude of Nusselt number. We also see that after a time period the system does not return to its initial state (hysteresis phenomenon) because of the system inertia.
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