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ISSN Druckformat: 1940-2503
ISSN Online: 1940-2554
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NATURAL CONVECTION OF NANOFLUIDS IN A CAVITY INCLUDING THE SORET EFFECT
ABSTRAKT
Convection of a binary mixture in a cavity is studied numerically. The flow is driven by a buoyancy force due to an externally applied constant temperature difference on the vertical wall of the cavity, while the horizontal surfaces are impermeable and adiabatic. A nanofluid is used and the effects of the cross phenomenon "Soret effect" were considered in the analysis. The flows are found to be dependent on the particle concentration φ, the Rayleigh number RaT, the Lewis number Le, the solutal to thermal buoyancy ratio N, and the thermal boundary conditions. Numerical results for finite amplitude convection, obtained by solving numerically the full governing equations, are found to be in good agreement with the analytical solution based on the scale analysis approach. We have proposed a modified formulation of the conservation equations governing the flow and heat transfer of nanofluids, taking into account important changes of nanofluid thermal conductivity and viscosity as well as the spatial change of the particle concentration that is induced by the Soret effect. Results have shown that such an effect increases nanofluid heat transfer. The optimal particle volume concentration, which maximizes heat transfer, is estimated to be 2%. The increase of natural convection with nanoparticle concentration is weak in comparison to that found in forced convection.
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