Double-diffusive natural convection and entropy generation in an enclosure of aspect ratio 4 with partial vertical heating and salting sources

Double-diffusive natural convection with entropy generation in a two-dimensional enclosure with partial vertical heating and salting sources for an aspect ratio Ar = 4 is investigated in the current study. A numerical methodology based on the finite volume method and a full multigrid technique is employed. The effects of various parameters; the Rayleigh number (10(3) <= Ra <= 2 x 10(5)), the buoyancy ratio (-8 <= N <= 8), the source location (0 <= eta <= 3), the Lewis number (10 <= Le <= 100), and, the source length (0.25 <= d <= 2) on the flow patterns are analyzed. Correlations of average Nusselt and Sherwood numbers are established as a function of two parameters (Ra, d) and ( Le, d), respectively. The numerical outcome of the present study shows that, by increasing the Lewis number in the range 10-100, the heat and mass transfer rates are significantly enhanced. In terms of irreversibility phenomena at the steady case, comparison of total entropy profiles with respect to N shows that irreversibility criterion is dominated by entropy generation due to fluid friction. Especial attention is attributed to the periodic flow behavior that appears for N in the range (0.87-0.99) outside of which it remains steady. According to the entropy generation phenomena, total entropy generation Stot and Bejan number Be were observed to oscillate with the same frequency but in opposing phases and with different amplitudes. (C) 2013 Production and hosting by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.