| Abstrakt: |
In this work, the natural double diffusive convection in a rectangular cavity horizontally disposed, filled with Newtonian nanofluids, heated and salted by uniform heat and mass fluxes on its vertical walls while the horizontal ones are assumed thermally adiabatic and solutally impermeable, is studied analytically (parallel flow approximation) and numerically (finite difference method). The study parameters are: the aspect ratio, 1 ≤ A ≤ 14, the thermal Rayleigh number, 103 ≤ RaT ≤ 105, and the volume fraction of different types of nanoparticles, 0 ≤ φ ≤ 0.1. The effects of these parameters on flow intensity and on heat and mass transfer rates are presented and discussed in terms of the current function, average Nusselt and Sherwood numbers, and the characteristics of the flow are visualized in terms of the stream lines, isotherms and isoconcentrations. Within the limits of the considered values of the governing parameters, the stream lines, isotherms and isoconcentrations showed, respectively, a parallel aspect and a thermal and solutal stratification in the central part of the cavity when A is large enough (A≥10). This proved the existence of an analytical solution which agreed perfectly with the numerical one. This analytical solution allowed us to fit correlations for the Nusselt and Sherwood numbers as functions of the thermal Rayleigh number and the volume fraction of different types of nanoparticles. The results obtained by examining the interest of using nanofluids in the considered configuration were against all expectations, that they led to a degradation of the rates of heat and mass transfers. [ABSTRACT FROM AUTHOR] |
