DOUBLE-DIFFUSIVE NATURAL-CONVECTION IN A CLOSED ANNULUS

A numerical study for steady laminar double-diffusive natural convecti on within a vertical closed annulus is examined with constant temperat ure and mass species (concentration) differences imposed across the ve rtical walls. The annulus has an aspect ratio of 1 and a curvature rat io of 2, while the fluid Prandtl number is 7. In this paper the proble m is defined and the numerical solution procedure is validated. Moreov er, the effect of buoyancy ratio on the flow structure and the resulti ng heat and mass transfer rates is presented. It is determined that bu oyancy ratio is the primary factor that defines flow structure, includ ing concentration-dominated (buoyancy force) opposing flow, transition al flow, thermal-dominated flow, or concentration-dominated aiding flo w. The relationship for buoyancy ratios, in the range -10 less-than-or -equal-to n less-than-or-equal-to 10, and the average Nusselt and Sher wood numbers have been obtained for a thermal Rayleigh number of 50,00 0 and a Lewis number of 5. Future papers will include the effect of th ermal Rayleigh number, Lewis number, and various geometric parameters on the flow structure and heat and mass transfer.