DOUBLE-DIFFUSIVE CONVECTION IN A TWO-UPPER-PARTITION RECTANGULAR ENCLOSURE

Abstract

Experiments were conducted to obtain better criteria for the temperature and concentration distributions caused by double-diffusive convection under an electrochemical system in a two-upper-partition enclosure whose aspect ratio (Ar) was 0.5. Both the thermal and solutal buoyancies, which either cooperated or opposed one another, were induced from the sides. The temperature gradient was maintained and controlled using two separate constant-temperature baths that circulated heated or cooled water through a heat exchanger. We used a copper sulfate–sulfuric acid solution as both the working fluid and the electrolyte. An electrochemical method based on a diffusion-controlled electrode reaction was employed to create the concentration gradient. We used the shadowgraph recording technique to visualize and analyze the flow. Thermal Grashof numbers ranging from 4.08 × 105 to 8.16 × 105 and solutal Grashof numbers ranging from 2.55 × 106 to 6.15 × 106 were investigated. Cooperating and opposing cases with a fixed partition ratio (Ap = 0.25) and Grm are discussed in this work. Given the Sherwood number correlation, it is demonstrated that the mass transfer rate increased with the increasing thermal Grashof numbers. Results showed that the Sherwood number in the cooperating case is much higher than that in the opposing case, by 23.7% for the fixed Grm and that in the opposing case, the Sherwood number decreases by 11.1% with increasing Grm.