COMPARISON OF NATURAL-CONVECTION OF WATER AND AIR IN A PARTITIONED RECTANGULAR ENCLOSURE

A numerical solution comparing steady natural convection of water and air in a two dimensional, partially divided, rectangular enclosure is presented. Rayleigh numbers investigated range from 10(6) to 10(8), and the opening ratios studied are 0, 1/4, 1/6, and 1/8 respectively. To obtain a comparative study, Prandtl number of 7.0 (for water) and Prandtl number of 0.71 (for air) are used for the two working fluids. This study demonstrates that the conventional use of water to model air convection in partitioned enclosures gives reasonable heat transfer results. The average Nusselt number obtained for water is only 2 approximately 5% larger than that for air at the same conditions. The flow configuration and exchange flow rates for water and air are, however, different. The exchange flow rate for water is found to be 10 approximately 20% larger than that for air. It is observed that for the opened partition the average Nusselt number is 13 approximately 24% larger than that for unopened partition. On the other hand, an opening in the partition reduces the exchange volume flow rates by 5.68 approximately 15.2% for water and 1 approximately 11.4% for air. depending on the Rayleigh number and the opening ratio.