NATURAL-CONVECTION IN SLENDER CAVITIES WITH MULTIPLE FINS ATTACHED TO AN ACTIVE WALL

Numerical solutions, based on the streamfunction-vorticity formulation, were obtained for two-dimensional flow of air in a differentially heated, slender cavity with conducting fins on the cold wall, for Rayleigh numbers of 10(3)-10(5), angles of inclination of 45-degrees and 90-degrees, overall aspect ratios of 20 and infinity, and microcavity aspect ratios (A') of 20-0.25. As A' was decreased from a value of 20, the flow pattern evolved as follows: a primary circulation state, a boundary layer regime with recirculations and decreasing primary circulation, an increase in primary circulation, a separation of the recirculating stream from the interfin space, and a final state of primary circulation restricted to the unfinned side. The average Nusselt number at a given fin length also evolved during these transitions, showing maximum and minimum values whose locations depended only on Ra. Limited results showing the dependence of flow and heat transfer variables on dimensionless fin length are also given. A series of recommendations are given for the thermal design of double-pane windows and flat plate solar collectors.