Natural convection in a vertical enclosure with discrete heating, the aspect ration effect

The effects of distributed, constant heat flux sources and constant temperature heat sink on the buoyancy-induced fluid flow and heat transfer in a differentially heated, vertical cavity has been studied experimentally for a heater pitch-to-height ratio of 2 and cavity aspect ratios of 4.5, 9, 13.5 and 16.5. For the aspect ratio of 16.5, the pitch-to-height ratio of 6 has also been investigated. The buoyancy-induced fluid flow has been photographed using fine aluminum tracing particles in ethylene glycol. Temperatures of the surfaces and medium were measured with thermocouples. The experiments were conducted with ethylene glycol as the convective medium at power levers of, 0.21, 0.41, 0.62, 0.83, and 1.03 W/cm² (approximately). These experiments covered the range of average modified Rayleigh numbers (based on enclosure's width) from 4.31x10⁶ to 9.35x10⁷. The empirical data were presented in the form of correlations. The convective heat transfer data were corrected for heat losses and convection through substrate conduction. Under the prescribed boundary conditions, increasing the aspect ratio (fixed width) enhances heat transfer. Excellent agreement was achieved with the previously reported heat transfer results in the literature for (i) a miniature, flush heat source on a vertical surface, and for (ii) the arrays of protruded heating elements for both the vertical plate (unshrouded) and the channel (shrouded).