Investigation of Natural Convection in Partially Divided Rectangular Enclosures Both With and Without an Opening in the Partition Plate: Measurement Results

Experimental results are presented for steady natural convection in a two-dimensional, partially divided, rectangular enclosure, in which two of the vertical walls were maintained at different uniform temperatures and the top and bottom walls were insulated. The partition plate was adiabatic, and the experiment was carried out both with and without an opening in the partition. Rayleigh numbers ranging from 10⁶ to 10⁸ and opening ratios of 0, 1/8, and 1/4 were investigated for an enclosure aspect ratio (length/height) of 2 and Prandtl number of 7 (for water). Local velocity and temperature measurements were made with a laser-Doppler velocimeter and thermocouple probes. Flow visualization using colored dye was also performed. Results show that there was a recirculation zone in the upper and left quadrant of the enclosure when there was no opening in the partition plate. With an opening in the partition, the recirculation zone was absent and the heat transfer rate increased. An unopened partial obstruction would reduce the heat transfer rate by an amount of 12 to 30 percent depending on the Rayleigh number. However, the opening seems to have little effect on the velocity and temperature profiles of the left-moving fluid on the bottom wall. A correlation of the Nusselt number is derived, which shows that the heat transfer rate increases as the Rayleigh number or opening ratio increases.