NATURAL-CONVECTION IN A PARTIAL SECTOR-SHAPED ENCLOSURE - EXPERIMENTAL RESULTS

An experimental study of the buoyancy-induced motion and heat transfer in a differentially heated partial sector-shaped enclosure is carried out. Radial surfaces of the sector are heated and cooled isothermally while the circumferential surfaces are insulated. Water is used as the working fluid in experiments with sector angles alpha = 30, 45, and 90 deg for Rayleigh number in the range 4 x 10(8) less than or similar to Ra less than or similar to 3 x 10(9). Laser illumination/streak photography is used to visualize the flow. Steady laminar motion is observed, with flow structure qualitatively independent of sector angle except for the case alpha = 90 deg. Circulation intensity is found to increase modestly with sector angle. Convection energy transfer across the sector increases rapidly with respect to transport by conduction for increasing alpha. Total energy transport across the sector is a nonmonotonic function of sector angle due to the competing mechanisms of conduction and convective transport. The existence of a sector angle alpha*, which minimizes the cross-sector heat transfer rate, is discussed.