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 α = 30, 45, and 90 deg for Rayleigh number in the range 4 × 10⁸ ≲ Ra ≲ 3 × 10⁹. 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 α = 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 α. 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 α*, which minimizes the cross-sector heat transfer rate, is discussed.