Three dimensional analysis of natural convection in a narrow vertical annulus closed at top and opened at bottom

Natural convection flow and heat transfer in a narrow vertical annulus located centrally above a reservoir has been studied. The fluid in the reservoir is heated up by a hot, isothermal bottom end wall. The flow characteristics has been analysed by observing flow topologies and contours of temperature. Results are presented for Rayleigh numbers in the interval [2000-20000]. The flow consist of steady, periodic and quasi periodic regimes. The stream trace plot in each case is found to contain correct number of singularities of different types, which is required for satisfying the Hunts criterion. The annulus geometry selected for the study is a simplified model of the narrow annulus of a typical nuclear reactor design. The variation of circumferential temperature obtained from the study provides a relevant data for the design of nuclear reactors and similar systems.