Laminar Mixed Convection in Two Concentric Vertical Cylinders

The flow patterns and heat transfer have been studied numerically for contained air in the space formed by two vertical concentric cylinders. The inner cylinder rotates about its vertical axis and the outer cylinder is kept stationary. This geometry simulates, for example, the gaps at the ends of the rotor of vertical electric motors. The results facilitate the thermal design of such devices. The governing equations for velocity and temperature are solved by finite volume techniques in which the SIMPLE algorithm is incorporated. Results are presented for a range of Reynolds numbers (Re) and for various values of aspect ratio. It has been found that for high values of Re, the flow is dominated by centrifugal forces whereas for low values of Re the flow is dominated by gravitational buoyancy. To facilitate the use of results for design, some correlations were developed which represent the heat transfer coefficient as a continuous function of the investigated independents parameters.