ABSTRACT
Natural convection is often the preferred mode of heat dissipation in a number of thermal energy systems like spent nuclear fuel casks, underground transmission cables and enclosed bus bars because it is a passive, inexpensive, reliable and noise-free method of heat transfer. Natural convection problems arising in these applications often involve coupled conduction and natural convection. The present investigation is a numerical study of conjugate natural convection in a horizontal circular annulus. The finite thickness outer wall and the heat generating inner solid cylinder are concentrically placed. The natural convection in the annulus is driven by the volumetric heat generation in the solid cylinder. The temperature distribution in the solid cylinder is an important quantity because it is related to the safety aspects of the system. Radial fins connect the inner cylinder to the outer circular wall in order to reduce the temperature of the heat generating cylinder. The governing equations are the continuity, redial momentum, tangential momentum, solid and fluid energy equations. The problem is solved using the FLUENT CFD code. Results are obtained for the flow field inside the annulus, temperature distribution in the fluid and solid regions, and the contribution of fins to heat dissipation. The cooling enhancement that occurs with fins is compared to the case of no fins.
Keywords: Horizontal annulus, Radial fin, Heat generation.
