Numerical study of natural convection in vertical cylindrical annulus with internal heat generation

Natural convection with internal heat generation phenomena in a fluid with volumetric heat generation has primarily applicable to the nuclear industry. However, natural convection in the vertical double-passage annuli with internal heat generation has possible applications in the radioactive waste heat removal, electrolytic processing, geothermal energy recovery, nuclear fusion and exothermic chemical reactions. In this paper, the buoyant convection in vertical double-annuli formed by three co-axial cylinders has been analyzed numerically. The inner and outer cylinders are respectively maintained by higher and lower thermal conditions, while the heat flux continuity condition is imposed on the middle cylinder, which is assumed to be thin and perfectly conductive. However, the upper and lower boundary regions are kept thermally insulated. Using the time splitting and over relaxation based finite difference methods, the model equations are numerically solved to understand the flow movements and thermal transport processes in the two annular passages. Among the different parameters of the problem, the position of middle cylinder is found to have significant influence on the flow distribution and thermal transport rates. Also, the transient variation of thermal transport has been captured successfully through our numerical simulations.