Natural convection in horizontal cylindrical annuli with fins

Natural convection heat transfer between two horizontal concentric cylinders with two fins attached to inner cylinder was investigated numerically using finite element technique. Laminar conditions up to Rayleigh number Rai of 5*104 were investigated. Effects of annulus diameter ratio, Rayleigh number, fin length, and its inclination angle on this type of flow were investigated. The conductance thermal resistance of finned annuli was obtained using conduction analysis. The thermal resistance decreases as fin length increases i.e. as the fin is extended within the annulus gap and increases as annulus diameter ratio increases i.e. as annular gap thickness increases. The free convection data were represented in terms of the effective thermal conductivity ratio ke/k versus Rayleigh number Rai. Correlation for thermal conductivity ratio is proposed. © Faculty of Engineering Alexandria University.