The investigation of fully developed turbulent flow in circular annular duct

Effect of the fin geometry in the heat exchangers is one of the most significant parameter for the heat transfer and friction factor. In this study flow geometry and meshes designed by Gambit 2.4.6 software and numerical analysis performed in Fluent 12.0 software. The turbulent annular flow condition is assumed as hydrodynamically developed and thermally developing. The total number of fins attached on the inner wall is 20 and the effect of the fin hight and fluid velocity change to the Nusselt number and friction factor is investigated. Air is used as the flow material. Basic conservation equations are solved in the steady state three dimensional flow conditions. The flow was analyzed using k-? Realizable model. Obtained Nusselt numbers and friction factors for the flow are determined according to the Reynolds number correlated to Nu=aReb and f=cRed forms. The results obtained from numerical analysis are conformed with the experimental values from literature. In the case of not using the fins, Nusselt numbers and Darcy friction factors take the highest values. On the other hand with using fins, as the hight of the fin increases the Nusselt numbers and friction factor values are increased. In addition, increase of Reynolds number brings out the decrease of friction factor and increase of Nusselt number.