Abstract
The present work is aimed at studying the performance of exponential fin by numerical simulation of the conjugate heat transfer problem of fully developed laminar flow through the finned annulus of a double pipe. The exponential fin shape has been considered for the first time in literature according to the knowledge of the authors. The governing partial differential equations are numerically solved by employing the discontinuous Galerkin finite element method. A comprehensive investigation of the effects of the ratio of thermal conductivities of the solid and fluid, the number of longitudinal fins, the ratio of radii of pipes and the fin thickness on the thermal performance of the finned duct has been carried out. It is found that significant gain in the Nusselt number may be achieved by increasing the ratio of conductivities. A value of the ratio greater than 500 may not be cost-effective. The exponential fin has been found to outperform the triangular fin by 0.02-15.09%. The study shows that in order to have optimal performance, a large number of higher and thinner fins will have to be augmented to a double pipe with larger ratio of radii. (C) 2016 Elsevier Ltd. All rights reserved.