Constructal design of cross‐flow heat exchanger with concave/convex fins

Abstract

A contractual design of cross‐flow heat exchanger with concave/convex fins under fixed pressure drop is presented in this paper. An array of heated concave and convex fins are placed in a fixed area, and they are cooled by incoming cross flow, which is moving towards the fins due to constant pressure drop. The distances from fin to fin, the fin base, and the fin surface curvature (concave and convex) are free to morph and are constrained by the fin length and the height of cross flow. Bejan's number ranges from 105 to 107. The ratio of fin base‐to‐fin length is changed from 0.1 to 0.3. The dimensionless mass, momentum, and energy equations for two‐dimensional, steady, and incompressible flow are solved based on the finite volume numerical method. Also, the scale analysis method is used to compare heat transfer densities from concave and convex fins. The numerical results showed that the maximal convective heat transfer density for convex fins is higher than that of the concave fins for all Bejan numbers. The augmentations in the maximal heat transfer density are 2.1% at Be = 105, 4% at Be = 106, and 12.5% at Be = 107. Also, this is confirmed by the scale analysis method.