Heat Transfer Augmentation Using Dissimilar Porous Baffles in a\nBackward-Facing Step Flow

Abstract

This paper reports a numerical investigation of the use of a pair of baffles of dissimilar porosity as heat augmentation devices in a backward-facing step flow in a two-dimensional channel. The specific goal of this study is to explore the possibility of providing a pressure penalty-free heat transfer enhancement using such a pair of porous baffles in a laminar forced convection flow. The numerical simulations are done using a finite element-based COMSOL Multiphysics commercial software. The parameters studied include Reynolds number (100, 200, 300, 400, 500), porous baffle solid volume fraction φ (0.031, 0.125, 0.500), and the porous baffle streamwise location (0.5, 1.0, 1.5, 2.0, 2.5, 3.0 times the channel height). The results show that the porous baffles result in increments of the local peak Nusselt Numbers and global Nusselt numbers by up to 200% and 85% respectively with an increase in Reynolds number from 100 to 500. For the same pressure drop requirement, the average convection to conduction heat transfer is up to 16% better when a pair of baffles are used, compared to an unobstructed flow. For the channel tested in this work, the best location for optimal heat augmentation with least pressure penalty is reached both porous baffles are located at a streamwise distance ~2 times the channel’s expanded height.