Enhanced Mixed Convection in a Vertical Channel by Addition of Staggered Inclined Baffles

Abstract

In this Paper, two-dimensional unsteady laminar fluid flow and heat transfer characteristics have been investigated numerically in a symmetrically heated vertical channel with inclined baffles. The baffles are attached on both walls in a staggered manner with constant spacing. OpenFOAM®, an open source code based on the finite volume method, is used to solve the governing equations with the adequate boundary conditions. Air () is used as working fluid. The effects of baffle tilt angle (30–90 deg), baffle height (0.25 and 0.5), Reynolds number (200–1200), and Grashof number ( to ) on heat transfer and friction factor in the steady state as well as in self-sustained oscillatory flow have been assessed. The results are given in the form of dimensionless isotherms contours and streamlines in addition to the Nusselt number and friction factor. The results obtained exposed that the flow bifurcates to self-sustained oscillatory flow at moderate Reynolds number (below 700 for a blockage ratio of 0.25 and all baffle tilt angles). When the flow becomes unsteady, a significant increase in heat transfer rate is observed compared to the steady-state flow. Heat transfer enhancement rate can reach 1.4 times in steady-state flow; however, the unsteady self-sustained flow leads to 2.5 times for baffle height and 3.5 times for baffle height at compared to the smooth channel. The results of this study bear utility toward designing efficient thermal systems that can provide maximum heat transfer with minimum pumping power.