Effects of convective instabilities on heat exchangers

The heat exchanger walls can be constituted by flat or corrugated plates, cylindrical or variable section ducts equipped with baffles of different shapes. For this purpose, this paper aims to demonstrate the advantage of using baffles to disrupt the fluid flow and thus the convective heat exchange instability during the generation of recirculation zones within the channel. The fluid used is hydrogen in a turbulent flow in forced convection. The baffles having a part inclined at an angle of 30, 45 and 60 are attached to upper and lower horizontal walls of a rectangular channel. Axial velocity profiles, velocity fields as well as the distribution of Nusselt number are presented. The baffles are involved in creating recirculation zones by creating convective heat exchange instability. The part of the baffle inclined at an angle of 30 is more efficient than other inclinations as the Nusselt number increases by about 26% more. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.