Simulation of flow structure and heat transfer enhancement in a triangular duct with rectangular wing

The improvement of the performance of heat exchangers with gas as the working fluid becomes particularly important due to the high thermal resistance offered by gases in general. In order to compensate for the poor heat transfer properties of gases, the surface area density of plate heat exchangers can be increased by making use of the secondary fins such as, off-set fins, triangular fins, wavy fins, louvered fins etc. In addition, a promising technique for the enhancement of heat transfer is the use of longitudinal vortex generators. The longitudinal vortices are produced due to the pressure difference generated between the front and back surface of the vortex generator. The longitudinal vortices facilitate the exchange of fluid near the walls with the fluid in the core and hence, the boundary layer is disturbed. It causes the increase in temperature gradient at the surface which leads to the augmentation in heat transfer. An innovative design of triangular shaped secondary fins with rectangular delta wing vortex generator mounted on bottom surface of the channel for enhancing the heat transfer rate in plate-fin heat exchanger is proposed. The computational details have been given for analysis of problem in the FLUENT 6.3 which mainly describes about the solution algorithm and solution schemes as well as the underrelaxation factors required for the present problem. As the solution is converged after certain number of iterations, the values of pressure drop and Nusselt number, Average temperature, friction factor are calculated for different angle of attack and for different locations at β=30° and compared for the same parameter of plain channel without rectangular wing.