A numerical study of the effect on flow structure and heat transfer of a rectangular winglet pair in a plate fin heat exchanger

Longitudinal vortices have a great capability of disrupting the growth of boundary layers and bring about the heat transfer enhancement between the fluid and its neighbouring surface. The potential of a winglet pair type vortex generator for the heat transfer enhancement in a plate fin heat exchanger, with triangular fins as inserts, is numerically evaluated in this article. The rectangular winglet pair is mounted on the triangular fins. The numerical computations are performed by solving an unsteady, three-dimensional Navier-Stokes equation, and an energy equation by using the modified MAC method. Air is taken as the working fluid. This study shows the flow structure and the performance of the winglet pair in improving the heat transfer. The computations are performed at Re = 200 and placing the winglet at an angle of attack, beta = 20 degrees. The results show that the heat transfer is increased by 13 per cent, even at the exit, with the winglet pair. The heat transfer enhancement with a winglet pair for different Re = 200-500 and Pr = 0.71 and for varying heights of the winglet pair is also predicted.