Numerical investigation for the optimal placements of rectangular vortex generators for improved thermal performance of fin-and-tube heat exchangers

In the present work, a numerical investigation has been performed to find out the best emplacement of rectangular winglet pairs (RWPs) for the improvement of the heat transfer and flow characteristics of a fin and tube compact heat exchanger at low Reynolds number ranges from 500 to 900. The RWPs are placed at two different locations i.e., adjacent to the tubes and behind the tubes namely, common-flow-up (CFU) and common-flowdown (CFD) orientations respectively. The effect of attack angle, span angle and location of RWPs on air-side thermal hydraulic performance is investigated numerically. Area goodness factor and heat transfer rate per unit fan power are considered as the performance evaluation criteria. It is found that with the increase in attack angle and span angle heat transfer rate increases causing an increase in pressure drop penalty as well. Vortex generators behind the tube can reduce the pressure drop but with a significant reduction in heat transfer. Furthermore, MOORA (Multi-objective optimization by ratio analysis) method is employed to obtain the most expedient position and orientation of RWPs.