Effects of delta winglet vortex generators on flow of air over in-line tube bank: A new empirical correlation for heat transfer prediction

The present work performs an experimental study addressing the effects of delta winglet vortex generators on convective heat transfer rate at in-line tube bank in external cross flow. The main goal of the work is to evaluate a study assessing the influences of the following parameters on convective heat transfer enhancement: the distance from the vortex generators to the tube bank, the pitch and the incidence angle of the delta winglet, as well as the free-stream velocity inside the wind tunnel (Reynolds number). The validation of the experimental methodology employed was performed by comparing the present results with empiric correlations available in the literature. The main results indicate that Nusselt number was enhanced when using turbulence promoters, being the maximum increment around 30%. Otherwise, the pressure drop through the tube bank was enhanced accordingly, being the maximum increment around 40%. Finally, it is worth mentioning that all the experimental results for the Nusselt number were condensed in a new empirical correlation for practical applications with good accuracy (maximum error around ± 6.0%).