Impact of the angle of attack of longitudinal vortex generator on enhancement heat transfer for a wavy-fin compact heat exchanger with circular and elliptical tubes

Resumo

The growing industrial development over the last decades led to the improvement of several thermal
devices. Among the main types of equipment that have evolved in the last decades, heat exchangers stand out.
The present work investigates the heat transfer augmentation for a wavy-fin compact heat exchanger operating at
low Reynolds numbers, by combining longitudinal vortex generators. The computational modeling considers a
tridimensional model, for an incompressible, steady-state and turbulent flow. The heat exchanger with wavy fins
is evaluated considering circular and elliptical tubes for staggered arrangement combined with vortex generator
of delta-winglet and rectangular-winglet with aspect ratio of 2 and angles of attack of 15o, 30o and 45o. The heat
transfer was evaluated by Colburn Factor and the pressure drop by Friction Factor. In comparison with the
reference heat exchanger (without vortices generators), the results show an increase in the heat exchange of 41%
using the elliptical tubes associated with a rectangular-winglet vortex generator at the angle of attack of 45o. For
the friction factor, the configuration with rectangular-winglet vortex generators is higher than delta-winglet
vortex generator independently of the angle of attack. Moreover, the friction factor for circular tubes is higher
than elliptical tubes. Overall, the results showed that the compound passive technique is an efficient technique to
improve the heat exchange in the compact heat exchanger, allowing, among others things, the reduction of
materials for fabrication process and manufacturing.