Effects of longitudinal vortex interaction on periodically developed flow and heat transfer of fin-and-tube heat exchanger

Longitudinal vortex generators (LVGs) are among the most popular actuators for generating longitudinal vortices for the fin-side heat transfer enhancement of heat exchangers. In order to obtain a better heat transfer performance, researchers always try to punch lots of vortex generators out of the fin surface. However, the increasing number of LVGs does not necessarily increase the heat transfer performance due to the interaction of longitudinal vortices meeting in the flow channel. The interaction of longitudinal vortices not only affects the intensity of longitudinal vortices but also the heat transfer enhancement. In this paper, the intensity of longitudinal vortices generated by LVGs is quantitatively studied in the fin side channel of flat-tube-bank-fin heat exchanger by using the parameter Se for secondary flow intensity. The effect of transverse pitches of LVGs on the interaction of longitudinal vortices is studied in detail. What is also studied includes the effects of interaction of longitudinal vortices on the intensity of longitudinal vortices and the characteristics of periodically developed fluid flow and heat transfer. The results present that the transverse pitches of LVGs are related to the interaction between longitudinal vortices. Also, the intensity of longitudinal vortices and the heat transfer performances of longitudinal vortices are obviously affected by the interaction of longitudinal vortices. Optimum transverse pitch of LVGs is necessary for the best heat transfer performance. Meanwhile, an undesired transverse pitch of LVGs should be avoided. (C) 2016 Elsevier Masson SAS. All rights reserved.