Numerical investigation of a finned-tube heat exchanger with novel longitudinal vortex generators

A novel longitudinal vortex generator (LVG), which is comprised of a modified rectangular wing and an accessory trapezoidal wing, was proposed. The performance of finned-tube heat exchanger with a single row of novel combined winglet pairs (NCWPs) was analyzed. Numerical simulation shows that compared with rectangular winglet pair (RWP), the NCWP generates main vortex with larger centric intensity. Furthermore, the accessory vortex has a lower core and flows into the back of tubes compressing wake regions' size behind tubes due to the influence of accessory wing. It can disturb the developing of boundary layers on the bottom fin and enhance effectively the heat transfer of the wake region behind the tube. Therefore, the performance of heat transfer for finned-tube heat exchanger is significantly enhanced by NCWP with a moderate pressure drop penalty. Compared with the heat exchanger without LVGs, the heat transfer for finned-tube heat exchanger with NCWPs is improved by 1.8-24.2%, with a pressure penalty increase of 1.3-29.1%. In addition, theory analysis and numerical simulation well agree with the experiment results, indicating the reliability of the research. (C) 2015 Elsevier Ltd. All rights reserved.