Quantitative relationship between secondary flow intensity and heat transfer intensity in flat-tube-and-fin air heat exchanger with vortex generators

Abstract

Secondary flow can greatly enhance the convective heat transfer with less pressure loss and has been applied broadly for heat transfer enhancement. But researchers often describe the secondary flow qualitatively and the quantitative relationship between secondary flow intensity and heat transfer intensity is still not thorough. In this paper, the quantitative relationship between the secondary flow intensity and heat transfer intensity is numerically studied in the fin-side channel of flat-tube-and-fin air heat exchanger. The secondary flow intensity is quantified using the non-dimensional parameter Se. Both the secondary flow intensity and heat transfer intensity change along with the change of fin and vortex generator configurations. There is no corresponding relationship neither between Nu and Re nor between f and Re. However, a corresponding relationship can be found between Nu and Se, which indicates that the secondary flow intensity determines the heat transfer intensity in the fin-side channel of flat-tube-and-fin air heat exchanger with vortex generators on the fin surfaces.