There were many numerical studies concerning the simulation of LVG in the fin-and-tube heat exchangers [11–20] , some recent studies [16–20] had focused on the optimization of the implementations. Among these recent efforts, Jang et al. [16] investigated the optimum span angle and transverse location and the effect of different inlet conditions. The results showed that the maximum area reduction ratios reached 14.9–25.5% for the inline arrangement, and 7.9–13.6% of the maximum area reduction ratio was achieved for the staggered arrangement. Hu et al. [17] numerically studied
the relationship between the intensity of secondary flow caused by vortex generator of fin-and-tube heat exchangers, and proposed a dimensionless parameter to characterize the intensity of secondary flow. Li et al. [18] proposed a radiantly arranged LVGs for performance improvement of the fin-and-tube heat exchangers. Their numerical results showed that the arrangement of LVGs is totally different from existing publications. In addition to the implementations of LVGs on the fin-and-tube heat exchangers, some other numerical efforts stressed on the LVGs on louvered fin-and-tube heat exchangers [21–23] . Note that most previously published researches aimed at concerning the performance of LVG on fin-
and-tube heat exchangers, and only very few studies had actually experimentally implemented VG in the actual fin-and-tube heat exchangers.