The delta winglet vortex generators can significantly enhance the heat transfer in tube bank fin heat exchangers with a moderate pressure loss penalty. The height of vortex generator has a great influence on the fluid flow and heat transfer of heat exchanger. The effects of height of delta winglet vortex generators on intensity of secondary flow and heat transfer performance of a circular tube bank fin heat exchanger were investigated numerically. Three different heights of vortex generators 1.5

1.75 and 2.0 mm were studied. The results show that under the same Reynolds number

the values of Nusselt number

friction factor and longitudinal vortex intensity all increase with increasing the height of vortex generators. There is one-to-one correlation between the volume average non-dimensional intensity of secondary flow and Nusselt number for all the cases that studied

but there is no such correlation with the friction factor. To screen the optimal height of vortex generators

an appropriate evaluation criterion JF is used and we obtain that the comprehensive heat transfer performance is best if the height of vortex generators is 1.75 mm for the studied cases.