In presented work, numerical analysis of heat transfer and pressure drop using vortex generators in fin and flat tube heat exchanger has been presented. Conjugate heat transfer 3D numerical model has been developed and successfully carried out. Rectangular winglets were set in pairs, with downstream orientation. The effects of impact angles of 5 degrees, 10 degrees and 20 degrees as well as winglet height were examined through Nu number and j/f factor. Reynolds number is ranged from 350 to 2200. The numerical results showed that in the range of the present study, the variation of these parameters can result in the increase of heat transfer but with a penalty of pressure drop. Pressure drop increases for larger impact angles and with winglet height. Optimum heat transfer without significant pressure drop increase gives the vortex generator geometry of 0.64 x 1.92 mm (i.e. winglet height equals 2/3 fin spacing) with impact angle 10 degrees. (C) 2014 Elsevier Ltd. All rights reserved.