“…The enhancement system of heat transfer is great significance in improving the performance of these applications. So to implement this goal, many techniques such as (twisted tape, coils, louvers, rings, etc…) can be inserted in heat exchangers to augmentations heat transfer convection by increasing turbulent intensity [2].The earliest works on augmentation, Eiamsa-ard, Promvonge [3], investigated experimentally the convective heat transfer and friction factor characteristics in citcular tube with V-nozzle inserts at a uniform heat flux.Three pitch ratios (PR) of V-nozzle were considered in this study (PR==2.0, 4.0, and 7.0).The results showed that V-nozzle have a significant effect on the enhancement of heat transfer rate at about 27% over plain tube. It is found that the smaller pitch ratio (PR=2.0) gives a maximum enhancement about 1.19 due to reverse/ re-circulation flow.…”