Numerical analysis to vortex heat transfer enhancement based on field synergy principle

3-D numerical simulation results are presented for fin-and-tube heat transfer surface with vortex generators. The effects of Reynolds number (from 800 to 2000), the attack angle (30° and 45°) of delta winglet vortex generator are examined. The numerical results are analyzed based on the field synergy principle to explain the inherent mechanism of heat transfer enhancement by longitudinal vortex, namely second flow generated by the vortex generators causes the reduction of the intersection angle between the velocity and fluid temperature gradient. In addition, the computational evaluations indicate that the heat transfer enhancement of delta winglet for aligned tube bank heat exchanger is more significant than that for staggered tube bank heat exchanger, the heat transfer enhancement of delta winglet with the attack angle of 45° is more obvious than that of 30°; the delta winglet with the attack angle of 45° leads to an increase in pressure drop, while the delta winglet with the attack angle of 30° results in a slight decrease. The heat transfer enhancement per unit pumping power for attack angle of 30° is larger than that for attack angle of 45° either for staggered or for aligned tube bank arrangement.