Effects of curved vortex generators on the air-side performance of fin-and-tube heat exchangers

Numerical simulations are performed to examine the thermal and flow characteristics of curved vortex generators (VGs) on the fin surfaces of fin-and-tube heat exchangers. The performance of VGs with different curvatures are evaluated at various attack angles. In addition, the effects of parameters including position, size and inclination angle are also investigated. The heat transfer performance and pressure loss are analyzed using the dimensionless parameters Nu/Nu(0), f/f(0), and R = (Nu/Nu(0))/(f/f(0))(1/3) with Re-Dc ranging from 405 to 4050. The numerical result reveals that the value of R shows an upward trend with the increase of Re-Dc, indicating a better thermal hydraulic performance is obtained at higher Re-Dc for the present study. It is also found that the VGs with a curvature of 0.25 show best thermal hydraulic performance and the highest value of R = 1.06 is achieved at an angle of attack of beta = 15 degrees. Further parametrical study reveals that when the VGs are deployed at a non-dimensional horizontal distance of S-1* = 0.232 and vertical distance of S-2* = 0.697, better thermal hydraulic performance is achieved. The VGs with a smaller height and larger inclination angle show better thermal hydraulic performance at low Re-Dc (Re-Dc < 1620), while at high Re-Dc the VGs with a larger height and smaller inclination angle present higher value of R.