Effect of Attack Angle of Concave and Convex Winglets Vortex Generators on Thermal-Hydraulic Performance of Fin and Tube Heat Exchangers with Field Synergy Principle

In fin and tube heat exchangers, the gas passing through the fin has a lower thermal conductivity than the fluid passing through the tube. The low thermal conductivity brings a high thermal resistance, which suppresses the heat transfer rate. A common practice to enhance fin-side heat transfer is to generate longitudinal vortex by mounting vortex generators (VGs) on the fin. This paper aims to investigate how longitudinal vortex generator (LVG) improves heat transfer and pressure drop. Numerical simulations were carried out to analyze three types of VGs. The installation of VGs was varied with the attack angle changing from 10 degrees, 15 degrees, to 20 degrees with a 1-3-4-7 VG arrangement on the tube. The flow velocity was expressed in Reynolds number (Re) between 364 and 689. The enhancement of heat transfer rate and improvement of pressure drop were analyzed between three types of VG, three different attack angles, and four types of winglet installation, compared to baseline. The simulation results show that the highest convective heat transfer coefficient (84.85%) was achieved by the VG composed of seven concave delta winglet pairs (CDWPs) at the attack angle of 20 degrees and Re = 689; CDWP VG provides the highest heat transfer improvement among all cases.