Heat Transfer and Flow Characteristics of a Finned-tube according to the Combined Arrangement of Curved Delta Winglet Vortex Generators

In this paper, A numerical analysis was performed to investigate effects of the Curved Vortex Generator(CVG) on heat transfer and flow characteristics of the finned-tube heat exchanger. The Delta Winglet Downstream(DWD) CVGs and Delta Winglet Upstream(DWU) CVGs were applied which placed on upstream and downstream of the tube, respectively. The DWD CVGs were fixed at α= 30 °, upstream of the tube, while only the position of the DWU CVGs were adjusted to figure out the effects. As the result, the closer DWU CVGs are to the tube, the smaller flow separation region of the tube. In addition, the DWU CVGs occur heat transfer enhancement on overall channel. This trend is commonly appeared at both α= 105 °and α= 120 °. DWU CVGs at α= 105 ° and α= 120 ° with DWD CVGs, the lower r/R results in the higher thermal performance factor. And the factors are increased by 39 % and 36 % compared to the plain finned- tube, respectively. Also, This increasement is higher than when applying a single pair of DWD CVGs or DWU CVGs. This results come from heat transfer enhancement by the mixed vortices of the DWD CVGs and the longitudinal vortices of the DWU CVGs, and reduction of separation region of tube by DWU CVGs.