A comparative study on the air-side performance of wavy fin-and-tube heat exchanger with punched delta winglets in staggered and in-line arrangements

The air-side heat transfer and fluid flow characteristics of wavy fin-and-tube heat exchanger with delta winglets are investigated numerically. The three-dimensional simulations are performed with renormalization-group (RNG) k − ɛ   model to lay the foundation for the design of the high-performance heat exchanger. The wavy fin-and-tube heat exchangers which have three-row round tubes in staggered or in-line arrangements are studied. The numerical results show that each delta winglet generates a downstream main vortex and a corner vortex. For the in-line array, the longitudinal vortices enhance the heat transfer not only on the fin surface in the tube wake region but also on the tube surface downstream of the delta winglet; for the staggered array, longitudinal vortices are disrupted at the first wavy trough downstream from the delta winglet and only develop a short distance along the main-flow direction, and the vortices mainly enhance the heat transfer of the fin surface in the tube wake region. The longitudinal vortices generated by delta winglet cause considerable augmentation of heat transfer performance for wavy fin-and-tube heat exchanger with modest pressure drop penalty. When ReDc=3000ReDc=3000, compared with the wavy fin, the j and f factors of the wavy fin with delta winglets in staggered and in-line arrays are increased by 13.1%, 7.0% and 15.4%, 10.5%, respectively.