Freeform winglet design of fin-and-tube heat exchangers guided by topology optimization

This paper presents a novel winglet design of a fin-and-tube heat exchanger, and its performance regarding heat transfer enhancement is numerically investigated. In this study, the fin pattern is designed considering the shape, arrangement, and number of the winglets, because a higher degree of freedom for the structural design results in further improvement of the performance. To obtain promising features for the winglet design, topology optimization is applied in a simplified model that incorporates key factors of the physical phenomena. The optimization problem is formulated as a maximization problem of the heat extraction by the winglets in a two-dimensional simplified model under lowered Reynolds number flows. The optimized configurations are evaluated via three-dimensional high-fidelity analyses to obtain a promising design candidate. A manufacturable fin pattern is then designed from the promising candidate. The results indicate that the gradually curved winglets along the flow can enhance the heat transfer at a moderate pressure loss. The proposed fin demonstrates up to 16.0% improvement in the quality factor j/f compared with a fin with rectangular winglet pairs.