Impact of Bionic Fins on Supercritical CO₂ Serpentine Microtube in Various Flow Directions

In supercritical carbon dioxide (S-CO₂) serpentine microtube heat exchangers, heat transfer deterioration often occurs at the bend of serpentine microtube, which reduces the efficiency and shortens the lifetime of the tube. To solve this problem, RNG k-ε turbulence model is used to simulate the flow and heat transfer of S-CO₂ when bionic fins are added. The results show that adding fins can significantly improve heat transfer, especially at low mass flux. By increasing the length of the long axis and short axis of the fins, the heat transfer efficiency is significantly improved, but the flow resistance is also increased. When the long axis and short axis are increased in the same proportion, the effect of increasing the short axis on the heat transfer performance is more obvious. This study provides a new way to strengthen the design of S-CO₂ serpentine microtube heat exchangers, which has great potential for practical application.