Abstract A novel approach to visualize the flow boiling inside a clear micro-fin tube under diabatic conditions is presented. Transparent smooth, axial micro-fin, and helical micro-fin tubes are made by 3D printing. The 3D printed tube is placed inside a glass tube and heated by the transparent secondary fluid flowing between the two tubes for providing the evaporation conditions and transparency. R410A flow boiling and the flow patterns in the three geometries captured with a high speed camera are compared. The experimental results show that micro-fin geometry influences flow behavior. Bubbles are mainly generated in the groove region due to a higher superheat than the fin region. Some of the liquid refrigerant is trapped in the grooves of the upper part of the micro-fin tube when the slug flow is present, and bubbles are generated in this thin liquid layer. In addition, the bubbles in the helical micro-fin tube are easier to merge because of the obstacle of the fin geometry for the bubble flowing path. As the two bubble merge, the conversion of surface free energy causes the bubble to travel with a higher velocity.

中文翻译：

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非绝热可视化显示微翅片对 R410A 蒸发的影响：平滑、轴向微翅片和螺旋微翅片管

摘要 提出了一种在非绝热条件下可视化透明微翅片管内流动沸腾的新方法。透明光滑、轴向微翅片和螺旋微翅片管由 3D 打印制成。3D 打印管放置在玻璃管内，并由在两管之间流动的透明二次流体加热，以提供蒸发条件和透明度。比较 R410A 流动沸腾和高速相机拍摄的三种几何形状的流动模式。实验结果表明，微翅片几何形状影响流动行为。由于比翅片区域更高的过热度，气泡主要在凹槽区域产生。当存在段塞流时，部分液态制冷剂被困在微翅片管上部的凹槽中，在这薄薄的液体层中产生气泡。此外，螺旋微翅片管中的气泡更容易合并，因为翅片几何形状对气泡流动路径的阻碍。当两个气泡合并时，表面自由能的转换使气泡以更高的速度行进。