This paper experimentally investigates the factors influencing the flow boiling heat transfer of R134a refrigerant within smooth and micro-fin tubes having an outer diameter of 9.52 mm. The tube has a peculiar micro-fin shape with a 46° apex angle and 22° helix angle, producing a surface area 1.62 times bigger than a smooth tube of identical diameter. The main goal of the study is to understand the influences of mass flux, heat flux, saturation temperature, and average vapor quality on heat transfer characteristics. The findings are initially compared with known flow boiling correlations; moreover, performance index, penalty factor, and enhancement factor considerations are also made. The heat transfer coefficient (HTC) relies on mass flux, with significant improvements at G = 200 kg m s, despite dry-out difficulties at high vapor quality. Intensified flow velocity from higher mass flux causes a rise in frictional pressure drop (FPD), with micro-fin tubes demonstrating superior heat transfer, owing to their larger surface area and improved swirl formation. Compared to smooth tubes, FPD is significantly influenced by vapor quality for micro-fin tubes. The study analyses the importance of micro-fin tubes to improve heat transfer in industrial applications, as well as the effects of saturation temperature and vapor quality on HTC.

中文翻译：

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探索微翅片管对使用 R134a 制冷剂的流动沸腾传热影响的新方法：参数案例研究


本文通过实验研究了外径为9.52 mm的光滑微翅片管内R134a制冷剂流动沸腾传热的影响因素。该管具有独特的微翅片形状，顶角为46°，螺旋角为22°，表面积比相同直径的光滑管大1.62倍。该研究的主要目标是了解质量通量、热通量、饱和温度和平均蒸汽品质对传热特性的影响。研究结果最初与已知的流动沸腾相关性进行了比较；此外，还考虑了性能指标、惩罚因子和增强因子。传热系数 (HTC) 依赖于质量通量，尽管在高蒸汽质量下存在干燥困难，但在 G = 200 kg ms 时显着改善。较高质量通量带来的流速增强会导致摩擦压降 (FPD) 上升，而微翅片管由于其较大的表面积和改善的旋流形成而表现出卓越的传热性能。与光滑管相比，微翅片管的 FPD 受到蒸汽质量的显着影响。该研究分析了微翅片管在工业应用中改善传热的重要性，以及饱和温度和蒸汽质量对 HTC 的影响。