Abstract

The article presents the results of an experimental study of heat transfer in boiling of downflow of refrigerant R-21 in an element of a plate-fin heat exchanger with perforated fins. The experiments were carried out at mass velocities of 20 and 50 kg/m²s and wall superheat of 0.97 to 1.3°C. The data obtained show no significant dependence of the heat transfer coefficient on the heat flux density and mass velocity, as well as significant heat transfer deterioration at vapor quality exceeding 0.75. The most probable mechanism of heat transfer under these conditions is the decisive influence of the heat transfer during the evaporation of thin liquid film curved by capillary forces in the presence of liquid-vapor-wall contact line. This result from calculations by a model that simultaneously takes into account two-phase forced convection, nucleate boiling with allowance for suppression of boiling, and evaporation of liquid film in the presence of contact line.

中文翻译：

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多孔壁微通道装配中R-21制冷剂下流过程中流动沸腾传热的实验研究

摘要

本文介绍了在带有穿孔翅片的板翅式换热器元件中制冷剂 R-21 向下流动沸腾传热的实验研究结果。实验在 20 和 50 kg/m ^{2的质量速度下进行}s 和 0.97 至 1.3°C 的壁过热度。获得的数据显示传热系数对热通量密度和质量速度没有显着依赖性，并且蒸汽质量超过 0.75 时传热显着恶化。在这些条件下，最可能的传热机制是在存在液-汽-壁接触线的情况下，由毛细力弯曲的薄液膜蒸发过程中传热的决定性影响。这是由一个模型计算得出的，该模型同时考虑了两相强制对流、允许抑制沸腾的核沸腾以及存在接触线时液​​膜的蒸发。