Abstract This paper presents a detailed discussion on the hysteresis phenomenon caught during the flow boiling heat transfer of R245fa on a Carbon/Carbon surface. Due to the partial hydrophilicity of the Carbon/Carbon surface, a hysteresis in flow boiling heat transfer is observed and studied to understand the underlining heat transfer mechanisms on the basis of the surface activation. A combined experimental approach is developed by monitoring the local wall temperature and contemporarily recording the two-phase flow patterns using a high-speed video camera. The observed dewetting/rewetting phenomenon is linked to the activation process of the Carbon/Carbon surfaces giving new insights on the boiling behavior of hydrophilic surfaces. The results show that after activation the heat transfer coefficients increases up to 20%. The experimental results are compared against the estimations of a model recently proposed by the present Authors and based on R134a measurements. The proposed model is able to predict the heat transfer coefficients within ±20%.

中文翻译：

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亲水性碳/碳表面流动沸腾传热过程中的滞后现象

摘要 本文详细讨论了在碳/碳表面上 R245fa 流动沸腾传热过程中捕获的滞后现象。由于碳/碳表面的部分亲水性，观察和研究了流动沸腾传热的滞后现象，以了解基于表面活化的基本传热机制。通过监测局部壁温并同时使用高速摄像机记录两相流动模式，开发了一种组合实验方法。观察到的去湿/再润湿现象与碳/碳表面的活化过程有关，为亲水表面的沸腾行为提供了新的见解。结果表明，活化后传热系数增加了20%。将实验结果与本作者最近提出的基于 R134a 测量值的模型估计值进行比较。所提出的模型能够在±20% 内预测传热系数。