Abstract Two-phase oil-water pipe flow is common in oil production and transportation. Appropriate estimation of phase wetting (oil wet or water wet) of internal pipe walls can significantly reduce corrosion control costs, and increase confidence in measures taken to ensure the integrity of pipelines. Water wetting can be avoided by fully dispersing the water phase into the oil phase. It has been suggested that pipe wettability may affect oil-water flow patterns; particularly, water-in-oil dispersed flow transition boundaries. However, there are no systematic studies in the literature on this matter for carbon steel pipes, which are the preferable choice for economic reasons in the oil and gas industry. Moreover, traditional and widely used models to predict the onset of dispersed flow do not consider the effect of pipe wettability. This work studies phase wetting and water layer thickness in large scale oil-dominated oil-water horizontal flow in carbon steel and PVC pipes of similar internal diameter (0.1 m) and roughness, but different wettability. The effect of wetting hysteresis (oil or water pre-wetted pipe surface) on phase wetting is also investigated. It is demonstrated that pipe wettability plays a very important role on the transition boundaries for phase wetting (oil wet to water wet) and the transition to fully dispersed flow. Water droplet deposition and spreading are identified as the main mechanisms for incipient segregation in a hydrophilic pipe. In a hydrophobic pipe, poor surface wettability hinders the sticking and spreading of water droplets. Water wetting in a hydrophobic pipe requires a sufficient low flow velocity at which local droplet accumulation and coalescence becomes the dominant segregation mechanism. Predictions from available hydrodynamic models are compared with the experimental results and recommendations are provided.

中文翻译：

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不同润湿性水平管油水流中水润湿及水层厚度研究

摘要 油水两相管流在石油生产和运输中很常见。适当估计内管壁的相润湿（油湿或水湿）可以显着降低腐蚀控制成本，并增加对确保管道完整性所采取措施的信心。通过将水相完全分散到油相中可以避免水润湿。有人提出管道润湿性可能会影响油水流动模式；特别是油包水分散流过渡边界。然而，对于碳钢管，在石油和天然气行业中，出于经济原因，碳钢管是优选的选择，在这方面的文献中并没有系统的研究。此外，用于预测分散流开始的传统和广泛使用的模型没有考虑管道润湿性的影响。本工作研究了内径（0.1 m）和粗糙度相似但润湿性不同的碳钢和PVC管道中大型油主导油水水平流中的相润湿和水层厚度。还研究了润湿滞后（油或水预润湿管表面）对相润湿的影响。结果表明，管道润湿性在相润湿（油湿到水湿）的过渡边界和向完全分散流的过渡中起着非常重要的作用。水滴沉积和扩散被认为是亲水管道中初期分离的主要机制。在疏水管中，较差的表面润湿性阻碍了水滴的粘附和扩散。疏水管中的水润湿需要足够低的流速，此时局部液滴积累和聚结成为主要的分离机制。将可用流体动力学模型的预测与实验结果进行比较并提供建议。