Experimental and theoretical study on liquid film thickness of upward annular flow in helically coiled tubes

IF 3.6 2区工程技术 Q1 MECHANICS International Journal of Multiphase Flow Pub Date : 2024-10-25 DOI:10.1016/j.ijmultiphaseflow.2024.105041

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Abstract

The liquid film thickness is crucial for studying the thermal hydraulic mechanism of the annular flow region in helically coiled tubes (HCTs). This paper introduces a refined experimental study on the liquid film thickness of annular flow in HCTs, utilizing a newly developed liquid film sensor. The experimental results indicate that the smaller coil diameters and pitches result in thinner average liquid film thicknesses. The average liquid film thickness decreases with increasing superficial gas velocity and decreasing superficial liquid velocity. However, the liquid film thickness at different circumferential positions on the cross-section of the tube exhibits varying sensitivities to superficial gas and liquid velocities. The experimental data reveal that the existing typical correlation formula for the average liquid film thickness of annular flow in straight tubes does not apply to HCTs. Consequently, a new prediction model is proposed for the average liquid film thickness of the annular flow region in HCTs, based on the modified Froude number, modified Dean number, Ekman number, and Reynolds number. This model comprehensively incorporates the structural characteristics of HCTs and fluid properties, and its validity is verified through the utilization of available and current data in the literature.

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螺旋卷管内上升环流液膜厚度的实验和理论研究

液膜厚度对于研究螺旋卷管（HCT）环流区的热液压机制至关重要。本文介绍了利用新开发的液膜传感器对 HCT 环流液膜厚度进行的精细实验研究。实验结果表明，线圈直径和间距越小，平均液膜厚度越薄。平均液膜厚度随着表层气体速度的增加和表层液体速度的减小而减小。然而，管横截面上不同圆周位置的液膜厚度对表层气体和液体速度的敏感性各不相同。实验数据表明，现有的直管环流平均液膜厚度典型相关公式不适用于 HCT。因此，基于修正的弗劳德数、修正的迪恩数、埃克曼数和雷诺数，提出了一种新的 HCT 环流区平均液膜厚度预测模型。该模型综合考虑了 HCT 的结构特征和流体特性，并通过利用现有文献数据验证了其有效性。

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来源期刊

International Journal of Multiphase Flow 物理-力学

CiteScore

7.30

自引率

10.50%

发文量

244

审稿时长

4 months

期刊介绍： The International Journal of Multiphase Flow publishes analytical, numerical and experimental articles of lasting interest. The scope of the journal includes all aspects of mass, momentum and energy exchange phenomena among different phases such as occur in disperse flows, gas–liquid and liquid–liquid flows, flows in porous media, boiling, granular flows and others. The journal publishes full papers, brief communications and conference announcements.