Abstract
The two-phase flow maldistribution phenomenon in microchannels with multi-parallel branches is inevitable in almost all common conditions, and not only affects the performance of the facility but also increases the risk of system instability. In order to better understand the distribution mechanism and to explore a potential strategy to improve uniformity, the pressure evolutions under different split modes in a microchannel with multi-parallel branches, were analyzed numerically. The results show that the fluctuations of transient pressure exhibit similar trends at various split modes, but the time-averaged pressure drops in the branches are very different. This may be related to the maldistribution of mass flow. Thus, the outlet pressures of the branches are numerically changed to explore the relationship between differential pressure and flow distribution. From this study, the flow distribution is seen to display a strong sensitivity to the branch differential pressure. By changing the pressure conditions, the gas flow of the middle branch can be effectively prevented from the main channel, and the flow type in this branch turns from gas-liquid to a single liquid phase. When the differential pressure of the first branch channel changes, the maldistribution phenomenon of the model can be mitigated to a certain extent. Based on this, by adjusting the differential pressures of the second branch, the maldistribution phenomenon can be further mitigated, and the normalized standard deviation (NSTD) decreases from 0.52 to approximately 0.26. The results and conclusions are useful in understanding the two-phase flow distribution mechanism and for seeking optimizing strategies.
概要
目的
几乎在所有常见条件下, 平行微通道都不可避免的出现两相流分布不均的现象。该现象不仅会影响设备的性能, 而且增加了系统不稳定性的风险。本文旨在从压力分布的角度探索改善平行微通道流动分布均匀性的策略, 并对平行微通道段塞流的分裂机制进行研究。
创新点
1. 对平行微通道内的段塞流流动分裂过程进行数值模拟, 成功复现了不同的分裂模式;2. 通过改变平行微通道的压力分布成功改善其流动分布不均现象。
方法
1. 通过数值模拟得到了不同分裂模式下平行微通道内部的压力演变过程(图5~7);2.通过改变平行微通道出口压力条件改善其流动分布不均现象(图10和11)。
结论
1. 随着平行微通道内气弹的运动和分裂, 通道内的压力呈周期性变化趋势, 对于不同的气弹分裂模式, 压力变化基本相同;2. 平行微通道内的流动分布对支管压差表现出强烈的敏感性;3. 通过改变压力条件可以改善平行微通道的流动分布不均现象。
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This work is supported by the National Natural Science Foundation of China (No. 51976181).
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Yu-qi HUANG designed the research. Peng-fei ZHANG processed the corresponding data and wrote the first draft of the manuscript. Yong-jun HUA helped to organize the manuscript. Xiang-guo XU revised and edited the manuscript.
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Peng-fei ZHANG, Xiang-guo XU, Yong-jun HUA, and Yu-qi HUANG declare that they have no conflict of interest.
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Zhang, Pf., Xu, Xg., Hua, Yj. et al. Effects of the outlet pressure on two-phase slug flow distribution uniformity in a multi-branch microchannel. J. Zhejiang Univ. Sci. A 23, 68–82 (2022). https://doi.org/10.1631/jzus.A2100135
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DOI: https://doi.org/10.1631/jzus.A2100135