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.

Key words: Two-phase flow; Multi-parallel microchannel; Flow distribution; Slug flow; Split modes

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