This paper presents the refrigerant adiabatic upward flow in the vertical header of microchannel heat exchanger and its effect on distribution. R410A is circulated into the header through the microchannel tubes (5 or 10 tubes) in the bottom pass and exits through tubes (5 or 10 tubes) in the top pass representing flow in the heat pump mode of reversible systems. Three circular headers were explored, each with the microchannel tubes inserted to half depth. The quality was typically varied from 0.2 to 0.8. Mass flow rate was from 1.5 to 4.5 kg/h per microchannel. The best distribution is found at high flow rate and low quality. Distribution is improved by doubling the number of microchannel tubes although elongation of the header has negative effect. Visualization reveals the effects of flow patterns in terms of homogeneity and liquid momentum. Refrigerant in the churn flow has better distribution than in the separated flow since the two-phase mixture is more homogeneous. The distribution is better at high mass flux in the header because the higher momentum liquid can be supplied to the top exit tubes.
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机译：本文介绍了微通道换热器垂直集管中的制冷剂绝热向上流动及其对分布的影响。 R410A通过底部通道中的微通道管（5或10个管）循环进入集管，并通过顶部通道中的管（5或10个管）离开，代表可逆系统的热泵模式下的流量。探索了三个圆形集管，每个集管都将微通道管插入了一半的深度。质量通常在0.2到0.8之间变化。每个微通道的质量流速为1.5至4.5 kg / h。最好的分布是在高流速和低质量的情况下。尽管集管的伸长会产生负面影响，但通过使微通道管的数量增加一倍，可以改善分布。可视化揭示了均匀性和液体动量方面的流动模式的影响。由于两相混合物更均匀，搅动流中的制冷剂比分离流中的制冷剂分布更好。集管中的质量流量较高时，分布会更好，因为可以将较高动量的液体供应到顶部出口管。
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