微通道换热器（MCHX）集管中的制冷剂分配不当可能会使MCHX的容量降低30%，因为它会在蒸发器模式下产生不需要的过热区域，其中的传热比两相区域低得多。尽管制冷剂分配不均主要是由于集管内蒸汽和液体的相分离造成的，但它也受到集管内压降的影响。本研究的目的是根据实验结果建立预测集管内两相压降的关联式，以便将其纳入MCHX模型。两相R134a通过底部通道中的多个平行微通道管循环进入透明垂直集管，并通过顶部通道中的多个平行微通道管流出，代表可逆系统热泵模式下的流动。 测量了相邻两个微通道管之间的局部压降。根据实验结果，提出了一个预测集管内整体两相压降的模型。除了采用Zivi（1964）的含气率关联式和两相加速和重力压降的均质模型，以及Lockhart Martinelli（1949）的两相摩擦压降关联式外，该模型还将由于管道突出而产生的两相微小压降与单相蒸汽微小压降与两相倍增器相关联，在此之前的研究中开发并验证了单相蒸汽微小压降相关性。引用:ASHRAE论文:2015年ASHRAE年会，佐治亚州亚特兰大

Refrigerant maldistribution in the header of microchannel heat exchanger (MCHX) may reduce MCHX capacity by up to 30% because it creates the unwanted superheated region in the evaporator mode, where the heat transfer is much lower than the two-phase region. Although refrigerant maldistribution is mainly caused by phase separation of vapor and liquid in the header, it is also affected by the pressure drop in the header. The objective of this study is to develop the correlations for predicting two-phase pressure drop in the header based on experimental results, so they can be incorporated into MCHX model. Two-phase R134a is circulated into the transparent vertical header through multi-parallel microchannel tubes in the bottom pass and exits through multi-parallel microchannel tubes in the top pass representing the flow in heat pump mode of a reversible system. The local pressure drop between each two neighboring microchannel tubes is measured. Based on the experimental results, a model is proposed to predict the overall two-phase pressure drop in the header. Besides adopting the Zivi (1964) void fraction correlation and homogeneous model for two-phase acceleration and gravitation pressure drops as well as Lockhart-Martinelli (1949) correlation for two-phase friction pressure drop, the model relates the two-phase minor pressure drop due to tube protrusion with the single-phase vapor minor pressure drop with a two-phase multiplier, where the single-phase vapor minor pressure drop correlation was developed and validated in previous studies.