中文摘要：

在低质量流速和高热流密度下，对复杂结构微流体芯片中的流动沸腾进行了瞬态流型研究，发现了毫秒级微时间尺度的周期性流型和微通道中的分层流。在单个微通道区域，液膜沿流动方向逐渐增厚且蒸干总是首先发生在其上游区域，而在不同微通道区域间，下游微通道首先蒸干。分析表明，液相弗劳德数（Froude number）较低是微通道中分层流存在的原因。高沸腾数（Boiling number）引起汽液界面较大的剪切应力从而使液体不断向微通道出口处聚集，引起液膜厚度沿流动方向逐渐增厚。

英文摘要：

The transient flow patterns of boiling in a microfluidic chip with complicated microstructures were studied at low mass fluxes and high heat fluxes. The periodic flow pattern in the timescale of milliseconds and stratified flow pattern were identified. For a microchannel in a separated zone, the liquid film thickness is increased along the flow direction and the dry-out always occurs earlier at the microchannel upstream. However, for different microchannel zones, the dry-out takes place earlier in the downstream zone. It is analyzed that the low liquid Froude number is responsible for the stratified flow. The high boiling number results in large shear stress on the vapor-liquid interface, leading to the accumulation of the liquid in the microchannel downstream. This causes the increased liquid film thickness along the flow direction.