宽矩形硅微通道中流动冷凝的流型

Flow pattern of condensation in wide rectangular silicon microchannels

对水力直径90.6μm、宽深比9.668的矩形硅微通道中的流动冷凝过程进行了可视化研究。研究发现,宽矩形硅微通道中的冷凝,沿程主要有珠状-环状复合流、喷射流和弹状-泡状流等流型。在珠状-环状复合流区,冷凝液膜可覆盖通道竖直侧壁,而在通道长边上,仍然为珠状凝结。喷射流位置随着入口蒸气Reynolds数的增大而延后,通道截面形状对流动冷凝不稳定性也存在很大影响。喷射流之后为弹状-泡状流,弹状气泡沿程逐渐缩短,并在表面张力的作用下收缩成圆球形气泡。冷凝通道的平均传热系数将随着入口蒸气Reynolds数的增大而增大。

Visualization experiments were conducted to study the condensation flow in rectangular silicon microchannels with hydraulic diameter of 90.6 μm and width/depth ratio of 9. 668. In such wide rectangular microchannels, droplet-annular compound flow, injection flow and slug-bubbly flow were observed. In the droplet-annular compound flow regime, the vertical wall of the channel was completely covered by the condensate film. But on the long sidewall of the channel, droplet condensation still existed. The occurrence of injection flow would be postponed with increasing inlet vapor Reynolds number. And it was confirmed that the cross-section shape of the microchannel had a significant effect on the instability of condensation flow. Slug-bubbly flow occurred after injection flow. Along the condensation stream, the slug would contract into round bubble due to surface tension. The average heat transfer coefficient of the channel increased with increasing inlet vapor Reynolds number.