微圆柱阵微通道内沸腾换热及气泡运动特性研究

基于流体体积(VOF)模型对恒定热流密度下的微圆柱阵通道内的流动沸腾换热特性展开数值研究,并利用几何重构法捕捉气液两相界面迁移变化,研究了流道内流速的分布和微圆柱高度对气泡分布、沸腾换热性能及沸腾不稳定性的影响。结果表明:微圆柱的存在增加了气泡核化点密度;气泡运动增加了工质与加热壁面接触的可能性;微圆柱高度较低时,易发生气塞现象,加热面散热不均导致局部异常过热,换热性能下降;微圆柱阵通过阻碍气泡反向流动来降低沸腾不稳定性,但微圆柱高度过高会造成换热系统振荡,影响传热可靠性。

Study on Boiling Heat Transfer and Bubble Motion in Micro-channel of Micro-rib Array

The heat transfer characteristics of flow boiling in the cylindrical micro-fin channel with constant heat flux at the bottom were numerically studied,which was based on the VOF flow model coupled with boiling heat and mass transfer model.To capture the movement of vapor-liquid interface by the geo-reconstruction method,this article studied the partial velocity variation of two-phase interface.Simultaneously,it analyzed the effect of rib height on the morphology of bubbles,flow boiling heat transfer characteristics and boiling instability in the micro-channel.The results show that the presence of micro-columns increases the density of bubble nucleation point.The bubbles movement increases the possibility of contact between working medium and heating wall.When the height of rib is low,the capillary force generated by the secondary channel is weak and air bubbles are not easy to escape.This can lead to locally abnormal overheating and cause the heat transfer to deteriorate.Reversing flow of the bubbles is blocked by micro-fin array,and the boiling instability is reduced.However,over-hight micro-fin can lead to oscillate heat transfer system,thus affecting the reliability of heat transfer.