Abstract:

Experiments were performed to evaluate the micro-scale flow boiling heat transfer characteristics of acetone flowing through triangular silicon microchannels.The liquid-vapor two-phase flow pattern was visualized，along with simultaneous measurement of pressure and temperature.Periodical convective boiling heat transfer in a time scale of milliseconds was found.A full cycle can be subdivided into three sub-stages：liquid refilling stage，bubble nucleation，growth，coalescence and explosion stage，and transient liquid film evaporation stage.The flow field visualization showed that four liquid-vapor two-phase flow patterns appeared in microchannels，and the boiling incipience was identified.The effect of mass quality（x）on boiling heat transfer coefficient was analyzed.It was shown that under the conditions of the present study，when x <0.4，nucleate boiling was dominant，whereas when x >0.4，the forced convective boiling was dominant.

摘要：

以丙酮为工质，在三角形截面的硅基微通道内进行了微尺度沸腾传热实验研究。在对汽液两相流流型进行光学可视化测量的同时，对压力、温度等信号进行了同步动态测量。发现了周期在毫秒级的微时间尺度的周期性沸腾传热。1个完整的周期可以分成3个子过程：进液阶段，汽泡核化、增长、聚合及爆炸阶段，瞬变液膜蒸发阶段。总结出1个完整周期内所存在的4种汽液两相流流型。鉴别出了沸腾起始点。分析了沸腾传热系数随干度的变化关系，结果表明在本实验工况下：当干度小于0.4时，起主导作用的传热机制为核态沸腾；而当干度大于0.4时，起主导作用的传热机制为强制对流沸腾。