受限微细通道内的流动沸腾流型转化准则

理论分析了微细尺度条件下通道尺寸对气泡运动特性的影响,指出当通道尺寸小于气泡脱离直径时一种特殊流型"受限泡状流"的产生及其特性。对受限通道内流动沸腾过程中的流型转变准则进行了推导,绘制了相应的流型图,并进行了实验验证。研究表明,微细通道内沸腾流动气液两相流流型转变比绝热工况下有明显的推迟;而在流动沸腾工况、相同热通量和质量流速条件下,随着微细通道尺寸的减小,流型转化会在一定程度上提前产生。

Flow pattern transition criteria of flow boiling in confined mini/micro-channel

The effect of channel size on bubble motion characteristics under mini/micro-scale condition is analyzed theoretically.The comparison between channel width and bubble departure diameter indicate that when the former is smaller than the latter, the flow pattern of confined bubbly flow will occur, the flow features of which is further analyzed.On this basis, traditional flow patterns in confined mini/micro-channel are subdivided and flow pattern transition criteria are derived.The prediction of the theoretical model agrees well with corresponding experimental data.The analysis on characteristics of the transition criteria shows an apparent postponement of transition for flow boiling in mini/micro-channel than that under adiabatic conditions.Moreover, for flow boiling under the same heat flux and mass flux conditions, the flow pattern transition may occur earlier with the decrease of channel size.