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该文实验研究了气泡聚并对核态池沸腾换热的影响。在恒壁温的边界条件下,利用微加热器阵列加热液态FC-72产生气泡,同时利用高速数据采集系统测量特定区域的热流密度。由于气泡之间液体层的蒸发和气泡聚并后产生的振荡,沸腾过程中发生气泡聚并时热流密度的波动远强于加热表面仅有单气泡生成时的情形。与单气泡成核相比,气泡聚并所产生的振荡提高了加热表面的再润湿频率,从而显著增加了平均传热。观测还表明,由于气泡之间的液体层被仍处于惯性生长阶段的气泡推离,气泡聚并速度非常快时并不会伴随热流量的增加。实验结果表明:当无量纲的聚并数Ncoal>0.2时,气泡聚并能够增强换热;反之,当Ncoal<0.2时,气泡聚并则会减弱换热。
In this paper, the influence of bubble aggregation on the nucleate pool boiling heat transfer is experimentally studied. Under constant wall temperature boundary conditions, liquid fuel FC-72 was heated by a microheater array to generate bubbles, and a high-speed data acquisition system was used to measure the heat flux in a specific area. Due to the oscillation of the liquid layer between the bubbles and the oscillation that occurs after the bubbles are condensed, the fluctuation of the heat flux density at the time of bubble aggregation during boiling is much stronger than when only the single bubbles were formed on the heating surface. Compared with single-bubble nucleation, the oscillation caused by the bubble coalescence increases the rewetting frequency of the heated surface, thereby significantly increasing the average heat transfer. Observations also show that as the liquid layer between the bubbles is pushed away by the bubbles still in the inertial growth phase, the bubbles do not converge at very fast rates without an increase in heat flux. Experimental results show that when the dimensionless number of coalescence Ncoal> 0.2, the bubble coalescence can enhance the heat transfer; Conversely, when Ncoal <0.2, the bubble coalescence will reduce the heat transfer.