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N_coal>0.2时,气泡聚并能够增强换热; 反之,当N_coal<0.2时,气泡聚并则会减弱换热。

This study experimentally investigated the effects of bubble coalescence on nucleate pool boiling. A micro heater array was used to generate vapor bubbles in FC-72 liquid with constant surface temperature boundary conditions while the heat flux at selected locations was measured using a high speed data acquisition system. The heat flux for boiling with coalescence was found to fluctuate much more than when only a single bubble formed on the surface due to the vaporization of the liquid layer trapped between the bubbles and oscillation of the bubbles after coalescence. These oscillations significantly increased the average heat transfer by increasing the frequency of rewetting of the heated surfaces compared to single bubble nucleation. The observations also showed that very fast coalescence events were not accompanied by an increase in the heat transfer rate as the liquid layer between the bubbles was physically pushed away by the rapid bubble growth during the inertial bubble growth stage instead of evaporating. The results show that the heat transfer increases for the dimensionless coalescence number, N_coal, more than 0.2 but decreases for N_coal less than 0.2.