超声波场中蒸汽气泡凝结过程及传热特性

利用高速摄像仪记录有、无超声波时注入过冷水中蒸汽气泡的凝结过程,以分析超声波对蒸汽气泡凝结过程及传热特性的影响。结果表明:在超声波场中,蒸汽气泡表面会形成晶格状毛细波,有效增加气泡表面积,并加强气泡周围流体热边界层扰动,从而导致凝结换热的强化及气泡凝结速度加快。基于15～60 K过冷度下,有、无超声波时较大蒸汽气泡凝结的实验数据,拟合得出有、无超声波时的气泡凝结换热经验关联式,预测误差在±30%以内。

Condensation process and heat transfer of vapor bubbles in ultrasonic field

Condensation processes of vapor bubbles being injected into subcooled water with and without ultrasonic vibration were recorded by a high-speed video camera to analyze the effects of ultrasonic field on the condensation process and heat transfer of vapor bubbles. Experimental results indicated that the lattice shaped capillary wave formed on the bubble surface increased the condensation heat transfer area greatly and intensified the turbulence in the thermal boundary layer around the vapor bubble, enhancing condensation heat transfer and accelerating bubble condensation in the ultrasonic field. Based on experimental data of relatively large vapor bubbles at liquid subcooling of 15-60 K, empirical correlations were obtained for predicting the condensation heat transfer of vapor bubbles with and without ultrasonic, with deviations within ±30%.