Numerical Investigation of Bubble Condensation of Subcooled Boiling in Narrow Rectangular Channels
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摘要: 建立过冷流动沸腾汽泡凝结质量及能量传递模型,采用流体体积法(VOF)多相流模型,对汽泡凝结过程进行数值模拟。模拟结果与相应条件下的实验结果吻合较好,误差在±20%之内,能够反映真实参数变化过程。根据模拟结果分析汽泡初始尺寸、过冷度和系统压力等因素对汽泡凝结行为的影响。结果表明:汽泡凝结时间与汽泡初始尺寸成正比;随着过冷度增加,汽泡凝结时间将大幅减少;汽泡凝结过程中,汽泡周围会出现旋涡,过冷度越高,旋涡越强烈;在过冷度较高时,汽泡内部也会出现旋涡;随着流道内压力升高,汽泡在过冷流体中的存活时间将大大增加。Abstract: The bubble condensation mass and energy transfer models for the subcooled boiling bubbles are developed,and the condensation progress for the bubbles is numerically simulated by VOF multiphase model.The simulation results agree well within ± 20% of the experiment results,which can reflect the real changing history of the parameters.Based on the simulation results,the effect of the initial bubble size,sub-cooling degree and system pressure on the bubble condensation behavior is analyzed.The analysis results show that the bubble lifetime in condensation is proportional to the bubble initial size;with the increasing of subcooling degree,the bubble lifetime will significantly reduce;vortex occurs at the region around the bubble,the higher the subcooling degree,the more intensive the vortex;vortex occurs also within the bubble in high subcooling degree boiling flow;and the bubble lifetime will be prolonged at higher system pressures in narrow rectangular channels.
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