垂直上升圆管内等温气泡流动的总体平衡建模

Population Balance Modelling of Isothermal Vertical Upward Bubbly Flow

对等温条件下垂直上升管内气泡的总体平衡(population balance)建模,提出了一种平均气泡数密度(ABND)方法.通过将平均气泡数密度传递方程引入到商业计算流体力学(CFD)软件ANSYS CFX10中来体现气泡的总体平衡.对湍流驱动下气泡自由碰撞以及湍流涡旋携带下撞击引起的气泡聚并和破裂效应采用Hibiki和Ishii提出的气泡聚并和破裂模型.对气泡流动中的基本变量:局部气含率和液体速度沿径向的分布进行了预测,并与Liu和Bankoff的实验数据进行了对比.预测结果和实测数据之间具有很好的一致性,证明了平均气泡数密度方法对气泡流动建模的适用性.

An averaged bubble number density （ABND） approach was proposed for modelling the population balance of bubbles in a vertical tube under isothermal condition. The population balance was realized by incorporating the ABND transport equation into a commercial computational fluid dynamics （CFD） code ANSYS CFX 10. The coalescence and breakage effects of the gas bubbles due to random collision and impact of turbulent eddies were modeled using the mechanistic model proposed by Hibiki and Ishii. Local radial distributions of void fraction and liquid velocity as the primitive variables in bubbly flow were predicted and compared with the experimental data by Liu and Bankoff. Close agreements between the predictions and measurements demonstrated the capability of the ABND approach in modeling bubbly flow conditions.