竖直提升管内气泡运动状态数值模拟研究

Numerical simulation of the bubble motion in the vertical riser

在Einstein制冷循环系统中,气泡泵竖直提升管内为弹状流时效率较高。选取VOF(流体体积函数)模型对其管内气泡的运动状态进行计算流体力学数值模拟。结果表明:当过热度恒定时,随着压力增加,单个气泡的生成时间延长且体积变小,但气泡均匀性提高;当压力恒定时,随着过热度增大,气泡生成速率加快,融合体积增大,易于形成系统所需的弹状流。因此,在Einstein制冷循环系统中,在压力为0.4 MPa的工况下,需采取较高的过热度才能保证气泡泵的正常运转;与水相比,氨水溶液更适合作为气泡泵工质。

The formation of slug flow in the vertical riser will lead to higher efficiency of bubble pump in the Einstein refrigeration cycle system.In this paper,the numerical simulation on the state of the bubbles in a vertical riser of the bubble pump was performed by volume of fluid(VOF)model.The results showed that at the constant degree of superheat,the duration of single bubble formation was prolonged,and its volume become smaller.But the bubble uniformity was enhanced when the working pressure increased.However,at the constant working pressure,the bubble generation rate and the fusion volume of the bubbles increased with the increased superheat temperatures.the required elastic flow formed easily.The following conclusions could be drawn that in the Einstein refrigeration cycle system with the pressure of 0.4 MPa,the higher superheat temperature should be adopted to ensure the normal operation of the bubble pump.And compared with the working fluid of water,the ammonia solution was more suitable for the bubble pump.