Abstract:

The influences of aerator aperture size and aeration rate on the gas hold-up, liquid circulation velocity, wall shear stress and turbulence intensity in a novel airlift ceramic membrane filtration equipment containing a 19-channel ceramic membrane was investigated by the CFD simulation. Further, the VOF model was adopted to simulate the flow state of the gas-liquid two-phase fluid and the mean error between experiment date and simulation date was 5%-10%. The results demonstrated that the gas hold-up increased with increasing aeration rate and decreasing aerator aperture size. The liquid circulation velocity, wall shear stress and turbulence intensity increased with increasing aeration rate, and the increasing trend became slow after the aeration rate reached 400 L·h^-1. For the three aperture aerator with different size, the comparison of experiment and simulation results have indicated that the liquid circulation velocity was only related to the aeration rate, and had little to do with aerator aperture size. Decreasing of the aerator aperture size was conductive to the increasing of the wall shear stress and the filtration process.

Key words: airlift, ceramic membrane, computational fluid dynamics, VOF, two-phase flow, simulation

摘要：

采用VOF双流体模型对19通道气升式陶瓷膜过滤装置进行气液两相流的流体动力学模拟,研究了曝气孔直径和曝气量对气升式陶瓷膜过滤装置的气含率、环流液速、膜面剪切力及膜管内湍流强度的影响,模拟结果与实验结果的误差在5%~10%之间。结果表明,气升管与降液管的气含率都随曝气量增大而增大,随曝气孔直径减小而增大;环流液速、膜面剪切力及膜管内的湍流强度都随曝气量增大先增大,当曝气量达到400L·h^-1时其增大趋势变缓。通过实验和模拟比较了3种不同孔径的曝气头,环流液速与曝气孔的直径关系不大,仅与曝气量相关,但曝气孔直径越小,其膜面剪切力越大,越有利于过滤过程的进行。

关键词: 气升式, 陶瓷膜, 计算流体力学, VOF方法, 两相流, 模拟