振动特性对中空纤维膜组件管外传质的影响

Effect of vibration characteristics on shell-side mass transfer in hollow fiber modules

为提高中空纤维膜组件的传质效率,减轻浓差极化,运用计算流体力学软件Fluent动网格技术,以含氧水的除氧过程为研究对象,研究了振动特性对中空纤维膜组件管外传质的影响。研究结果表明:与静止的工况相比,振动能够使流体产生二次流,使得流动从层流转化为紊流,增强流体与膜组件以及中空纤维管壁面的碰撞,极大程度地减轻浓差极化现象,进而强化传质;随着振动频率和振幅的增大,膜组件出口处氧质量浓度降低,水中氧的清除率增大,传质效果变好;一定条件下振动工况比静止工况氧的清除率最高可以提高144%,固定振幅为6 mm振动频率从2.5 Hz增加到10 Hz时清除率提高76%;固定频率为2.5 Hz振幅由2 mm增加到6 mm时清除率提高10%,增大振动频率对于强化传质的效果要好于增大振幅。研究结果可以为实际的工程应用提供理论指导。

In order to improve the mass transfer efficiency of hollow fiber modules and reduce the concentration polarization,the dynamic mesh of computational fluid dynamics software Fluent was used to study the characteristics of flow and mass transfer of a vibrating hollow fiber membrane module,and the effect of different vibration parameters on mass transfer performance was analyzed based on the process of removing oxygen from water.The numerical results show that vibration can cause secondary flow and the transition from laminar to turbulent flow, both of which enhance the collision between the fluid and the hollow fiber module and reduce the concentration polarization.So vibration is favorable to mass transfer enhancement.With the growth of vibration frequency and amplitude,the clearance rate of oxygen increases and the mass transfer performance gets better,whereas the outlet oxygen mass concentration decreases.Oxygen removal rate can be increased by 144% under a given vibration condition compared to no vibration.Oxygen removal rate is increased by 76% with the vibration frequency increased from 2.5 Hz to 10 Hz when the vibration amplitude is 6 mm,while it is only increased by 10%with the vibration amplitude increased from 2 mm to 6 mm when the vibration frequency is 2.5 Hz.Increasing the vibration frequency is more effective on the mass transfer enhancement than increasing the vibration amplitude.The results provide the theoretical guidance for practical engineering applications.