通气强化气隙式膜蒸馏质量传递数值模拟  

Numerical simulation of mass transfer during gas injected air gap membrane distillation

作　　者：李花[1] 潘艳秋[1] 俞路[1] 何德民[1] LI Hua;PAN Yan-qiu;YU Lu;HE De-min(School of Chemical Engineering,Dalian University of Technology,Dalian 116024,China)

机构地区：[1]大连理工大学化工学院

出　　处：《高校化学工程学报》2019年第4期824-831,共8页Journal of Chemical Engineering of Chinese Universities

基　　金：中央高校基本业务费项目(DUT17JC07)

摘　　要：采用计算流体动力学(CFD)方法对通气强化气隙式膜蒸馏(AGMD)过程进行了数值模拟,并探讨了强化过程的传质机理。利用FLUENT软件结合流体体积函数(VOF)模型,以通气强化过程膜管内的气液两相流体为研究对象,设定氯化钠溶液为分离介质,氮气为强化介质进行模型建立与模拟分析。结果表明:渗透通量模拟数据与实验数据基本吻合;通气可增大渗透通量(J)与传质系数(k),降低浓度极化率(CPC),有利于膜蒸馏过程;浓度分布模拟结果可用于预测局部浓度极化程度;由拟合出的通气强化过程传质系数关联式的形式,可知过渡扩散-泊肃叶流传质机理比过渡扩散传质机理更接近于通气强化膜蒸馏真实传质过程。基于气体在多孔介质中的传质理论,通过合理建模并设定模拟参数,可研究通气强化传质过程的影响因素(文中为气含率)对强化效果的影响,该方法也可推广应用于研究多影响因素的膜蒸馏强化传质过程。Numerical simulation of mass transfer during gas injected air gap membrane distillation was studied by computational fluid dynamic(CFD) and the intensification mechanism was discussed. Gas-liquid two-phase flow in membrane tubes was used as the object and simulation was performed with FLUENT software based on volume of fluid(VOF) model. Sodium chloride aqueous solution was employed as the separation medium and nitrogen gas as the intensifying medium. The results show that the simulated permeation flux data are consistent with the experimental data. Gas injection is beneficial to membrane distillation processes, which can increase permeation flux(J) and mass transfer coefficient(k), and decrease concentration polarization coefficient(CPC). Simulated sodium chloride concentration distribution can be used to predict local concentration polarization effects. According to the mass transfer coefficient correlations, the Knudsen-Molecular diffusion-Poiseuille flow transition mechanism is better matched with the real mass transfer process than Knudsen-molecular diffusion mechanism. Affecting factors(i.e. gas holdup) of intensification can be studied by reasonable modeling and setting of simulation parameters. This method can also be applied to study enhanced membrane distillation mass transfer processes with multi-factors.

关 键 词：膜蒸馏 两相流 过程强化 传质系数 计算流体动力学 

分 类 号：TQ465.92[化学工程—制药化工]