【摘要】 针对管状煤基炭膜气隙式膜蒸馏过程通量低的问题,进行膜蒸馏氯化钠溶液气液两相流强化实验及CFD模拟研究,探讨两相流流型和气含率对强化过程的影响。实验结果表明:N2流量对渗透通量影响的模拟结果与实验结果吻合较好。当进料流量为40 L×hh^-1、N2流量为50 L×h^-1 （气含率0.56）时,对应团状流,此时强化传质效果最好。模拟结果中强化过程的膜壁剪应力(约1.77 N×m^-2)明显大于无强化过程(约0.015 N×m^-2)。流动方向上,经强化后大小与方向均变化的剪应力可增强对料液的扰动进而增大渗透通量,也可降低膜污染与浓度极化程度进而延长操作时间。气含率不大于0.56b （泡状流、塞状流与团状流）时,随着气含率增大,气泡群对料液的扰动作用增强,强化传质效果变好;气含率大于0.56 （乳沫流与环状流）后,两相间出现较为明显且稳定的界面,扰动作用相比团状流时变差。利用CFD方法模拟得到的膜壁剪应力、气液两相流型、速度分布、湍流强度规律可用于定性分析两相流强化过程,为进一步探究该过程强化传质机理提供依据。更多还原

【Abstract】 Gas-liquid two-phase flow intensified air gap membrane distillation was investigated to increase permeation flux for desalination. A coal-based tubular carbon membrane was selected as the separation membrane. Sodium chloride solution was used as simulated sea water and nitrogen gas（N2） was used as the intensifying medium. Effects of two-phase flow parameters including flow pattern and gas holdup on process were evaluated. CFD simulation results of permeation flux variation with N2 flow rate show good agreements with experimental results. When the feed flow rate is 40 L×h^-1 and N2 flow rate is 50 L×h^-1（corresponding to 0.56 of gas holdup）, the optimal intensifying effect of mass transfer can be reached with slug flow state being achieved. Average wall shear stress is 1.77 N×m^-2 after intensification, which is greater than 0.015 N×m^-2 before intensification. Disturbance due to stress magnitude and direction variation by intensification can enhance permeation flux, reduce membrane fouling and decrease concentration polarization to prolong membrane usage duration. When the gas holdup is ≤ 0.56（bubble, plug and slug flow patterns）, disturbance by bubble clusters on fluid can be intensified, which results in better mass transfer. When the gas holdup is over 0.56（churn and annular flow patterns）, stable interface appeared that leads to less disturbance. Wall shear stress, gas-liquid flow pattern and velocity distribution can be used to quantitatively analyze two-phase flow intensification mechanism.更多还原