Rough or wiggly? Membrane topology and morphology for fouling control
Rough or wiggly? Membrane topology and morphology for fouling control
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DOI：
10.1017/jfm.2018.965
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发表时间：
2019-01-14
影响因子：
3.7
通讯作者：
Battiato, Ilenia
中科院分区：
文献类型：
--
作者：
Ling, Bowen;Battiato, Ilenia
在反渗透膜 (ROM) 过滤过程中，系统性能会受到膜污染的显着影响，导致渗透通量显着下降以及系统运行所需的能量输入增加。在这项工作中，我们开发了一个能够动态捕获污染物演变的模型，该模型将瞬态纳维-斯托克斯方程和平流扩散方程与污染物积累的吸附-解吸方程结合起来。该模型针对渗透通量的不稳定测量以及稳态空间污垢模式进行了验证。对于直通道，我们推导出 Sherwood 数和 Bejan 数之间的通用比例关系，即分别通过膜的无量纲渗透通量和沿通道的压降，并将该结果推广到经过形态和/或拓扑修改的膜，即其形状（摆动）或表面粗糙度从矩形和平面参考情况发生改变。我们证明，可以通过修改的雷诺数 Re* 和膜性能指数 xi 的定义来确定通用缩放比例，该雷诺数 Re* 解释了膜修改引入的额外长度比例，以及膜性能指数 xi ，这是相对于清洁渗透通量和操作系统所需的能量输入的总效率度量。我们的数值模拟表明，对于较小的 Re* 值，“摆动”膜的性能优于“粗糙”膜，而在较高 Re* 值时，趋势则相反。所提出的方法能够在同一框架下定量研究、优化和指导形态和拓扑改变的膜的设计，同时提供对控制整体系统性能的物理机制的见解。
During filtration in reverse osmosis membranes (ROM), the system performance is dramatically affected by membrane fouling which causes a significant decrease in permeate flux as well as an increase in the energy input required to operate the system. In this work, we develop a model, able to dynamically capture foulant evolution, that couples the transient Navier-Stokes and the advection-diffusion equations, with an adsorption-desorption equation for the foulant accumulation. The model is validated against unsteady measurements of permeate flux as well as steady-state spatial fouling patterns. For a straight channel, we derive a universal scaling relationship between the Sherwood and Bejan numbers, i.e. the dimensionless permeate flux through the membrane and the pressure drop along the channel, respectively, and generalize this result to membranes subject to morphological and/or topological modifications, i.e. whose shape (wiggliness) or surface roughness is altered from the rectangular and flat reference case. We demonstrate that a universal scaling can be identified through the definition of a modified Reynolds number, Re*, that accounts for the additional length scales introduced by the membrane modifications, and a membrane performance index, xi, an aggregate efficiency measure with respect to both clean permeate flux and energy input required to operate the system. Our numerical simulations demonstrate that 'wiggly' membranes outperform 'rough' membranes for smaller values of Re*, while the trend is reversed at higher Re*. The proposed approach is able to quantitatively investigate, optimize and guide the design of both morphologically and topologically altered membranes under the same framework, while providing insights into the physical mechanisms controlling the overall system performance.