Abstract
A performance simulator of spiral wound membrane (SWM) modules used for desalination is a valuable tool for process design and optimization. The existing state-of-the-art mesoscale simulation tools account for the spatial non-uniformities created by the operation itself (flow, pressure, and concentration distributions) but they assume uniform membrane properties. However, experimental studies reveal that membrane properties are by no means uniform. Therefore, the need arises to account for this non-uniformity in simulation tools thus enabling a systematic assessment of its impact, among other benefits; a first step toward this goal is presented herein. In particular, the issue of an organic fouling layer growing on a membrane with non-uniform permeability is analyzed. Several mathematical treatments of the problem are discussed and indicative results are presented. The concept of fouling layer thickness probability density function is suggested as a means to introduce sub-grid level calculations in existing simulation tools. The analysis leads to the selection of an appropriate methodology to incorporate this effect in the dynamic simulation of fouling layer evolution at the membrane-sheet scale.
Highlights
The spiral wound membrane (SWM) modules have been established in reverse osmosis desalination as well as in water treatment and other applications due to their elegant design and their capability of achieving efficient performance with modest energy consumption
This study deals with the problem of evolution of organic fouling layer spatial non-uniformity during operation of spiral wound desalination-membrane modules
Two types of non-uniformities are considered; i.e., topological and non-topological. The latter can be simulated through the use of probability density functions
Summary
The spiral wound membrane (SWM) modules have been established in reverse osmosis desalination as well as in water treatment and other applications due to their elegant design and their capability of achieving efficient performance with modest energy consumption. The use of harmonic functions, as the one employed here, to represent non-uniform property or geometry variation is typical in science and engineering literature [21] This treatment is focused on the evolution of non-uniformity of H; the evolution of the ratio H/Hm (where Hm is the average film thickness) is shown in Figures 2 and 3 for operation under constant pressure and constant flux, respectively. In both cases the initial profile of H is similar to that of K. 3. Evolution of fouling layer thickness profile for a cosine variation of membrane permeability (β = 1, constant pressure operation). Problem Formulation for the Evolution of Thickness Probability Density Function
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