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Membranes
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Flow and Transport in Membranes: Modeling and Experimental Verification
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Flow and Transport in Membranes: Modeling and Experimental Verification

A special issue of Membranes (ISSN 2077-0375). This special issue belongs to the section "Membrane Physics and Theory".

Deadline for manuscript submissions: closed (20 February 2021) | Viewed by 10443

Special Issue Editor

Dr. Amgad Salama

E-Mail Website
Guest Editor
Process System Engineering, University of Regina, Regina, SK S4S 0A2, Canada
Interests: modeling separation processes using membrane technology; numerical methods; transport phenomena; capilaraity; CFD
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Modelling filtration processes using membrane technology confronts several difficulties with respect to establishing the appropriate framework. When the dispersals are solid particles, Hermia models stand as the most used models that explain fouling development using polymeric-type membranes. Four mechanisms have been proposed to describe the declining behaviour of permeation flux along the life span of the membrane. Three of these models are concerned with the early stage of membrane operation when its surface has not been fully covered with dispersals, and one mechanism for the later stage. Even though these three mechanisms work concurrently, only one of them is considered dominating the early-stage development of fouling. The determination of that dominant mechanism is, in fact, a matter of fitting exercise with experimental measurements. On the other hand, when the dispersals are fluids of immiscible nature with the continuous one, other framework needed to be adapted. Although some researchers considered extending Hermia models to encounter fluid emulsions, some others suggested additional mechanisms to the modelling of the separation of fluid emulsions using membrane technology. These include, for example, concentration polarization, and CFD investigation of microfiltration to highlight the different mechanisms that are involved in the filtration of fluid emulsions.

While modelling the filtration of emulsions using polymeric-type membranes has seen considerable advancement, less efforts have been spent to study filtration using ceramic-type membranes. This probably stems from the complexity of the internal pore structure of ceramic membranes compared with polymeric ones.

These and others highlight the importance of collecting opinions and research works on the advances that has been established and recent research works related to the modelling of filtration processes using membrane technology. Topics include, but are not limited to, modelling separation processes using polymeric- and/or ceramic-type membranes, CFD studies on macroscopic and microscopic filtration units, effects of surface affinity modification on the filtration processes, transport phenomena, fractal description of membranes, and experimental investigation of the filtration of different kinds of emulsions. Authors are invited to submit their latest results; both original papers and reviews are welcome.

Dr. Amgad Salama
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Membranes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Modeling
  • Ceramic-type membranes
  • Polymeric-type membranes
  • CFD analysis
  • Experimental validation
  • Fouling development

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Published Papers (3 papers)

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Research

24 pages, 3833 KiB  
Article
The Effect of the Oleophobicity Deterioration of a Membrane Surface on Its Rejection Capacity: A Computational Fluid Dynamics Study
by Amgad Salama, Adel Alyan, Mohamed El Amin, Shuyu Sun, Tao Zhang and Mohamed Zoubeik
Membranes 2021, 11(4), 253; https://doi.org/10.3390/membranes11040253 - 31 Mar 2021
Cited by 5 | Viewed by 2311
Abstract
In this work, the effects of the deteriorating affinity-related properties of membranes due to leaching and erosion on their rejection capacity were studied via computational fluid dynamics (CFD). The function of affinity-enhancing agents is to modify the wettability state of the surface of [...] Read more.
In this work, the effects of the deteriorating affinity-related properties of membranes due to leaching and erosion on their rejection capacity were studied via computational fluid dynamics (CFD). The function of affinity-enhancing agents is to modify the wettability state of the surface of a membrane for dispersed droplets. The wettability conditions can be identified by the contact angle a droplet makes with the surface of the membrane upon pinning. For the filtration of fluid emulsions, it is generally required that the surface of the membrane is nonwetting for the dispersed droplets such that the interfaces that are formed at the pore openings provide the membrane with a criterion for the rejection of dispersals. Since materials that make up the membrane do not necessarily possess the required affinity, it is customary to change it by adding affinity-enhancing agents to the base material forming the membrane. The bonding and stability of these materials can be compromised during the lifespan of a membrane due to leaching and erosion (in crossflow filtration), leading to a deterioration of the rejection capacity of the membrane. In order to investigate how a decrease in the contact angle can lead to the permeation of droplets that would otherwise get rejected, a CFD study was conducted. In the CFD study, a droplet was released in a crossflow field that involved a pore opening and the contact angle was considered to decrease with time as a consequence of the leaching of affinity-enhancing agents. The CFD analysis revealed that the decrease in the contact angle resulted in the droplet spreading over the surface more. Furthermore, the interface that was formed at the entrance of the pore opening flattened as the contact angle decreased, leading the interface to advance more inside the pore. The droplet continued to pass over the pore opening until the contact angle reached a certain value, at which point, the droplet became pinned at the pore opening. Full article
(This article belongs to the Special Issue Flow and Transport in Membranes: Modeling and Experimental Verification)
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23 pages, 5221 KiB  
Article
A Unified, One Fluid Model for the Drag of Fluid and Solid Dispersals by Permeate Flux towards a Membrane Surface
by Amgad Salama, Shuyu Sun and Tao Zhang
Membranes 2021, 11(2), 154; https://doi.org/10.3390/membranes11020154 - 22 Feb 2021
Cited by 1 | Viewed by 2169
Abstract
The drag of dispersals towards a membrane surface is a consequence of the filtration process. It also represents the first step towards the development of the problem of fouling. In order to combat membrane fouling, it is important to understand such drag mechanisms [...] Read more.
The drag of dispersals towards a membrane surface is a consequence of the filtration process. It also represents the first step towards the development of the problem of fouling. In order to combat membrane fouling, it is important to understand such drag mechanisms and provide a modeling framework. In this work, a new modeling and numerical approach is introduced that is based on a one-domain model in which both the dispersals and the surrounding fluid are dealt with as a fluid with heterogeneous property fields. Furthermore, because of the fact that the geometry of the object assumes axial symmetry and the configuration remains fixed, the location of the interface may be calculated using geometrical relationships. This alleviates the need to define an indicator function and solve a hyperbolic equation to update the configuration. Furthermore, this approach simplifies the calculations and significantly reduces the computational burden required otherwise if one incorporates a hyperbolic equation to track the interface. To simplify the calculations, we consider the motion of an extended cylindrical object. This allows a reduction in the dimensions of the problem to two, thereby reducing the computational burden without a loss of generality. Furthermore, for this particular case there exists an approximate analytical solution that accounts for the effects of the confining boundaries that usually exist in real systems. We use such a setup to provide the benchmarking of the different averaging techniques for the calculations of properties at the cell faces and center, particularly in the cells involving the interface. Full article
(This article belongs to the Special Issue Flow and Transport in Membranes: Modeling and Experimental Verification)
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18 pages, 4186 KiB  
Article
Computational Fluid Dynamics (CFD) Modeling and Simulation of Flow Regulatory Mechanism in Artificial Kidney Using Finite Element Method
by Tuba Yaqoob, Muhammad Ahsan, Arshad Hussain and Iftikhar Ahmad
Membranes 2020, 10(7), 139; https://doi.org/10.3390/membranes10070139 - 3 Jul 2020
Cited by 6 | Viewed by 5279
Abstract
There is an enormous need in the health welfare sector to manufacture inexpensive dialyzer membranes with minimum dialysis duration. In order to optimize the dialysis cost and time, an in-depth analysis of the effect of dialyzer design and process parameters on toxins (ranging [...] Read more.
There is an enormous need in the health welfare sector to manufacture inexpensive dialyzer membranes with minimum dialysis duration. In order to optimize the dialysis cost and time, an in-depth analysis of the effect of dialyzer design and process parameters on toxins (ranging from tiny to large size molecules) clearance rate is required. Mathematical analysis and enhanced computational power of computers can translate the transport phenomena occurring inside the dialyzer while minimizing the development cost. In this paper, the steady-state mass transport in blood and dialysate compartment and across the membrane is investigated with convection-diffusion equations and tortuous pore diffusion model (TPDM), respectively. The two-dimensional, axisymmetric CFD model was simulated by using a solver based on the finite element method (COMSOL Multiphysics 5.4). The effect of design and process parameters is analyzed by solving model equations for varying values of design and process parameters. It is found that by introducing tortuosity in the pore diffusion model, the clearance rate of small size molecules increases, but the clearance rate of large size molecules is reduced. When the fiber aspect ratio (db/L) varies from 900 to 2300, the clearance rate increases 37.71% of its initial value. The results also show that when the pore diameter increases from 10 nm to 20 nm, the clearance rate of urea and glucose also increases by 2.09% and 7.93%, respectively, with tolerated transport of albumin molecules. Full article
(This article belongs to the Special Issue Flow and Transport in Membranes: Modeling and Experimental Verification)
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