Efficient Removal Of Water Research Articles

Proposal automatic water purging system for machinery in high humidity environments controlled by an ECU

This paper presents an advanced automatic water discharge system tailored for diesel-powered machinery, particularly for vehicles operating in diverse climates, including humid coastal regions. The system is designed to protect fuel circuits in tanks and diesel engines of boats, offering either automatic or semi-automatic protection against oxidation and corrosion. This enhancement extends the lifespan of diesel components and pipelines while simultaneously reducing maintenance costs and intervention times. Additionally, the system improves fuel purity, resulting in increased engine power and efficiency. The proposed solution was experimentally validated using an Arduino board coupled with a water-sensitive detector in diesel fuel, suitable for installation in diesel filters or tanks. Experimental findings demonstrated a remarkably swift separation time of 150 microseconds for diesel and water at a pressure of 1 bar, achieving an impressive efficiency of 99.84%. The system's rapid and effective separation capability highlights its practical value, particularly in scenarios where efficient water removal is critical to sustaining engine performance and longevity.

Dual functionality of cathode microporous layers: Reducing hydrogen permeation and enhancing performance in proton exchange membrane water electrolyzers

Hydrogen permeation and cell performance are critical factors for the safe and efficient operation of proton exchange membrane (PEM) water electrolysis. In this study, the effects of a cathode microporous layer (MPL) on water transport, hydrogen permeation, and cell performance in a proton exchange membrane water electrolyzer (PEMWE) were investigated. Results reveal that adding an MPL between the catalyst layer (CL) and the porous transport layer (PTL) at the cathode reduces interfacial contact resistance by approximately 60 % under 400 N cm−2, leading to superior performance. The wettability of the MPL plays a crucial role in water transport and hydrogen permeation in PEMWEs. The hydrophobic MPL-P-CB4, which uses polytetrafluoroethylene (PTFE) as a binder with a carbon black (CB) loading of 4 mgCB cm−2, enhances the crossover of water and hydrogen from the cathode to the anode through back diffusion, exceeding the technical safety criterion of 2 vol% H2 in the anode product gas (50 % lower explosion limit) at 2.0 A cm−2. However, the hydrophilic MPL with Nafion ionomers as binders (MPL-N-CB4) facilitates efficient removal of water and hydrogen from the cathode CL to the cathode flow field via capillary pressure, resulting in only 0.2 vol% H2 in O2 at 2.0 A cm−2. Consequently, a hydrophilic MPL is optimal for achieving superior performance and low-hydrogen-crossover in a PEMWE cathode. This study provides valuable insights for designing the PTL/CL interface in next-generation PEMWE cathodes.

The effect of pin-type flow field plate design on the current distribution in a H2-fed polymer electrolyte fuel cell

The flow field plate (FFP) design is a key factor for enhancing the electrochemical performance of Polymer Electrolyte Fuel Cells (PEFCs) through optimal reactants’ distribution, low-pressure drops, and efficient water removal. The effect of geometrical features of the pin-type FFP design on the electrochemical performance of a 48 cm2 H2-fed Fuel Cell (FC) was assessed through polarization curves recording and current and temperature distribution maps along the electrode active area. The study was performed by changing excess air stoichiometry and cathode relative humidity (RH). Low-pressure drops were measured using pin-type FFPs; regardless of geometrical features, they were one order of magnitude lower than those of a single-channel serpentine FFP. Channel width and number of pins greatly influenced the current distribution along the active area and, consequently, the electrochemical performance of FCs. In particular, the best electrochemical performance was reached at air stoichiometry 4 and cathode RH = 100 % by using FFP with the highest coverage factor (65 %) and the lowest channel width (1 mm). Current distribution maps demonstrated that this FFP geometry led to an almost homogeneous current distribution and efficient water removal also at high current density values. On the contrary, low coverage factor (45 %) and high channel width led to worse electrochemical performances due to an uneven reactants distribution and an inefficient water removal, causing cell flooding.

Base-Driven Ring-Opening Reactions of Vinylene Carbonate

Vinylene carbonate (VC) is the most commonly applied performance-enhancing electrolyte additives in Li-ion batteries to date. Despite numerous studies, there is a lack of consensus regarding the various reaction pathways of VC and their implications. VC has primarily been observed to either polymerize forming poly(vinylene carbonate) (poly(VC)) or decompose releasing major amounts of CO2, two seemingly contradictory processes. Herein, we present evidence of additional reaction pathways of VC highlighting its role as a H2O scavenging agent. In contrast to the typical electrolyte solvent ethylene carbonate, VC reacts much more rapidly with water impurities, especially when in contact with hydroxides, forming products less likely to influence cell performance. Efficient removal of water and hydroxides is essential to preserve the stability of Li-ion electrolyte solvent and salt, hence guaranteeing a long lifetime of the battery. Model studies pinpointing reaction pathways of electrolytes and additives, as presented herein, are critical not only to improve modern Li-ion cells but also to establish design principles for future battery chemistries.

Effectiveness of biological drying for citric acid dewatered sludge: Evaluating the impact of energy-efficient ventilation strategies

The effectiveness of dehydration and utilization processes for citric acid dewatered sludge is hampered by its high concentrations of polysaccharides, proteins, and water-binding properties of microbial extracellular polymers (EPS). This research explores the efficacy and mechanisms involved in extracting water from this type of sludge using biological drying technology, with varying rates of ventilation. Especially pertinent was the use of low ventilation rates as control variables. Our results suggest that a scheduled intermittent ventilation at lower rates allows for the most efficient removal of water, achieving a rate of 41.71 % within eight days, according to the zero-order kinetic model. Remarkably, the peak temperature registered was 60 °C, reaching this threshold in just 0.1 days and maintaining high temperatures for approximately 5.9 days. Component analysis of organic matter illustrated a preferential degradation process for lipids under these ventilation conditions which is pivotal for releasing and transforming bound water for efficient extraction, as well as facilitating the breakdown of easily hydrolysable materials. Further, polysaccharide/protein (EPS) decomposition contributed to water removal, though less significantly. The periodic ventilation strategy allowed for the maximum cumulative temperature to be sustained, demonstrating superior efficiency in harnessing bio-generated heat (82.77 % for water evaporation), resulting in dry sludge suitable for self-sustained combustion at relatively low cost ($26.61/t). Highlighted by this study is the considerable potential of energy-efficient ventilation methods in the biological drying treatment of citric acid fermented sludge and similar industrial waste materials.

Methanation of syngas from biomass gasification: Small-scale plant design in Aspen Plus

The objective of this study is to investigate the upgrading of low-quality nitrogen-diluted syngas derived from biomass air gasification processes into a methane-rich gas stream. Both the thermodynamic and the kinetic aspects are addressed in the paper. Using the Aspen Plus software, a thermodynamic analysis was conducted; then, different plant designs are simulated and compared, including reactor sizing and performance. The results demonstrate that the upgrading of diluted syngas poses challenges which limit its application to small-scale decentralized systems. It was found that a system comprising of four adiabatic fixed-bed reactors, inter-cooling, and efficient water removal achieves a favorable balance between performance and cost. Operating the system at a pressure of 5 bar is deemed adequate as it reduces the required catalyst mass and prevents solid carbon deposition. Notably, this configuration achieved good results, including a 99.4 % CO conversion, 89.3 % CO2 conversion, and 95.6 % CH4 yield. The final methane molar content reached 26.4 %, with a calorific value of 8.62 MJ/Nm3(STP).

1D Spatially Resolved Model of Alloyed Catalyst Degradation in LT-PEMFC

Low-temperature fuel cells with proton exchange membrane (LT-PEMFC) are among the most promising energy devices for future decarbonizaion of heavy-duty long-distance transport. Fuel cells use hydrogen as the energy source and air as oxidizer to produce electricity in catalyzed electrochemical process, with only side-products being heat and water. Despite some clear advantages over other energy sources, i.e. batteries, their adoption is still somewhat limited by some prominent factors such as high price and limited durability. Both of these factors are closely related to the use of specific catalyst materials needed to ensure high efficiency and power density of hydrogen fuel cells. Due to its high catalytic activity, Pt is traditionally used as a catalyst material, dispersed in form of nanoparticles on a highly porous carbon matrix ensuring good accessibility of hydrogen and air to the catalyst surface and efficient removal of water.Due to harsh local conditions in the catalyst layer, i.e. high temperatures of up to 80° C, high humidity and high electric potentials, catalyst nanoparticles are exposed to various degradation processes. Electrochemical corrosion of carbon support can result in detachment of particles and their consequent agglomeration, which results in a decrease of specific area suitable for electrochemical reactions. Despite high redox potential of Pt (1.115 V vs. SHE), high electric potential in fuel cell cathode can also lead to electrochemical dissolution of catalyst particles, which is additionally accelerated by their small size. Dissolved catalyst can either redeposit to larger particles, resulting in net growth of catalyst particles (so-called Ostwald ripening), or diffuse in proton exchange membrane, where it is reduced by crossover hydrogen. Both processes result in a loss of electrochemically active surface area in the catalyst layer.To reduce the amount of Pt used and thus lower the price, new types of catalyst materials are being developed, using alloys of Pt with other metals, such as Co, Cu or Ni, which also increases the specific electrochemical activity of the material. [1] Since alloying metals have lower redox potential compared to Pt, alloyed catalyst are more susceptible to dissolution, which represents a significant challenge in their wider adoption. Degradation is somewhat mitigated by preconditioning of catalyst nanoparticles during which Pt shell is formed around alloy particle core, resulting in higher stability of core-shell catalysts. Despite clear advantages, the use of alloyed catalyst might introduce some new risks in terms of fuel cell durability. Dissolution of alloying metal introduces ions of transition metals into the membrane, where they could serve as a catalyst in chemical reactions leading to the chemical degradation of the membrane [2]. Metal ions can also block the active sites in proton exchange membrane and thus reduce its proton conductivity, while diffusion from cathode to anode catalyst layer and deposition on catalyst surface can present a risk of anode catalyst surface passivization [3].To improve the understanding of aforementioned processes, we propose a 1-dimensional spatially and temporally resolved degradation model of alloyed catalyst degradation in the membrane-electrode assembly (MEA). The model describes the changes of cathode core-shell catalyst structure as a redistribution of particle core sizes and shell thicknesses due to electrochemical surface oxidation, dissolution and redeposition. To provide realistic internal states of the fuel cell during operation, the degradation model is coupled with advanced spatially and temporally resolved model of the fuel cell operation [4]. Dissolution model represents a source of Pt and alloying ions in the catalyst layer, which is coupled to 1D model of ion diffusion in the catalyst layer and the membrane, taking into account the specifics of transport in different MEA components. The transport model is further coupled with potential ion sinks, such as reduction in the presence of hydrogen, interaction with the proton exchange membrane and redeposition on the anode.Preliminary results indicate that Pt ions diffusion results in spatial inhomogeneities of catalyst layer degradation. The location and mechanism of metal ion deposition depends on the redox potential of metal and can occur in either membrane or anode catalyst layer. The model shows great promise in developing a better understanding of degradation processes of alloyed catalyst materials and could in future guide a development of better operation strategies for fuel cell use, mitigating their degradation and improving their lifetime.[1] E. Antolini et al., J. Power Sources. 160 (2006) 957–968.[2] M. Strlič et al., Acta Chim. Slov. 50 (2003) 619–632.[3] A. Han et al., Int. J. Hydrogen Energy. 45 (2020) 25276–25285.[4] A. Kregar et al., Appl. Energy. 263 (2020) 114547

Transient characteristics of in-plane water transport in gas diffusion layers of PEM fuel cells

During the operation of proton exchange membrane (PEM) fuel cells, water and heat are produced as two byproducts. A reliable and continuous operation of a PEM fuel cell requires an efficient water removal from the porous structure of the electrodes. In PEM fuel cells, gas diffusion layers (GDL) are used to effectively remove the produced water from the electrodes and also to supply reactant gases across them. The focus of this study is to characterize liquid water percolation within the plane of the GDL by utilizing a nondimensional energy ratio-time scale model (Ce-t∗). The transport phenomena are investigated for various GDL compressions, GDL samples with the microporous layer (MPL), and a degraded GDL sample. The transition between flow regimes is characterized based on the variation of slopes in Ce-t∗ curves. The flow regimes were observed to change from fingering and channeling in the capillary fingering regime to macro-transport along with uniform percolation in the stable displacement regime. It was observed that GDL compression can expedite flow regime transition and can cause faster energy dissipation during steady state periods. When MPLs were added to the GDL, the wetted areas were observed to occur at more dispersed locations. Finally, the experiment conducted with a degraded GDL without an MPL demonstrated higher slopes in the Ce-t∗ curve, indicating more frequent liquid water flooding. This could ultimately result in reduced cell performance.

Improving water removal efficiency in a PEM fuel cell: Microstructured surfaces for controlling instability-driven pinching

Proton Exchange Membrane Fuel Cell (PEMFC) is a clean, sustainable energy generation device, and its large-scale usage is becoming popular due to green and secure energy demand worldwide. The performance, efficiency, and lifespan of PEMFC largely depend on the water removal and management within the cell. Under the influence of the cross-air flow, the generated water filaments deform, and as the filament radius lowers, the curvature and capillary pressure increase, ejecting fluid out of the neck at increasing velocities. The moment the filament radius vanishes, the governing equations reach the point of singularity, and the filament breaks. We propose an optimum micro-patterned surface design for efficient water removal from PEMFC. We perform a numerical study of water generation on the surface followed by breakup under shear flow within confinement. We further theoretically identify the breakup behavior with characterization, recognizing the influence of the microstructures toward an efficient design. The hydrophobic microstructures are observed to decrease the dominance of viscous force over inertia and capillary force. This leads to a greater propensity of end-pinching or truncation of the generated droplet at the neck, which reduces the production of undesired satellite droplets that would have otherwise caused flooding of the chamber. In this work, we show that a proper combination of substrate structure and jet velocity-induced shear can mitigate the generation of satellite droplets and reduce the breakup time, significantly increasing the water removal efficiency of the PEMFC.

Facile tuning of hydrogel properties for efficient water removal from biodiesel: An assessment of alkaline hydrolysis and drying techniques

Polymeric hydrogels are a promising new technology for dehydrating fuels. This study critically analyzes the effects of hydrolysis post-treatment and drying methods (oven-drying and freeze-drying) on polyacrylamide hydrogels for removing diluted water from biodiesel. The materials were characterized using FTIR, TGA, SEM, DVS, compressive strength, and swelling degree analyses. The water diffusion profiles during swelling were observed using an innovative method described in this study. Hydrolysis improved the hydrophilicity of the hydrogel, increasing the swelling degree from 33–37 g.g−1 to 987–1,095 g.g−1, and doubling the water absorption from biodiesel. Freeze-drying benefited the kinetics of water uptake. Using hydrolyzed polyacrylamide hydrogel, the water content in biodiesel decreased from 1497 ppm to 978 ppm in just 30 min. Within 72 h, 49% of the water was removed from the biofuel. This demonstrates the efficiency of hydrogel systems, which could become a competitive alternative to traditional fuel desiccants, removing even traces of moisture.

Stable and Continuous Production of Amines via Reductive Amination in a Green Switchable Solvent System with Efficient Water Removal

Stable and Continuous Production of Amines via Reductive Amination in a Green Switchable Solvent System with Efficient Water Removal

Design of amphoteric micro/nanofiber-coupling fabric for ultrafast, precise, and robust removal of water droplets from oils

The main problem affecting oil applications is water contamination, which causes reduced oil film strength, additive failure, oil foaming, lubricating oil mildew, etc., with serious impacts on the industry and the environment. However, the use of existing filtration-based or adsorption-based oil–water separation technologies to simultaneously achieve rapid, precise, and sustainable removal of water droplets from oil is extremely challenging. Herein, we designed and constructed a robust amphoteric micro/nanofiber coupling fabric (AMCF) that combines the advantages of traditional filter type and adsorption type oil–water separation materials to achieve rapid, accurate, and efficient removal of water mixed in oil. Compared to traditional oil–water separation materials, the AMCF enables the ultrafast and precise removal of small water droplets (3 mL) in various oils within 1–3 s. Importantly, the outer layer, separation flux up to 33,792 L·h−1·m−2, can resist extremely harsh mechanical and chemical damage, while the inner layer has excellent water absorption ability, ensuing the AMCF with robust water removal ability after multiple cycles of drying state–water absorption saturation state. This work provides insights into the design of systems for removing water from oil in complex environments, with a promising potential for real-world applications.

Composite Salting-out Agent for the Salting-out of Ethanol, Acetone and n-butanol in the Crude Alcohol

This paper introduces the salting-out technology of ethanol, acetone and n-butanol in the crude alcohol after the bio-butanol fermentation liquid is processed by the mash tower. Aiming at the problems of low total solvent concentration, difficult recovery and high energy consumption for the bio-butanol fermentation broth separation, this paper studied the effects of unsaturated composite salts, salting-out temperature, and the volume ratio of salting-out agent to crude alcohol on the water removal of bio-butanol system. According to the index of water content in the organic phase, the most beneficial salting-out agent for water removal was selected from various composite salts. A salting-out extractant composed of water and composite salts was developed. The results showed that the extraction effect of unsaturated salt was not good for n-butanol-acetone-ethanol-water system. The n-butanol-acetone-ethanol-water system is extracted with a composite salt and water extractant, which can increase the mass fraction of n-butanol, acetone and ethanol, and achieve the purpose of separating and concentrating n-butanol, acetone and ethanol. After the primary countercurrent extraction, the mass fraction of n-butanol in the organic phase increased from 26% to over 64%, the mass fraction of acetone increased from 10% to over 21%, and the mass fraction of ethanol increased from 4% to over 9%. The composite salting-out agent can achieve the purpose of efficient water removal.

Facile Synthesis of Quinolinecarboxylic Acid-Linked Covalent Organic Framework via One-Pot Reaction for Highly Efficient Removal of Water-Soluble Pollutants.

To efficiently eliminate highly polar organic pollutants from water has always been a difficult issue, especially in the case of ultralow concentrations. Herein, we present the facile synthesis of quinolinecarboxylic acid-linked COF (QCA-COF) via the Doebner multicomponent reaction, possessing multifunction, high specific surface area, robust physicochemical stability, and excellent crystallinity. The marked feature lies in the quinolinyl and carboxyl functions incorporated simultaneously to QCA-COF in one step. The major cis-orientation of carboxyl arms in QCA-COF was speculated by powder X-ray diffraction and total energy analysis. QCA-COF demonstrates excellent adsorption capacity for water-soluble organic pollutants such as rhodamine B (255.7 mg/g), methylene blue (306.1 mg/g), gentamycin (338.1 mg/g), and 2,4-dichlorophenoxyacetic acid (294.1 mg/g) in water. The kinetic adsorptions fit the pseudo-second order model and their adsorption isotherms are Langmuir model. Remarkably, QCA-COF can capture the above four water-soluble organic pollutants from real water samples at ppb level with higher than 95% removal efficiencies and excellent recycling performance.

How to stabilize standard perovskite solar cells to withstand operating conditions under an ambient environment for more than 1000 hours using simple and universal encapsulation

We introduce a simple and universal scalable encapsulation strategy for perovskite solar cells based on thermal vacuum evaporation of MgF2 or MoO3-x capping layer followed by sealing the device with glass and UV-curable polymer. The proposed encapsulation method is beneficial to most of the other known encapsulation approaches being fully harmless to perovskite and transporting layers and processible at room temperature. Vacuum deposition of the capping layer promotes efficient removal of water, oxygen and organic solvent residuals from the device prior to sealing and could be easily performed using standard equipment for metal electrode deposition. The proposed strategy is transferrable to any lab-scale perovskite solar cell prototypes regardless of their geometry and architecture and results in excellent stability of the devices in ambient air and long operating conditions. Upon the 1000 hours stability test at ambient air (30%-60% RH), the cells preserved 92.9% of their initial efficiency on average under 1 Sun illumination at constant maximum power point tracking (MPPT, ISOS-L-1) and over 96% under storage in the dark (ISOS-D-1), thus evidencing for the high effectiveness of the proposed encapsulation approach.

Co-treatment of municipal solid waste incineration fly ash (MSWI FA) and municipal sludge: A innovative method to improve sludge dewatering with fly ash dechlorination

The complexity of municipal sludge dewatering is a bottleneck problem limiting resource utilization. In this paper, adding municipal solid waste incineration fly ash (MSWI FA) to municipal sludge for enhanced dewatering was applied, while the chlorine salt in MSWI FA was simultaneously removed using water in municipal sludge. The effects of different dosages and chemical components of MSWI FA on municipal sludge dewatering, and the removal effect of municipal sludge washing on Cl element were investigated. The results showed that the municipal sludge's specific resistance to filtration after co-treatment was significantly reduced, and more hydrophobic channels were formed in the vacuum suction filtration of the treated municipal sludge, conducive to efficient water removal. The moisture content of municipal sludge was reduced from 96.0% to 48.3%, and the moisture reduction rate increased from 17.7% to 32.1%. The chemical composition of MSWI FA could effectively promote the dewatering of municipal sludge, among which CaO was the best, followed by CaCl2 and NaCl, and KCl was the worst. Simultaneously, the municipal sludge showed a good effect on removing Cl from MSWI FA. The minimum Cl content in the mixture after Co-treatment is 1.5%. These results could provide a new way to dispose of MSWI FA and municipal sludge.

Impact of surface cooling on the water harvesting efficiency of nanostructured window glass.

Humans face a severe shortage of fresh water due to economic growth, climate change, overpopulation, and overutilization. Atmospheric water harvesting (AWH) is a promising solution where clean water is collected from the air through various approaches, including dropwise condensation. However, designing surfaces that balance rapid condensation with efficient water removal is challenging. To address this issue, inspired by the efficient water collection mechanisms in the skin of cold-blooded tree frogs, we propose an eco-friendly approach to collect fresh water from cooled window glass. We fabricated various planar and TiO2 nanostructured surfaces including surfaces mimicking a lotus leaf and a hybrid surface mimicking a desert beetle and a cactus, with different wettability levels such as superhydrophilic, hydrophilic, hydrophobic, superhydrophobic, and biphilic. Sub-cooling of glass substrates between 5 and 15 °C using a Peltier device significantly enhanced the condensation process for all surfaces, with modest dependency on surface properties. This cooling temperature regime could be achieved by geothermal cooling methods that consume little energy. To improve visibility for window applications, we developed hydrophobic polymer nanofilm-modified glass substrates using a simple spin-coating technique, and achieved comparable water harvesting efficiency to that of nanostructured substrates. Our study provides insight into the optimal surface structures and cooling temperature for window glass AWH systems that could be used with an underground cooling system.

Fabrication and Performance Evaluation of Tubular Catalyst Layer for Proton Exchange Membrane Fuel Cell

Over the past several decades, planar proton exchange membrane fuel cells (PEMFCs) received considerable attention due to their simple structure, manufacturing, and easy integration. However, current PEMFC electrode designs are disadvantaged by high cost, insufficient mass transport, nonuniform reactant, current and temperature distribution, and limited water removal. The development of a novel tubular fuel cell design could address these challenges. Tubular-shaped PEMFC offers several advantages over planar one, including lower pressure drop, efficient water removal, reduced mass transport losses, and cost reduction owing to removing one of gas diffusion layer/bipolar plate (GDL/BPP) side.This work developed a carbon nanofiber (CNF)/Pt-based cathode for a tubular fuel cell. The tubular CNF support for Pt catalyst was fabricated employing the electrospinning method. Polyacrylonitrile (PAN) was used as the precursor. The electroless deposition of Pt using the chloroplatinic acid solutions was applied to produce well-dispersed low Pt loading nanowires. The tubular CNF/Pt electrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ex-situ cyclic voltammetry to determine the CF and Pt morphology and feasibility of the prepared layer in PEMFC application. SEM images indicated that increasing the Pt precursor concentration in the plating bath leads to higher Pt loading and larger Pt clusters on the CNF surface. The calculated electrochemical active surface area (ECSA) trend imparts that high Pt loading is less favorable as thick Pt layers lead to low Pt utilization and increased material costs. ECSA results agreed with SEM images, suggesting that the medium Pt concentration (1.5 g L-1 Pt precursor) developed a homogenous Pt distribution and comparable Pt surface area of 24 m2 gPt -1 for the Pt loading of 0.046 mg cm-2, proving the feasibility of the proposed process.

Efficient water removal from water-in-oil emulsions by high electric field demulsification

ABSTRACT Following hydrothermal liquefaction (HTL), microalgae bio-crude products contain approximately 5–20% water. High electric field (HEF) demulsification can separate water from settled oil based on electrostatic charge. In this study, we investigated the effect of HEF demulsification on water-in-oil (W/O) emulsions as a model bio-crude emulsion using a batch-type coalescer. Three W/O emulsions of soybean oil, medium-chain triglyceride (MCT) oil, and castor oil (10 wt% water content) were prepared and exposed to an alternating current electric field at different voltages (1000–4000 V) and frequencies (50–2000 Hz) for 1 h. Water content in castor oil samples declined to 9.6–8.6 wt% from the initial 10 wt% as the applied voltage increased at 50 Hz after 1 day storage. A noticeable difference in the remaining water in the oil occurred between samples exposed to 50 Hz and 500 Hz at 4000 V. The water content declined to 1.8 and 1.4 wt% (MCT oil); 4.3 and 1.8 wt% (soybean oil); and 8.4 and 8.1 wt% (castor oil) at 50 Hz and 500 Hz, respectively, at 4000 V. Moreover, HEF demulsification consumed negligible energy compared to centrifugation (1.37 × 103 J/kg versus 2.71 × 1010 J/kg).

Lattice Boltzmann simulation of liquid water transport in gas diffusion layers of proton exchange membrane fuel cells: Parametric studies on capillary hysteresis

Water management is crucial for reliable operation of Polymer Electrolyte Membrane Fuel Cells (PEMFC). Here, the gas diffusion layer (GDL) plays an essential role as it has to ensure efficient water removal from and oxygen transport to the catalyst layer.In this study water transport through porous carbon felt GDLs was simulated using a 3D Color-Gradient Lattice Boltzmann model. Simulations were carried out on microstructures of plain and impregnated fiber substrates of a Freudenberg H14. The GDL microstructures were reconstructed from high-resolution X-ray micro-computed tomography (μ-CT). For the distinction of carbon fibers and polytetrafluoroethylene (PTFE) in the binarized microstructures an in-house algorithm was developed. The additive was specified heterogeneously in the GDL through-plane direction employing a PTFE loading profile as derived based on μ-CT image data. In the in-plane direction the additive was furthermore defined in a realistic fashion near carbon fiber intersections. Prior to parametric studies on capillary behavior a sophisticated modeling approach for semipermeable membranes had to be developed to account for experimental boundary conditions. Capillary hysteresis was then investigated by simulation of intrusion and drainage curves and subsequent comparison to testbench data.