Flow Field Plate Research Articles

Pre-bent Flow-Field Plates for Enhanced Performance in Flexible Polymer Electrolyte Membrane Fuel Cells in Curved Shape

This article reports on a flexible polymer electrolyte membrane fuel cell (PEMFC) with a pre-bent flow field. The performances in the flat and bent positions were lower and higher, respectively than that of the traditional flexible fuel cells. The low performance in the flat position was attributed to the void space induced incomplete contact at the interface of the membrane electrode assembly (MEA) and flow-field plates, which resulted in poor performance due to the high ohmic resistance (5.85 Ω cm2) and faradaic resistance (4.17 Ω cm2). However, when bending stress was applied to the MEA, a decreased ohmic resistance (0.954 Ω cm2), faradaic resistance (0.737 Ω cm2), and an enhanced power density (88.7 mW/cm2) were observed because of the improved interfacial contact property between the MEA and the flow-field plates from the increased compressive stress. These experimental results were further analyzed and visualized with aid of the finite element analysis. Despite the relatively low performance in the flat shape, the proposed pre-bent design of the flexible PEMFC possesses promising applicability especially in flexible electronics where the curved shapes are highly required.

Multi-angle study of the effects of different wave flow field plates on fuel cell performance

The flow field plate is an important component of the fuel cell, and makes the flow state of the reactant gas produce obvious changes. In this paper, the method of computational fluid dynamics was used to study the influence of the waveform channel on the internal parameters of the fuel cell. Through analysis, the optimal cathode flow field waveform at different temperatures was determined. It was found that the waveform flow field plate is very limited in improving the average current density. The existence of the waveform would obviously change the distribution of liquid water. This paper has contributed to the full commercialization of fuel cells.

Numerical analysis of wave‐shaped flow field plate for proton‐exchange membrane fuel cell

The change of the geometry of the flow field plate will affect the distribution of reaction gas and further change the reaction rate inside the cell. This article uses computational fluid dynamics as a research method to observe the improvement of fuel cell performance of different channel geometries. In the single-channel simulation, channel of different shapes has very limited influence on current density, but it will change the water saturation, especially near the outlet of the channel. In this research, the performance of a variable waveform flow field plate is relatively better. This will be conducive to the promotion and application of proton-exchange membrane fuel cells in real life.

Study of new flow field geometries to enhance water redistribution and pressure head losses reduction within PEM fuel cell

Efficiency of fuel cell is dependent on reactant distribution, products evacuation, pressure losses and many of these factors is dependent on the design of flow field plate. With an effective design, reactant distribution, pressure drop, and water and heat management can be further improved. In this work, two new designs, as multi-serpentine set-up with additional slots and hybrid geometry, on stainless steel bipolar plates, are presented. Electrical performance, and pressure head losses are analyzed by electrochemical methods such as polarization curve and use of electrochemical noise as a diagnostic tool to further understand the impact of water management on performance. On the one hand, multi-serpentine design shows the best electrical performance with an increase of 0.2 V (66%) at 0.9 A/cm2 in comparison of traditional serpentine design. On the other hand, hybrid design reveals the lowest pressure head losses, with a decrease of 2 mbar (about 50%) in comparison of traditional serpentine design, and a higher stability with time that can be useful to downsize compressor and provide lower impact on fuel cell stack durability.

Investigations on a platinum catalyzed membrane for electrolysis step of copper‐chlorine thermochemical cycle for hydrogen production

SummaryConsidering the low temperature demand (~550°C maximum) and high efficiency (~43%), Cu–Cl thermochemical water splitting cycle has immense potential as a futuristic scalable hydrogen generation process. CuCl/HCl electrolysis is the crucial hydrogen generation step in the Cu–Cl thermochemical cycle. The efficiency of this electrolysis process is highly dependent on the performance of the membrane electrode assembly (MEA) employed. To explore the suitability of the platinized membrane for this step, in this study, we have investigated a Pt/Nafion‐117 MEA prepared by in‐situ impregnation‐reduction method for CuCl/HCl electrolysis. A single‐cell PEM‐type electrolyser (4 cm2 active area) consisting of serpentine channels (2 cm × 2 cm) grooved in graphite flow field plates was designed and fabricated to carry out the CuCl/HCl electrolysis. Platinum electrocatalyst was deposited on Nafion‐117 membrane on the cathodic side by reduction of hexachloroplatinic acid (H2PtCl6) with sodium borohydride (NaBH4) by the impregnation‐reduction method which served as the MEA. Monodispersed nanocrystalline Pt particles formed a ~30 μm thick electrocatalyst layer on the membrane. Pt/Nafion‐117 MEA was found to be effective for CuCl /HCl electrolysis. In a PEM‐type electrolyser with Ar‐purged 0.2 M CuCl in ~2 M HCl solution as anolyte flowing at ~ 8.8 mLmin−1, a current density of ~100 mA cm−2 was achieved at a cell voltage of 1 V. However, undesired Cu‐crossover could be noticed from anode to cathode side during operation.

Finite Element Model Based Determination of Local Membrane Conductivity of Polymer Electrolyte Fuel Cells

Polymer Electrolyte Fuel Cells (PEFCs) are an essential technology for future fast refill, long range and clean mobility. However, for better market penetration, their efficiency still needs to be improved. An important aspect, leading to different kinds of losses is the water management. Indeed, there exists a humidity gradient between the gas inlet and gas outlet in PEFCs with active areas of some hundred cm². This can lead to uneven membrane conductivity over the cell area which results in current density inhomogeneities, resulting in lower cell efficiency and shorter lifetime. Therefore, the measurement of localized membrane conductivity in technical cells is of great importance. Different to the typical invasive membrane conductivity measurement techniques, such as segmented flow field plates or shunt resistor boards, we propose a non-invasive method [1] which is able to provide localized information about the ionic conductivity in the membrane using electrical impedance tomography (EIT). EIT is based on the relationship that exists between one object’s conductivity distribution and the surface potential that one could measure when an alternating current is applied to the object. The objects surface potential is measured during the injection of an alternating current between two electrodes at the remaining electrodes (see Figure 1). Once enough injection-measurement pairs have been acquired, the objects inner conductivity can be reconstructed.This presentation will discuss the results of a numerical feasibility study of the application of EIT for the determination of the membrane conductivity in PEFCs. A finite element model (FEM) based representation of a simplified fuel cell geometry is used to solve the surface potential distribution as function of the membrane conductivity distribution and current injection. Using a minimization approach the membrane conductivity distribution is adjusted such that the mismatch between the surface potential of the FEM solution and synthetic measurement data is reduced. In order to simplify the problem and reduce the degree of freedoms in the minimization formulation, so far, the conductivity distribution in the membrane is estimated by 1D interpolations from cell inlet to cell outlet (see Figure 2). Finally, the working principle of the method is experimentally demonstrated using fuel cell relevant materials.[1] 2019P04382EP patent application Figure 1

Comparison of Planar and Tubular Flow Field Plates for Proton Exchange Membrane Fuel Cells (PEMFCs) through Simulation

The proton exchange membrane fuel cell (PEMFC) is an excellent clean energy alternative to current non-renewable energy sources. Bipolar plates (BPPs) are a key component of these PEMFCs and are directly responsible for their performance. Much research has been invested in channel design, materials characterization, and interfacial phenomenon of BPPs but not much attention has been paid to the architecture of the plate itself. Traditional BPPs are created in a planar form, but recent research efforts have revealed a novel tubular design that performs equally as well if not better than conventional plates. This study will experiment with three different channel designs for both planar and tubular plate configurations. The finite element ANSYS software will be used to determine and visualize velocity and pressure distributions of fluid flow through the BPP channels. Results from this study will validate whether the tubular configuration is superior to the planar form as well as which channel design is most appropriate for either configuration.

Bio-inspired design of an auxiliary fishbone-shaped cathode flow field pattern for polymer electrolyte membrane fuel cells

A bio-inspired auxiliary fishbone-shaped flow field (AFFF) pattern is proposed and designed at the cathode flow field plate (FFP) of polymer electrolyte membrane (PEM) fuel cells, in order to enhance under-rib mass transport and water removal from gas diffusion layer (GDL). The bio-inspired AFFF pattern is numerically investigated by a three-dimensional multiphase fuel cell model. It is shown that the AFFF pattern significantly improves under-rib mass transport and water removal ability, hence fuel efficiency is improved. In comparison with the conventional parallel flow field (CPFF) pattern, the new pattern exhibits higher uniformity of reactants and saturation distributions, and thereby improving the operation stability of fuel cells. Furthermore, sub-branch channels of various numbers and widths in the AFFF pattern are evaluated with consideration of electrical contact resistance (ECR) between the FFP and GDL. Under-rib mass transport and water removal is improved when increasing the number and width of sub-branch channels. However, the ECR somehow increases as well. Therefore, counterbalance between under-rib mass transfer and ECR should be considered. Finally, the AFFF pattern with an optimized combination between number and width of sub-branch channels is achieved to improve the maximum power density of fuel cells.

Numerical study on the performance of fuel cell with wavy flow field plate

Fuel cell is one of the most promising batteries at present. However, in order to successfully use fuel cell in vehicle, many improvements are still needed. Among them, the flow field plate of fuel cell has an important impact on the performance of fuel cell. In this paper, the influence of the wave channel on the internal pressure, current density, and water content of the fuel cell was studied. After analysis, the influence of the height of flow passage, the number of wave peaks, and wave amplitude on the cathode of the fuel cell was determined. The performance of the fuel cell was successfully improved, and the possible improvement direction of the cathode flow field plate of the fuel cell was further explored.

Comparison of Planar and Tubular Flow Field Plates for Proton Exchange Membrane Fuel Cells (PEMFCs) through Simulation

Proton exchange membrane fuel cells are excellent clean energy alternatives to current non-renewable energy sources. Bipolar plates are a key component of these fuel cells and directly responsible for their performance. Traditional bipolar plates are created in a planar form, but recent research has revealed a novel tubular design that performs similarly to conventional plates. This study compares traditional planar designs with tubular ones. The finite element ANSYS software was used to determine and visualize velocity and pressure distributions of fluid flow through the bipolar plate channels.

In the Race for Future Energy Provision

AbstractNo abstract.

Numerical investigation of novel bio-inspired flow field design scheme for PEM fuel cell

The uniformity of reaction gas distribution and water drainage performance may be influenced by the flow field structure and the total distance between the inlet and outlet of a proton exchange membrane (PEM) fuel cell. Therefore, the design of flow field plates may dominate the performance of fuel cells to some extent. A new kind of flow field plate structure is presented here based upon the principle of bio-inspiration and Murray's law in view of a PEM fuel cell as the object; moreover, numerical simulation is carried out to determine performance. In addition, contour plot comparisons between the bio-inspired and parallel flow fields of the PEM fuel cell indicate that the molar concentration distributions (O2, H2, and H2O) are more even for the bio-inspired design. Pressure and temperature distributions are also compared. The novel flow field plate structure not only improves the uniformity of reaction gas distribution but also reduces the pressure drop through the flow channels, and the maximum output power of the fuel cell with the novel structure rises by 114% under the same conditions and geometric scale compared to the fuel cell with the parallel flow field.

Lowering the Pressure Drop and Cost of a Proton Exchange Membrane Fuel Cell by Flow Field Plate Design

The flow field plate is a crucial factor affecting the pressure drop and cost of a proton exchange membrane fuel cell (PEMFC). In order to lower the pressure drop and cost of the PEMFC, a novel des...

Optimal design of cathode flow channel for air-cooled PEMFC with open cathode

Air-cooled open-cathode low temperature proton exchange membrane fuel cell (AO-LTPEMFC) with low weight, small volume and compact system has become the new potential power source in the unmanned aerial vehicle (UAV). However, the desirable parameters of the cathode channel are a very important factor to influence the cell performance and the compact of the stack, which have the higher requirements put forward to the structural designs of the cathode channel of AO-LTPEMFC. Thus, some single AO-LTPEMFC fabricated with different width:0.9–1.5 mm, depth:1.1–1.5 mm, ratio (width/landing):1:0.7–1:1.3 and bending:0–10° of the cathode channel was investigated to optimize the cell performance and temperature distribution in the 2 mm plate and determine desirable design parameters. The results show that the different design parameters of the cathode channel affect the contact resistance, oxygen mass transfer of cathode and pressure drop in air flow. For AO-LTPEMFC, to keep the best performance, the cathode channel design parameters should be operated at appropriate width, as deep as possible, small ratio and bending. Through the comparison of various designs, combined with practice process, the optimum design size with width (1.1 mm) × depth (1.3 mm) × width/landing (1:0.7) × bending angel (θ) (5°) was obtained based on the 2 mm thickness of the bipolar plate, which could get the maximum performance and improve the compactness of system. Moreover, analysis in this study will provide a new guideline for the development of cathode flow field plate design in application.

Anode Monitoring By Electrochemical Impedance Spectroscopy in Polymer Electrolyte Membrane Fuel Cells

Although widely used to study the operation of Polymer Exchange Membrane Fuel Cells (PEMFC), Electrochemical Impedance Spectroscopy (EIS) remains a complex tool: experimental data are somewhat delicate to interpret because of the wide range of physical phenomena occurring in Membrane Electrode Assemblies (MEA) and in the flow field plates. Therefore, impedance models are often based on oversimplified equations or conversely, include too many correlated parameters. A typical example of the complexity of the phenomena governing fuel cell electrical behavior are the oscillations of oxygen concentration resulting from the measuring signal, that propagate along the gas channels and makes more difficult the interpretation of the low frequency loop [1, 2, 3]. In addition, most of the impedance models assume Fickian oxygen diffusion although, at least in fuel cells fed with air, Stefan-Maxwell equations should be used as in most stationary models [4, 5]. In this regard, oxygen diffusion and thus the low frequency impedance are strongly dependent on the overall convective flux and as a result, on water management [6].However, due to the characteristic times of oxygen diffusion, these limitations do not apply to the high frequency region of the impedance spectra. The high frequency impedance of a PEMFC remains mostly governed by the cathode [7] but at least in some cases, considering the anode in the Electrical Equivalent Circuit (EEC) is necessary to improve the quality of the fit of the model to the experimental data (Figure). Since the anode has an impact on fuel cell impedance, this means that it becomes possible to monitor its ageing while performing Accelerated Stress Tests (AST). Since most of FC lifetime issues presumably originate from the cathode [8, 9] anode degradation has been rarely studied in the literature. Nevertheless, Schwämmlein et al. showed recently that it may be significant in the case of repeated start-up and shut-down - because of potential cycling - and have a measurable impact on FC performance [10].In this work, we performed AST combining potential and humidity cycles to be as representative as possible of the stressful conditions encountered by the FC in real operating conditions. Commercially available MEA with an initial voltage of the order of 0.7 V at 0.5 A/cm² showed a drop in performance comprised between 400 and 900 µV/h, and a significant degradation of the anode operation was observed by EIS (Figure), confirmed by an increase of its local potentials, and linked to Pt ElectroChemical Surface Area (ECSA) losses. Post-mortem physico-chemical analysis of MEA will be carried out to bridge the decrease of performance with the degradation mechanisms occurring at the anode catalytic layer. Note that these tests were carried out using a 30 cm² segmented cell with 5 straight parallel gas channels [11] (30×1 cm² active area) and that its overall performances may be lower than with regular cells.

Coupled computational fluid dynamics-response surface methodology to optimize direct methanol fuel cell performance for greener energy generation

Optimization of operational parameters is vital for improving the performance of direct methanol fuel cells. To investigate the effects of these parameters on the power density, the experiments were performed using an experimental setup to yield the highest performance. In this regard, response surface methodology (RSM) was applied to select the proper combination of operating variables such as cell temperature, methanol concentration, and oxygen flow rate. Furthermore, a computational fluid dynamics (CFD) model of DMFC flow field plates, including two parallel-serpentine channels with circular bends were conducted using the finite element method at the optimum operating conditions, which obtained by applying RSM. The developed model solves the conservation of charge, mass, momentum, and species (methanol, water, and oxygen) transport equations. The performance tests based on RSM gave the optimum operating conditions as a cell temperature of 70 °C, methanol concentration of 1 M, and an oxygen flow rate of 300 ml/min. The mathematical model in the optimal operating conditions showed that the polarization curve obtained from the modeling study is in good agreement with the experimental data. Also, the concentration distributions of methanol and oxygen at the optimum operating conditions were predicted by the CFD model.

패시브 타입 공랭식 연료전지 성능향상을 위한 캐소드 채널 폭 비율에 대한 수치해석적 연구

In general, a passive air cooled proton exchange membrane fuel cell (PEMFC) operates under an excessive amount of air flow and low humidification conditions, indicating effective control of stack temperature and membrane hydration is of paramount importance for achieving high and stable performance. In this study, we numerically investigate the effects of cathode bipolar plate flowfield design on temperature and water distributions inside a passive air cooled PEMFC. The three-dimensional (3D) non-isothermal PEMFC model is applied to various PEMFC geometries where three different flowfield designs with different ratio and dimensions of air supply channel and cooling channels are taken into account. Simulation results show that the flowfield design with narrow air supply channel and/or wide cooling channel exhibits superior water management performance whereas the effect of oyxgen depletion is minimal due to sufficiently a large amount of air supply conditions. This study clearly demonstrates that the membrane dehydration issue in a passive type air cooled PEMFC can be mitigated by proper design of cathode flowfield.

Flow Field Patterns for Proton Exchange Membrane Fuel Cells

Flow field designs for the bipolar plates of the proton exchange membrane fuel cell are reviewed; including the serpentine, parallel, interdigitated, mesh type or their mixtures, furthermore 2D circular and 3D tubular geometries, porous, fractal and biomimetic flow fields. The advantages / disadvantages and tendencies from field optimizations are discussed. The performance of each flow field design is compared to the conventional serpentine flow field. Good flow field plates give uniform gas distributions, low pressure drop for transport and sufficient rib area to provide high electronic conductivity. A good field should also prevent water condensation, remove water efficiently, and provide sufficiently high moisture content in the membrane. The demands on design are sometimes contradictory. Future work should aim for a flow field geometry and topology that produces uniform gas delivery at a low pressure-drop, and at the same time has an optimal channel shape for better water removal. It is concluded that for an area-filling gas distributor, the developments should aim to find a flow field in accordance with minimum entropy production, making an emphasis on multi-criteria optimization methods.

Fractal-Like Flow-Fields with Minimum Entropy Production for Polymer Electrolyte Membrane Fuel Cells

The fractal-type flow-fields for fuel cell (FC) applications are promising, due to their ability to deliver uniformly, with a Peclet number Pe~1, the reactant gases to the catalytic layer. We review fractal designs that have been developed and studied in experimental prototypes and with CFD computations on 1D and 3D flow models for planar, circular, cylindrical and conical FCs. It is shown, that the FC efficiency could be increased by design optimization of the fractal system. The total entropy production (TEP) due to viscous flow was the objective function, and a constant total volume (TV) of the channels was used as constraint in the design optimization. Analytical solutions were used for the TEP, for rectangular channels and a simplified 1D circular tube. Case studies were done varying the equivalent hydraulic diameter (Dh), cross-sectional area (DΣ) and hydraulic resistance (DZ). The analytical expressions allowed us to obtain exact solutions to the optimization problem (TEP→min, TV=const). It was shown that the optimal design corresponds to a non-uniform width and length scaling of consecutive channels that classifies the flow field as a quasi-fractal. The depths of the channels were set equal for manufacturing reasons. Recursive formulae for optimal non-uniform width scaling were obtained for 1D circular Dh -, DΣ -, and DZ -based tubes (Cases 1-3). Appropriate scaling of the fractal system providing uniform entropy production along all the channels have also been computed for Dh -, DΣ -, and DZ -based 1D models (Cases 4-6). As a reference case, Murray’s law was used for circular (Case 7) and rectangular (Case 8) channels. It was shown, that Dh-based models always resulted in smaller cross-sectional areas and, thus, overestimated the hydraulic resistance and TEP. The DΣ -based models gave smaller resistances compared to the original rectangular channels and, therefore, underestimated the TEP. The DZ -based models fitted best to the 3D CFD data. All optimal geometries exhibited larger TEP, but smaller TV than those from Murray’s scaling (reference Cases 7,8). Higher TV with Murray’s scaling leads to lower contact area between the flow-field plate with other FC layers and, therefore, to larger electric resistivity or ohmic losses. We conclude that the most appropriate design can be found from multi-criteria optimization, resulting in a Pareto-frontier on the dependencies of TEP vs TV computed for all studied geometries. The proposed approach helps us to determine a restricted number of geometries for more detailed 3D computations and further experimental validations on prototypes.

Assessment of the Dynamics Flow Field of Port Plate Pair of an Axial Piston Pump

This paper aims at studying the dynamic fluid evolution process of port plate pair of an axial piston pump. First of all, The Renormalization Group k-ε model (RNG k-ε model) is implemented to simulate the dynamic flow distribution and forecast the evolution of the internal vortex structure inside the valve plate chamber with different speeds of pistons and velocities of inlet fluid by using computational fluid dynamics software. Then, an equivalent amplification test model of a piston-valve plate is built up based on Reynolds similarity theory; the flow state of the piston-valve plate flow field is observed applied the particle image velocimetry (PIV) measuring technique. The resulting uniformity of numerical simulation and PIV measurement verifies that the RNG k-ε model can achieve high-precision prediction for the vortex structure inside the valve plate chamber. Through analysis of velocity contours and streamlines of the flow field, it can be found that vortices with different scales, strengths and positions will occur during the process of fluid distribution, and the scale and strength of the vortex inside the valve plate chamber will be reduced with the increase of the piston’s moving speed, so the energy loss is also reduced and the efficiency is improved.