Flow Field Plate Research Articles

Influence of Compressive Stress on the Water Content of Perfluorosulphonated Membranes: A μ‐Raman Study

AbstractThe effect of compressive stress on the local water content of Nafion NRE 212 and Aquivion E79 membranes is studied by confocal μ‐Raman spectroscopy using a specific tightening device. This device aims to mimic the geometry of the bipolar plate flow field of actual fuel cells, i.e. the sequence of channels and ribs. The membrane water content decreases with increasing stress, under the ribs as well as in the channel. The higher the initial water content, the larger the water content decreases with mechanical stress. The extent of water loss depends on the position of the membrane in the device, the applied stress and the hydration history of the membrane.

Measurement of current distribution in a proton exchange membrane fuel cell with various flow arrangements – A parametric study

Understanding of current distributions in proton exchange membrane fuel cells (PEMFCs) is crucial for designing cell components such as the flow field plates and the membrane electrode assembly (MEA). In this study, the spatial current density distributions in a single PEMFC with three serpentine flow channels are measured using a segmented bipolar plate and printed circuit board technique. The effects of key operating conditions such as stoichiometry ratios, inlet humidity levels, cell pressure and temperature on the local current density distributions for co-, counter-, and cross-flow arrangements are examined. It is observed that the local current density distribution over the MEA is directly affected by the cell operating conditions along with the configuration of the flow arrangement. It is also found that among the different flow configurations tested under the various operating conditions, the counter flow arrangement provides the optimum average current density and the lowest variations in the local current densities along the flow channels.

Performance Analysis on Planar Micro PDMS Proton Exchange Membrane Fuel Cell Stack

The objective of this study is to develop a micro proton exchange membrane fuel cell (PEMFC) stack, in which a flow field plate in each cell is made of polydimethyl-siloxane (PDMS) and manufactured by micro-molding technology. A four-cell micro PEMFC stack in series with a volume of 12 cm × 4.5 cm × 1.2 cm is constructed and tested. The active area of a membrane electrode assembly (MEA) is 2 cm × 2 cm in each individual PEMFC, and the platinum loadings at anode and cathode are 0.3 and 0.5 mg/cm^2, respectively. A series of performance experiments were carried out. Experimental parameters included clamping force and fuel supply condition. Durability tests were carried out as well. Experimental results showed that an appropriate clamping torque range should be considered carefully to enhance performance without narrowing down fuel flow channels. Under a torque of 2.0 kgf•cm, peak power density for this stack is 122.5 mW/cm^2 at 2.0 V. Increase in fuel flow rate is not the best way to improve concentration polarization in this air-breathing stack experiment because of limited air supply, and each cell in the same stack has a different performance under the present arrangement. At present, such stack can maintain a stable power output for a long time (up to 14 hours).

A numerical investigation of the effects of GDL compression and intrusion in polymer electrolyte fuel cells (PEFCs)

The purpose of this work is to numerically investigate the effects of non-uniform compression of the gas diffusion layer (GDL) and GDL intrusion into a channel due to the channel/rib structure of the flow-field plate. The focus is placed on accurately predicting two-phase transport between the compressed GDL near the ribs and uncompressed GDL near the channels, and its associated effects on cell performance. In this paper, a GDL compression model is newly developed and incorporated into a comprehensive three-dimensional, two-phase PEFC model developed earlier. To assess solely the effects of GDL compression and intrusion, the new fuel cell model is applied to a simple single-straight channel fuel cell geometry. Numerical simulations with different levels of GDL compression and intrusion are carried out and simulation results reveal that the effects of GDL compression and intrusion considerably increase the non-uniformity, particularly, the in-plane gradient in liquid saturation, oxygen concentration, membrane water content, and current density profiles that in turn results in significant ohmic and concentration polarizations. The present three-dimensional GDL compression model yields realistic species profiles and cell performance that help to identify the optimal MEA, gasket, and flow channel designs in PEFCs.

Numerical Simulation of a Novel Bipolar Plate Flow Field of Proton Exchange Membrane Fuel Cell

This paper proposes a novel bipolar plate flow field of PEMFC with the intersectant microstructure. Numerical simulation about both the flow velocity distribution and the pressure distribution for the reactive gas were accomplished according to the model building by Pro/E, grid meshing and boundary condition specifying by Fluent. Compared to traditional serpentine flow fields, the gas pressure difference between the inlet and the outlet of this novel flow field is appropriate to promptly discharge the water produced during the operation of the PEMFC, and the flow velocity of the reactive gas among all the flow field is well-distributed, which assures reactions occurring uniformly in the flow field under the bipolar plate. All the properties of this novel flow field make a great sense to improve the integrated performance of the PEMFC.

Application of water barrier layers in a proton exchange membrane fuel cell for improved water management at low humidity conditions

This study discusses the use of an additional layer in the cathode side of a proton exchange membrane fuel cell (PEMFC) for improved water management at dry conditions. The performance of fuel cells deteriorates significantly when low to no gas humidification is used. This study demonstrates that adding a non-porous material with perforations, such as stainless steel, between the cathode flow field plate and the gas diffusion layer (GDL) improves the water saturation in the cathode GDL and catalyst layer, increases the water content in the anode, and keeps the membrane hydrated. The slight voltage drop in the performance as a result of transport limitations is justifiable since the overall durability of the cell at these extreme conditions is enhanced. The results show that the perforated layer(s) enhances the operational life of the PEMFC under completely dry conditions. These extreme conditions (dry gases without humidification, 90 kPa, 75 °C) were used to accelerate the failure modes in the fuel cells.

Effects of difference flow channel designs on Proton Exchange Membrane Fuel Cell using 3-D Model

Abstract This research was studied to design of flow field on Proton Exchange Membrane Fuel Cell for distributions in reaction gas. The design of flow field was studied the effects of channel configurations of flow field plates on the performance of a PEMFC. Effects of widths, length and curve channel of a flow field plate were studied in an effort to optimize the dimensions of channel. It was assumed that the development of these design techniques with CFD will require. This study used three-dimensional computational fluid dynamics (CFD) model was investigated the effects of serpentine flow channel designs on the performance of proton exchange membrane fuel cells. This model was validated by the experiments. The numerical results were provided understanding the effect of flow field pattern design on performance of the fuel cell. This led us to a better design of gas flow field, which improves the gas distribution and water management. This research will investigate the relationship between channel length, channel curvature and characteristics of flow field with pressure drop, velocity distribution by using numerical model. The experiments will performed to verify the numerical predictions on polarization curve and power curve. The output from this research will enlight our on fundamental knowledge, which can be applied on design and operate the fuel cell.

Production of Ni-P Amorphous Alloy-Coated Bipolar Plate for PEM Fuel Cell by Electro-Less Plating

In this work, electro-less plating was adopted to produce a new metallic bipolar plate coated with amorphous alloy. The Ni-P amorphous alloy thin film was deposited on Al plate with a bipolar plate flow field and its corrosion resistance and contact electrical resistance were measured. As results, it was found that the electro-less plated Ni-P amorphous thin film showed much lower corrosion resistance than the Ni-Cr-P-B metallic glass because of its lack of Cr content and also found that the Ni-P film showed lower contact electrical resistance than the stainless steel SUS316L plate.The electricity generation tests with the single cell having the Ni-P amorphous alloy-coated bipolar plates produced in this study revealed that the single cell with the Ni-P amorphous alloy-coated bipolar plates showed excellent I-V performance as well as the cell with the carbon bipolar plates after 39th repetition. However, the I-V performance degraded gradually and was found to be much lower than that with the carbon bipolar plates after 50th repetition. Then the long time durability tests for 24 h were also conducted at the constant current density of 200 mA·cm−2. It was found that the cell voltage of the single cell with the Ni-P amorphous alloy-coated bipolar plates decreased gradually with time.

無電解めっき法を用いたNi-Pアモルファス合金被覆燃料電池用セパレータの作製

In this work, electro-less plating was adopted to produce a new metallic bipolar plate coated with amorphous alloy. The Ni-P amorphous alloy thin film was deposited on Al plate with a bipolar plate flow field and its corrosion resistance and contact electrical resistance were measured. As results, it was found that the electro-less plated Ni-P amorphous thin film showed much lower corrosion resistance than the Ni-CrP-B metallic glass because of its lack of Cr content and also found that the Ni-P film showed lower contact electrical resistance than the stainless steel SUS316L plate. The electricity generation tests with the single cell having the Ni-P amorphous alloy-coated bipolar plates produced in this study revealed that the single cell with the Ni-P amorphous alloy-coated bipolar plates showed excellent I-V performance as well as the cell with the carbon bipolar plates after 39th repetition. However, the I-V performance degraded gradually and was found to be much lower than that with the carbon bipolar plates after 50th repetition. Then the long time durability tests for 24 h were also conducted at the constant current density of 200 mAcm 2 . It was found that the cell voltage of the single cell with the Ni-P amorphous alloy-coated bipolar plates decreased gradually

Optimum design of the slotted-interdigitated channels flow field for proton exchange membrane fuel cells with consideration of the gas diffusion layer intrusion

The design of the flow field greatly affects the flow distribution and the final performance of the proton exchange membrane fuel cell (PEMFC) system. The clamping force between the gas diffusion layer (GDL) and the flow field plate (FFP) will cause the inhomogeneous compression of the GDL. Then the GDL will be intruded into the reactant gas channels and eventually change the flow distribution. This paper presents a study on the effect of the intrusion of the GDL on the flow field in a PEMFC, and tries to explain the reason for poor performance of the previous design of the flow field other than those have been studied in other papers such as GDL roughness, porosity, etc. First of all, a linear analytical model is used to analyze the sensitivities of the flow field to the GDL intrusion, and then used to estimate the effect of the GDL intrusion on the flow field distribution. Secondly, a multi-objective optimization model is proposed to eliminate the nonuniform distribution in the flow field with the GDL intrusion taken into consideration. Subsequently, three different designs are analyzed and compared with each other as a demonstration to show the effect of the GDL intrusion. From the analysis results, it is recommended that the effect of the GDL intrusion on the multi-depth flow field should be taken into consideration and the flow field should be insensitive to the GDL intrusion to obtain high robust performance. The results obtained in the study provide the designer some useful guidelines in the concept design of flow field configurations.

Experimental study on the effect of reactant flow arrangements on the current distribution in proton exchange membrane fuel cells

Current distribution in a proton exchange membrane fuel cell (PEMFC) is significantly influenced by reactant flow configurations. In this study, the current distribution has been measured experimentally using a segmented flow-field plate and printed circuit board (PCB). Local current distributions for a PEMFC with serpentine flow field and three different flow arrangements including co-flow, cross-flow, and counter-flow arrangements for the anode and cathode streams are investigated along with the effect of flow channel orientation. It is shown that the counter-flow arrangement yields most uniform distribution for the current density, whereas the co-flow arrangement results in a considerable variation in the current density from the reactant gas stream inlet to exit. Flow channel orientation can also impact the cell performance and the current distribution appreciably. The limiting hydrogen concentration at the anode side due to the low stoichiometry condition can have a predominant effect on the current distribution and cell performance.

Polymer Electrolyte Membrane Fuel Cell (PEMFC) Flow Field Plate: Design, Materials and Characterisation

AbstractThis review describes some recent developments in the area of flow field plates (FFPs) for proton exchange membrane fuel cells (PEMFCs). The function, parameters and design of FFPs in PEM fuel cells are outlined and considered in light of their performance. FFP materials and manufacturing methods are discussed and current in situ and ex situ characterisation techniques are described.

Two-Dimensional Property Distributions, Ohmic Losses, and Power Consumption within a Fuel Cell Polymer Electrolyte Membrane

The average and localized water content, current, ohmic loss, and power consumption distributions within a Nafion 117 polymer electrolyte membrane (PEM) were modeled in two dimensions to determine the influence of the cathodic flowfield plate on the properties and performance of a fuel cell. The membrane model was decoupled from the cathode and anode by using fixed, assumed anodic boundary conditions and cathodic boundary conditions from literature indicative of operation at three channel:land configurations (1:1, 2:1, and 4:1) and three nominal cathode overpotentials (NCOs) (0.3, 0.5, and 0.7 V). The results suggested that a 1:1 configuration maintained the membrane in a more-hydrated state that was better able to moderate changes in ohmic loss and power consumption due to changes in the NCO. Detailed distributions within the membrane showed complex anisotropy, including the existence of localized maxima along anodic boundaries, cathodic boundaries, and even along both anodic and cathodic boundaries unde...

Stainless Steel Bipolar Plates for PEM Fuel Cell

The corrosion resistance of several metallic materials was evaluated in the chemical environment encountered in PEM fuel cells. The value of PREN (Pitting Resistance Equivalent Number) was calculated for metallic materials and compared whit the corrosion current. PREN is not useful in bipolar plates research. Merely SS 316 and Inconel 625 are suitable for use as a flow-field plate on the cathodic side of a PEM fuel cell. Inconel 625 has a higher CR, because of its Mo content. The corrosion resistance of AISI 444 is acceptable as material for bipolar plate materials. The corrosion resistance of SS 7222 is higher and cannot been considered as material for bipolar plate materials.

Numerical modeling of three-dimensional two-phase gas–liquid flow in the flow field plate of a PEM electrolysis cell

Numerical simulations were performed for three-dimensional two-phase water/oxygen flow in the flow field plate at the anode side of a PEM electrolysis cell. The mixture model was used to simulate two phases for the purpose of examining flow features in the flow field plate in order to effectively guide the design of electrolysis cells. The water flow rate was maintained as a constant of 260 mL/min, while the flow rate of oxygen generation was assumed to change from 0 to 14 mg/s. The obtained results including the velocity, pressure, and volume fraction distributions are presented and discussed. It is found that the obtained results for single-phase flow cases cannot be linearly extrapolated into the two-phase flow cases. The irregular velocity profile (locally low velocity magnitude near the exit port section) is not observed when the flow rate of oxygen generation is relatively low. As the mass flow rate of oxygen generation increases, reverse flow develops inside the flow channels.

A study of multi-phase flow through the cathode side of an interdigitated flow field using a multi-fluid model

This work presents a study of multi-phase flow through the cathode side of a polymer electrolyte membrane fuel cell employing an interdigitated flow field plate. A previously published model has been extended in order to account for phase change kinetics, and a comparison between the interdigitated flow field design and a conventional straight channel design has been conducted. It is found that the parasitic pressure drop in the interdigitated design is in the range of a few thousand Pa and could be reduced to a few hundred Pa by choosing diffusion media with high in-plane permeability. The additional compressor work due to the increased pressure loss will only slightly increase, and this may be offset by operating at lower stoichiometries as the interdigitated design is less mass transfer controlled, which means that the overall efficiency of the interdigitated arrangement will be higher. In the interdigitated design more product water is carried out of the cell in the vapor phase compared to the straight channel design which indicates that liquid water management might be less problematic. This effect also leads to the finding that in the interdigitated design more waste heat is carried out of the cell in the form of latent heat which reduces the load on the coolant. Finally we see that the micro-porous layer might help keep the gas diffusion layer substrate dry due to a potentially higher evaporation rate caused by a combination of the Kelvin effect and a larger specific surface area compared to the diffusion layer substrate.

Study on Electrical Conductivity and Mechanical Performance of Polymeric Composite Flow Field Plates for Fuel Cell Applications

Fuel cell technology has received a great deal of attention as a candidate for an alternative power source due to its environmental benefits compared to conventional sources. Flow-field plates are one of the most important components of the Proton Exchange Membrane (PEM) and Direct Methanol (DM) fuel cells technology, which is expected to possess high electrical and thermal conductivity, low hydrogen permeability, and good mechanical performance. In this study, a systematic investigation was carried out to formulate and fabricate electrically conductive polymer composites to be used in production of flow field plates using a simple low temperature, single step moulding process. It focused on the careful selection of both materials and processing methodology. ElectroPhen™ binders, various concentrations of graphite powder and enhanced dispersion agents were employed to make composite plates with high electrical conductivity and satisfactory mechanical performance. Electrical conductivity measurements were carried out using purpose-built in-plane and through-plane electrical conductivity test kits. Flexural tests were carried out to evaluate the mechanical performance of the composites. It has been found that polymer composite flow field plates can attain the electrical conductivity and mechanical performance requirements for commercial fuel cell applications without requiring a high temperature multi-step production process.

Production of Ni<SUB>65</SUB>Cr<SUB>15</SUB>P<SUB>16</SUB>B<SUB>4</SUB> Metallic Glass-Coated Bipolar Plate for Fuel Cell by High Velocity Oxy-Fuel (HVOF) Spray Coating Method

In this study, the newly designed bipolar plate for proton exchange membrane fuel cells (PEMFC) was produced by spray-coating the Ni65Cr15P16B4 metallic glassy alloy on Al plate. The Ni65Cr15P16B4 metallic glass was adopted as a coating material because of its excellent corrosion resistance and the high velocity oxy-fuel (HVOF) spray coating was used for the metallic glass deposition on the Al plates having a bipolar plate flow field. The corrosion resistance of the Ni65Cr15P16B4 glassy alloy film produced by the HVOF spray-coating was studied under simulated PEMFC environments. As a result, the Ni65Cr15P16B4 glassy alloy film showed lower corrosion current density than the high-corrosion-resistant stainless steel SUS316L. Then, the electricity generation tests with the single cell having the Ni65Cr15P16B4 glassy alloy-coated bipolar plates produced in this study were conducted. As a result, the single cell with the metallic glass-coated bipolar plates showed very high I-V performance as well as the cell with the carbon bipolar plates. The long time durability tests for 24 h were also conducted at the constant current density of 200 mAcm 2 . As a result, the single cell with the glass-coated bipolar plates showed no voltage drop during the test. So, it was found in this study that the Ni65Cr15P16B4 glassy alloy-coated bipolar plate produced by the HVOF spray-coating have a potential for practical use for the fuel cells. [doi:10.2320/matertrans.MAW201006]

A novel scheme for precise diagnostics and effective stabilization of currents in a fuel cell stack

A novel scheme for detecting inhomogeneous internal currents in a fuel cell stack is presented. In this paper the scheme is investigated for the case that the flow field plates consist of graphite. Then plates of high conductivity, e.g. aluminium between the flow field plates together with small slits in these plates have three effects: (a) Whenever a local inhomogeneity of the electric current occurs at a particular cell in the stack, this will induce a surface current close to that cell perpendicular to the averaged current. This current can be detected. (b) The plates of high conductivity completely prevent the inhomogeneities from spreading to neighbouring cells. (c) Even at the particular cell the inhomogeneity is suppressed as far as possible. Thus this scheme leads to much better diagnostic possibilities and at the same time reduces electric instabilities to an extent, where they probably become harmless. This scheme will first be explained for a simple model to clarify the idea. However, very precise three dimensional computations using realistic parameters are presented, corroborating the results of the simple model. Copyright © 2009 John Wiley & Sons, Ltd.

In situ-polymerized wicks for passive water management in proton exchange membrane fuel cells

Air-delivery is typically the largest parasitic loss in PEM fuel cell systems. We develop a passive water management system that minimizes this loss by enabling stable, flood-free performance in parallel channel architectures, at very low air stoichiometries. Our system employs in situ-polymerized wicks which conform to and coat cathode flow field channel walls, thereby spatially defining regions for water and air transport. We first present the fabrication procedure, which incorporates a flow field plate geometry comparable to many state-of-the-art architectures (e.g., stamped metal or injection molded flow fields). We then experimentally compare water management flow field performance versus a control case with no wick integration. At the very low air stoichiometry of 1.15, our system delivers a peak power density of 0.68 W cm −2. This represents a 62% increase in peak power over the control case. The open channel and manifold geometries are identical for both cases, and we demonstrate near identical inlet-to-outlet cathode pressure drops at all fuel cell operating points. Our water management system therefore achieves significant performance enhancement without introducing additional parasitic losses.