Interdigitated Gas Distributor Research Articles

3D numerical investigation of clamping pressure effect on the performance of proton exchange membrane fuel cell with interdigitated flow field

Abstract In this work, the performance of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) with interdigitated gas distributor under clamping pressure is numerically studied. A three-dimensional model of PEMFC has been developed and used to study the effect of displacement and deformation caused by clamping pressure on the transport phenomena and device performance. The influence of different parameters such as gas diffusion layer porosity, permeability, thickness, Poisson ratio, and density on the performance of a fuel cell with interdigitated gas distributor on both anode and cathode sides is studied. Obtained results show that there is an optimum range for clamping pressure, caused by assembly force, in which PEMFC performance is in its maximum state. This range depends on the thickness of the gas diffusion layer. The optimum clamping pressures for the thickness of 0.11, 0.254, and 0.37 mm are 395 kPa, 696 kPa, and 1101 kPa, respectively. Furthermore, our findings reveal that the optimum clamping pressure improves the temperature distribution in the fuel cell with the interdigitated flow field. Studying the distribution of water saturation at the cathode catalyst layer demonstrates that the higher the clamping pressure, the lower the water volume fraction and consequently the lower fuel cell performance.

Influence of cathode flow pulsation on performance of proton exchange membrane fuel cell with interdigitated gas distributors

In this paper, a numerical study is conducted in order to investigate the effect of pulsation of air flow at the cathode side of Proton Exchange Membrane (PEM) fuel cell with interdigitated flow field. A two dimensional, isothermal, two-phase, unsteady multi-component transport model is used in order to simulate the transport phenomena. The obtained results are discussed in terms of the influence of flow pulsation on water management and cell performance. The results prove the effectiveness of flow pulsation on improving water removal from cell, enhancing reactants transports to the reaction sites, and increasing the cell performance expressed by increment in the cell limiting current density and maximum output power. The effects of pulsation frequency (f), amplitude (Amp), and mean inlet pressure (Pin) on the performance and the output power of the cell, are also investigated. The performance of the cell has no dependency on the frequency range considered in this study. However, as the pulsation amplitude increases the increment in the cell performance is more obvious. Moreover, applying flow pulsation at low flow rates leads to higher efficiency in water removal and performance enhancement.

Transient Analysis of Proton Electrolyte Membrane Fuel Cells (PEMFC) at Start‐Up and Failure

AbstractA two‐dimensional, transient, single‐phase computational model, incorporating water transport in the membrane and the flow and transport of species in porous gas diffusion electrodes is developed to evaluate the transient performance of a PEMFC with interdigitated gas distributors. The co‐flow and counter‐flow of the anode and cathode reactants are discussed to address their effects on PEMFC performance and transients. The important role of water transport in the membrane on the transients is demonstrated. The membrane's water intake or outtake determines the duration of the transients. The effect of the operating conditions on steady state and transient performances is outlined. Overshoots and undershoots are observed in the average current density, due to a step change in the cell voltage and the cathode pressure under start‐up conditions. Simulation results are used to address the role of auxiliary components in the failure modes of the PEMFC.

Influence of clamping force on the performance of PEMFCs

The objective of the present paper is to investigate the effect of clamping force on the performance of proton exchange membrane fuel cell (PEMFC) with interdigitated gas distributors considering the interfacial contact resistance, the non-uniform porosity distribution of the gas diffusion layer (GDL) and the GDL deformation. The clamping force between the GDL and the bipolar plate is one of the important factors to affect the performance and efficiency of the fuel cell system. It directly affects the structure deformation of the GDL and the interfacial contact electrical resistance, and in turn influences the reactant transport and Ohmic overpotential in the GDL. Finite element method and finite volume method are used, respectively, to study the elastic deformation of the GDL and the mass transport of the reactants and products. It is found that there exists an optimal clamping force to obtain the highest power density for the PEMFC with the interdigitated gas distributors.

Thermal-fluid transports in a five-layer membrane-electrode assembly of a PEM fuel cell

Thermal-fluid transport phenomena in a membrane-electrode assembly (MEA) of a polymer electrolyte membrane (PEM) fuel cell attached to interdigitated gas distributors are studied numerically. The MEA consists of two porous catalyst layers, two porous gas diffusion layers, and an impermeable PEM. In the catalyst layers, the overpotential heating by the electrochemical reaction under thermal equilibrium conditions produces heat that is removed by the fluids as well as the solid matrices. In the diffusion layers, the difference in the heat conductivities between the solid matrices and the fluids causes a thermal non-equilibrium in the porous medium. A two-equation approach is used to resolve the temperature difference between the solid matrices and the fluids. The effects of the porous Reynolds number, interfacial heat transfer coefficient, and overpotential heating are examined. It is found that the local maximum temperature occurs inside the cathodic catalyst layer. In addition, the temperature difference between the solid matrices and the fluids in the diffusion layers decreases with increasing the non-dimensional interfacial heat transfer coefficient. The present results have provided comprehensive heat transfer information that is helpful in understanding of the mechanisms responsible for thermal pathways in a PEM fuel cell.

Comparison of temperature distributions inside a PEM fuel cell with parallel and interdigitated gas distributors

A comparison of the temperature distributions in a proton exchange membrane (PEM) fuel cell between the parallel-flow gas distributors and the interdigitated gas distributor has been discussed in detail. An electrochemical–thermal coupled numerical model in a five-layer membrane-electrode assembly (MEA) is developed. The temperatures for the reactant fuels as well as the carbon fibers in the porous electrode are predicted by using a CFD technique. The overpotential across the MEA is varied to examine its effect on the temperature distributions of the PEM fuel cell. It is found that both the fuel temperature and the carbon fiber temperature are increased with increasing the total overpotential. In addition, the fuel and carbon-fiber temperature distributions are significantly affected by the flow pattern that cast on the gas distributor. Replacing the parallel-flow gas distributor by the interdigitated gas distributor will increase the local maximum temperature inside the PEM fuel cell.

06/02399 A hybrid model of cathode of PEM fuel cell using the interdigitated gas distributor: Liu, X.-L. et al. International Journal of Hydrogen Energy, 2006, 31, (3), 379–389.

06/02399 A hybrid model of cathode of PEM fuel cell using the interdigitated gas distributor: Liu, X.-L. et al. International Journal of Hydrogen Energy, 2006, 31, (3), 379–389.

Predictions of phase temperatures in a porous cathode of polymer electrolyte fuel cells using a two-equation model

In this study, both solid-phase and fluid-phase temperatures inside a porous cathode of a polymer electrolyte fuel cell in contact with an interdigitated gas distributor are predicted numerically. The porous cathode consists of a catalyst layer and a diffusion layer. The heat transfer in the catalyst layer is coupled with species transports via a macroscopic electrochemical model. On the other hand, in the diffusion layer, the energy equations based on the local thermal non-equilibrium (LTNE) are derived to resolve the temperature difference between the solid phase and the fluid phase. As for the species transports, the Bruggemann model is employed to describe the effective diffusivities of the oxygen and water vapor in the porous cathode. Results show that the wall temperature decreases with increasing the intrinsic heat transfer coefficient. As the intrinsic heat transfer coefficients increase, the porous electrode becomes local thermal equilibrium with a strong thermal interaction (heat transfer) between the solid and fluid phases. Under the conditions of high intrinsic heat transfer coefficients, the temperature difference between the solid matrices and the reactant fluids are negligible.

Modeling non-isothermal two-phase multicomponent flow in the cathode of PEM fuel cells

A two-dimensional, non-isothermal, two-phase, multicomponent model is presented for the cathode of a PEM fuel cell, which can be applied using both conventional and interdigitated gas distributors. Gas and liquid transport are described by an extended Darcy’s law using a continuum approach. The most important material properties like wettability, permeability, porosity and tortuosity are determined experimentally. For the determination of the capillary pressure–saturation data, a method based on mercury intrusion porosimetry has been applied. The relative permeability was then derived from this data. It turned out however, that a more detailed description of the partial wetting behaviour of hydrophobic electrodes is of decisive importance. The two-dimensional distribution of the reactants and products is obtained and depends strongly on the flow configuration and the operational conditions. The model results were compared to experimental data and qualitative information on the effects of various operating conditions and on material properties were obtained.

A hybrid model of cathode of PEM fuel cell using the interdigitated gas distributor

A two-dimensional (2D), single- and two-phase, hybrid multi-component transport model is developed for the cathode of PEM fuel cell using interdigitated gas distributor. The continuity equation and Darcy's law are used to describe the flow of the reactant gas and production water. The production water is treated as vapor when the current density is small, and as two-phase while the current density is greater than the critical current density. The advection–diffusion equations are utilized to study species transport of multi-component mixture gas. The Butler–Volmer equation is prescribed for the domain in the catalyst layer. The predicted results of the hybrid model agree well with the available experimental data. The model is used to investigate the effects of operating conditions and the cathode structure parameters on the performance of the PEM fuel cell. It is observed that liquid water appears originally in the cathodic catalyst layer over outlet channel under intermediate current and tends to be distributed uniformly by the capillary force with the increase of the current. It is found that reduction of the width of outlet channel can enhance the performance of PEM fuel cell via the increase of the current density over this region, which has, seemingly, not been discussed in previous literatures.

Heat Transfer in a Porous Electrode of Fuel Cells

The thermal-fluid behaviors in a porous electrode of a proton exchange membrane fuel cell (PEMFC) in contact with an interdigitated gas distributor are investigated numerically. The porous electrode consists of a catalyst layer and a diffusion layer. The heat transfer in the catalyst layer is coupled with species transports via a macroscopic electrochemical model. In the diffusion layer, the energy equations based on the local thermal nonequilibrium (LTNE) are derived to resolve the temperature difference between the solid phase and the fluid phase. Parametric studies include the Reynolds number and the Stanton number (St). Results show that the wall temperature decreases with increasing Stanton number. The maximum wall temperatures occur at the downstream end of the module, while the locations of local minimum wall temperature depend on the Stanton numbers. Moreover, the solid phase and the fluid phase in the diffusion layer are thermally insulated as St⪡1. The diffusion layer becomes local thermal nonequilibrium as the Stanton number around unity. The porous electrode is local thermal equilibrium for St⪢1. Finally, the species concentrations inside the catalyst and diffusion layers are also provided.

Effect of flow orientation on thermal-electrochemical transports in a PEM fuel cell

A non-isothermal model of a proton exchange membrane (PEM) fuel cell in contact with interdigitated gas distributors has been performed. The model accounts for the major transports of convective and diffusive heat and mass transfer, electrode kinetics, and potential fields. The effects of flow orientation and total overpotential across a five-layer membrane-electrode assembly on the thermal behaviors in a PEM fuel cell are examined. A unique feature of the model is the implementation of a thermal-electrochemical algorithm to predict the fluid-phase temperature as well as the solid-matrix temperature in a PEM fuel cell. The simulation results reveal both the solid-matrix temperature and the fluid-phase temperature are increased with increasing total overpotential. Moreover, the fluid-phase and solid-matrix temperature distributions are significantly affected by the flow orientation in the PEM fuel cell. Replacing the parallel-flow geometry by the counter-flow geometry has an advantage of reducing the local maximum temperature inside the fuel cell. Thermal effects on the active material degradation and hence fuel cell durability will be incorporated in the future work.

2D and 3D Modeling of a PEMFC Cathode with Interdigitated Gas Distributors

A steady-state, two-dimensional model of the cathode of a polymer electrolyte membrane fuel cell (PEMFC) with interdigitated gas distributor is formulated with the intention of studying the effects of various operating parameters on its performance. The model describes the fluid dynamics of reactant gases and gives an insight to their distribution in the electrode. The model is verified with published data [ J. S. Yi and T. V. Nguyen , J. Electrochem. Soc. , 146 , 38 (1999) ], but an error has been detected in the data. This work corrects the error, and the results are presented. The effect of changes in electrode permeability, thickness, and shoulder width are then studied. It is observed that changes in permeability, ranging from to , has little impact on the cell performance. Both increasing the electrode thickness and the shoulder width result in poorer performance due to greater resistance to flow. In addition, results show that liquid water tends to form near the outlet of the electrode when the current density is greater than . The 2D model is then extended to a 3D one to determine the flow distribution in a fuel cell for an interdigitated gas distributor. A comparison in performance is made with this 3D model between an interdigitated/conventional gas distributor and it is found that an interdigitated gas distributor does improve cell performance over a conventional gas distributor.

Management of Water Transport in the Cathode of Proton Exchange Membrane Fuel Cells Using Permanent Magnet Particles Deposited in the Cathode-side Catalyst Layer

Recently, it was found that the performance of proton-exchange membrane (PEM) fuel cells was improved by the deposition of small magnet particles in the cathode-side catalyst layer. We developed a numerical simulation to clarify this effect, for a PEM fuel cell equipped with an interdigitated gas distributor. A two-dimensional, two-phase model was used. Cathode electrode consisted of gas diffusion layer and catalyst layer, and the latter was treated as a line. Darcy's law was used to describe the transport of the gas phase. The forces from the shear of the gas flow and of the capillary action move the liquid water through the porous cathode electrode. The magnetic field was modeled by using an equivalent magnetic field. Our numerical results show that the repulsive Kelvin forces acting on liquid water can control the liquid water flow through a porous gas diffusion layer. With increasing residual flux density of magnet particles, the velocity of liquid water near the interface of the catalyst/diffusion layers increases, the saturation of liquid water near the interface decreases, and increasing more pore space is freed for O2 transport and reactions. Therefore, the mechanism of the improvement of the cell performance by magnet particles is clarified using such a numerical model. The use of permanent magnets will be especially useful for portable fuel cell in which there is no power to supply air.

A three-dimensional numerical simulation of the transport phenomena in the cathodic side of a PEMFC

A three-dimensional numerical model is developed to simulate the transport phenomena on the cathodic side of a polymer electrolyte membrane fuel cell (PEMFC) that is in contact with parallel and interdigitated gas distributors. The computational domain consists of a flow channel together with a gas diffusion layer on the cathode of a PEMFC. The effective diffusivities according to the Bruggman correlation and Darcy's law for porous media are used for the gas diffusion layer. In addition, the Tafel equation is used to describe the oxygen reduction reaction (ORR) on the catalyst layer surface. Three-dimensional transport equations for the channel flow and the gas diffusion layer are solved numerically using a finite-volume-based numerical technique. The nature of the multi-dimensional transport in the cathode side of a PEMFC is illustrated by the fluid flow, mass fraction and current density distribution. The interdigitated gas distributor gives a higher average current density on the catalyst layer surface than that with the parallel gas distributor under the same mass flow rate and cathode overpotential. Moreover, the limiting current density increased by 40% by using the interdigitated flow field design instead of the parallel one.

Design and optimization of polymer electrolyte membrane (PEM) fuel cells

The performance of polymer electrolyte membrane (PEM) fuel cells is studied using a single-phase two-dimensional electrochemical model. The model is coupled with a nonlinear constrained optimization algorithm to determine an optimum design of the fuel cell with respect to the operation and the geometrical parameters of cathode such as the air inlet pressure, the cathode thickness and length and the width of shoulders in the interdigitated air distributor. In addition, the robustness of the optimum design of the fuel cell with respect to uncertainties in several electrochemical reaction and species transport parameters (e.g., gas diffusivity, agglomerate particle size, etc.) is tested using a statistical sensitivity analysis. The results of the optimization analysis show that higher current densities at a constant cell voltage are obtained as the inlet air pressure and the fraction of the cathode length associated with a shoulder of the interdigitated air distributor are increased, and as the cathode thickness and the length of the cathode per one interdigitated gas distributor shoulder are decreased. The statistical sensitivity analysis results, on the other hand, show that the equilibrium cathode/membrane potential difference has the largest effect on the predicted polarization curve of the fuel cell. However, the optimal design of the cathode side of the fuel cell is found not to be affected by the uncertainties in the model parameters such as the equilibrium cathode/membrane potential difference. The results obtained are rationalized in terms of the effect of the fuel-cell design on the air flow fields and the competition between the rates of species transport to and from the cathode active layer and the kinetics of the oxygen reduction half-reaction.

Two‐phase flow model of the cathode of PEM fuel cells using interdigitated flow fields

AbstractWhen interdigitated gas distributors are used in a PEM fuel cell, fluids entering the fuel cell are forced to flow through the electrodes porous layers. This characteristic increases transport rates of the reactants and products to and from the catalyst layers and reduces the amount of liquid water entrapped in the porous electrodes thereby minimizing electrode flooding. To investigate the effects of the gas and liquid water hydrodynamics on the performance of an air cathode of a PEM fuel cell employing an interdigitated gas distributor, a 2‐D, two‐phase, multicomponent transport model was developed. Darcy's law was used to describe the transport of the gas phase. The transport of liquid water through the porous electrode is driven by the shear force of gas flow and capillary force. An equation accounting for both forces was derived for the liquid phase transport in the porous gas electrode. Higher differential pressures between inlet and outlet channels yield higher electrode performance, because the oxygen transport rates are higher and liquid water removal is more effective. The electrode thickness needs to be optimized to get optimal performance because thinner electrode may reduce gas‐flow rate and thicker electrode may increase the diffusion layer thickness. For a fixed‐size electrode, more channels and shorter shoulder widths are preferred.

Multicomponent Transport in Porous Electrodes of Proton Exchange Membrane Fuel Cells Using the Interdigitated Gas Distributors

Hydrodynamics of gases in the cathode of a proton exchange membrane fuel cell that is contacted to an interdigitated gas distributor are investigated using a steady‐state multicomponent transport model. The model describes the two‐dimensional flow patterns and the distributions of the gaseous species in the porous electrode and predicts the current density generated at the electrode and membrane interface as a function of various operating conditions and design parameters. Results from the model show that, with the forced flow‐through condition created by the interdigitated gas distributor design, the diffusion layer is greatly reduced. However, even with a much thinner diffusion layer, diffusion still plays a significant role in the transport of oxygen to the reaction surface. The results also show that the average current density generated at an air cathode increases with higher gas flow‐through rates, thinner electrodes, and narrower shoulder widths between the inlet and outlet channels of the interdigitated gas distributor. © 1999 The Electrochemical Society. All rights reserved.