Flow rate and humidification effects on a PEM fuel cell performance and operation (original) (raw)
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A full three-dimensional, non-isothermal computational fluid dynamics model of a proton exchange membrane (PEM) fuel cell with straight flow field channels has been developed. This comprehensive model accounts for the major transport phenomena in a PEM fuel cell: convective and diffusive heat and mass transfer, electrode kinetics, and potential fields. The new feature of the algorithm developed in this work is its capability for accurate calculation of the local activation overpotentials, which in turn results in improved prediction of the local current density distribution. The model is shown to be able to understand the many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. This model is used to study the effects of several operating, design, and material parameters on fuel cell performance. Detailed analyses of the fuel cell performance under various operating conditions have been conducted and examined. The analysis helped identifying critical parameters and shed insight into the physical mechanisms leading to a fuel cell performance under various operating conditions. r
Energy Conversion and Management, 2007
This paper presents the results of an optimization study using a comprehensive three-dimensional, multi-phase, non-isothermal model of a PEM fuel cell that incorporates the significant physical processes and the key parameters affecting fuel cell performance. The model accounts for both the gas and liquid phase in the same computational domain and, thus, allows for the implementation of phase change inside the gas diffusion layers. The model includes the transport of gaseous species, liquid water, protons, energy and water dissolved in the ion conducting polymer. Water is assumed to be exchanged among three phases; liquid, vapor and dissolved, and equilibrium among these phases is assumed. The model features an algorithm that allows a more realistic representation of the local activation overpotentials, which leads to improved prediction of the local current density distribution. This model also takes into account convection and diffusion of different species in the channels as well as in the porous gas diffusion layer, heat transfer in the solids as well as in the gases and electrochemical reactions. The results showed that the present multi-phase model is capable of identifying important parameters for the wetting behavior of the gas diffusion layers and can be used to identify conditions that might lead to the onset of pore plugging, which has a detrimental effect on the fuel cell performance. This model is used to study the effects of several operating, design and material parameters on fuel cell performance. Detailed analyses of the fuel cell performance under various operating conditions have been conducted and examined.
Asia-Pacific Journal of Chemical Engineering, 2009
Abstract The aim of this paper is to present a simple 3D computational model of a polymer electrolyte membrane fuel cell (PEMFC) that simulates over time the heat distribution, energy, and mass balance of the reactant gas flows in the fuel cell including pressure drop, humidity, and liquid water. Although this theoretical model can be adapted to any type of PEMFC, for verification of the model and to present different analysis it has been adapted to a single cell test fixture. The model parameters were adjusted through a series of ...
SpliTech, 2023
Proton exchange membrane fuel cells are gaining momentum in the automotive sector due to their favorable characteristics such as quick refueling times, silent operation, high efficiency, and clean energy production with only byproducts being heat and water. In this study, numerical models are developed using state-of-the-art Computational Fluid Dynamics modeling software for full-scale single PEM (Proton Exchange Membrane) fuel cells with different flow fields. Commonly, for small-scale fuel cells, such as 25 cm2, single serpentine is used for operation. The objective of this work was to see if the performance can be enhanced by increasing the number of channels, while it was also important to keep the dimensions of the channels feasible for manufacturing using CNC (Computer Numerical Control) milling and the available drill bit sizes. The number of channels was increased from one to three and the relative humidity of the reactants was set to partially and fully humidified. The results of the simulations indicate a considerable difference in the performance of the cells on elevated current densities, especially for the cases with lower relative humidity. The results of this study outline the requirement for the development of a standardized flow field for testing small active area single cells in the future.
Journal of Power Sources, 2000
The purpose of this work was the enhancement of performance of Polymer Electrolyte Membrane Fuel Cells PEMFC by optimising the gas flow distribution system. To achieve this, 3D numerical simulations of the gas flow in the assembly, consisting of the fuel side of Ž. the bipolar plate and the anode, were performed using a commercial Computational Fluid Dynamics CFD software, the ''FLUENT'' package. Two types of flow distributors were investigated: a grooved plate with parallel channels of the type commonly used in commercial fuel cells, and a porous material. The simulation showed that the permeability of the gas flow distributor is a key parameter affecting the consumption of reactant gas in the electrodes. Fuel utilisation increased when decreasing the permeability of the flow distributor. In particular, fuel consumption increased significantly when the permeability of the porous material decreased to values below that of the anode. This effect was not observed in the grooved plate, which permeability was higher than that of the anode. Even though the permeability of the grooved plate can be diminished by reducing the width of the channels, values lower than 1 mm are difficult to attain in practice. The simulation shows that porous materials are more advantageous than grooved plates in terms of reactant gas utilisation.
Advanced computational tools for PEM fuel cell design
Journal of Power Sources, 2008
This paper reports on the systematic experimental validation of a comprehensive 3D CFD-based computational model presented and documented in Part 1. Simulations for unit cells with straight channels, similar to the Ballard Mk902 hardware, are performed and analyzed in conjunction with detailed current mapping measurements and water mass distributions in the membrane-electrode assembly. The experiments were designed to display sensitivity of the cell over a range of operating parameters including current density, humidification, and coolant temperature, making the data particularly well suited for systematic validation. Based on the validation and analysis of the predictions, values of model parameters, including the electro-osmotic drag coefficient, capillary diffusion coefficient, and catalyst specific surface area are determined adjusted to fit experimental data of current density and MEA water content. The predicted net water flux out of the anode (normalized by the total water generated) increases as anode humidification water flow rate is increased, in agreement with experimental results. A modification of the constitutive equation for the capillary diffusivity of water in the porous electrodes that attempts to incorporate the experimentally observed immobile (or irreducible) saturation yields a better fit of the predicted MEA water mass with experimental data. The specific surface area parameter used in the catalyst layer model is found to be effective in tuning the simulations to predict the correct cell voltage over a range of stoichiometries.
Numerical Investigation of Channel Geometry on the Performance of a Pem Fuel Cell
International Journal of Applied Mechanics and Engineering, 2000
A complete three-dimensional and single phase model for proton exchange membrane (PEM) fuel cells is used to investigate the effect of using different channels geometry on the performances, current density and gas concentration. The proposed model is a full cell model, which includes all the parts of the PEM fuel cell, flow channels, gas diffusion electrodes, catalyst layers and the membrane. Coupled transport and electrochemical kinetics equations are solved in a single domain; therefore no interfacial boundary condition is required at the internal boundaries between cell components. This computational fluid dynamics code is used as the direct problem solver, which is used to simulate the three-dimensional mass, momentum, energy and species transport phenomena as well as the electron-and proton-transfer process taking place in a PEMFC. The results show that the predicted polarization curves by using this model are in good agreement with the experimental results and a high performance was observed by using circle geometry for the channels of anode and cathode sides. Also the results show that the performance of the fuel cell improved by using the rectangular channel than the elliptical and triangular channels.
The development of physically representative models that allow reliable simulation of the processes under realistic conditions is essential to the development and optimization of fuel cells, the introduction of cheaper materials and fabrication techniques, and the design and development of novel architectures. Full three-dimensional, multiphase, non-isothermal computational fluid dynamics models of planar airbreathing and airflow-channel PEM fuel cell have been developed. These comprehensive models account for the major transport phenomena in both these types: convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields. The models are shown to understand the many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. Fully three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented and analyzed with a focus on the physical insight and fundamental understanding for the air-breathing and airflowchannel PEM fuel cells.
Analysis of PEM (Polymer Electrolyte Membrane) fuel cell cathode two-dimensional modeling
The performance of PEMFC (Polymer Electrolyte Membrane Fuel Cells) with different configuration of gas feeding channels is investigated. Multi-component mixture model is used in order to simulate the two phase flow and transport in cathode gas diffusion layer of PEM fuel cell. This model reduces the numerical simulation complexity by reducing the number of nonlinear governing equations. A wide detailed parametric study is done to investigate different operational parameter such as; pressure difference , operating temperature, different geometrical parameters such as; gas diffusion layer thickness, and various material parameters such as porosity and wettability. Computational simulations have been conducted and the simulation results were compared with the available results in literature and showed very little difference. Results have been presented with different polarization curves, power density and local current density curves and also the plots of saturation level at catalyst layer surface. Furthermore the changes in the place of the interface between single and two phase zones is presented for further understating of the effects of different parameters. This parametric study confirms qualitatively to the validity of the considered model for systematic simulation of the PEM fuel cells.