A Novel Reactant Delivery System for PEM Fuel Cells

2008 ◽  
Author(s):  
Brenton Greska ◽  
Peter DeRoche ◽  
Anjaneyulu Krothapalli
Keyword(s):  
Fuel Cell ◽  
Relative Humidity ◽  
Pem Fuel Cells ◽  
Operating Conditions ◽  
Polarization Curves ◽  
Delivery Method ◽  
Supply Pressure ◽  
Flow Channels ◽  
Air Supply ◽  
Cell Test

This paper deals with the use of microjets as a reactant delivery method for a PEM fuel cell. The flow physics of this technique have been adapted such that an even distribution of reactants over the membrane is achieved. A single cell based on this microjet delivery method has been built and tested using the fuel cell test station at SESEC. Polarization curves were obtained for a number of different operating conditions in which the relative humidity and supply pressure of the air supply were varied. Similar operating conditions were used to obtain polarization curves for a similarly sized commercially available fuel cell that utilizes commonly used serpentine flow channels for reactant delivery. Comparison of the polarization curves at similar operating conditions revealed that the microjet-based fuel cell was relatively unaffected by the changes in relative humidity and and positively affected by an increase in supply pressure, which was in stark contrast to what was observed for the commercial fuel cell.

Simulation-Aided PEM Fuel Cell Design and Performance Evaluation

2004 ◽  
Vol 2 (1) ◽  
pp. 20-28 ◽  
Author(s):  
Junxiao Wu ◽  
Qingyun Liu
Keyword(s):  
Fuel Cell ◽  
Catalyst Layer ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Operating Conditions ◽  
Half Cell ◽  
Flow Channels ◽  
Simulation Strategy ◽  
Cell Simulation ◽  
And Performance

A multi-resolution fuel cell simulation strategy has been employed to simulate and evaluate the design and performance of hydrogen PEM fuel cells with different flow channels. A full 3D model is employed for the gas diffusion layer and a 1D+2D model is applied to the catalyst layer. Further, a quasi-1D method is used to model the flow channels. The cathode half-cell simulation was performed for three types of flow channels: serpentine, parallel, and interdigitated. Simulations utilized the same overall operating conditions. Comparisons of results indicate that the interdigitated flow channel is the optimal design under the specified operating conditions.

A Study of Water and Oxygen Distributions in the Cathode Flow Channels of a PEM Fuel Cell

2006 ◽  
Author(s):  
Han-Sang Kim ◽  
Taehun Ha ◽  
Kyoungdoug Min
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Water Saturation ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Experimental Results ◽  
Fuel Cell Performance ◽  
Flow Channels

Water management is a critical operation issue for achieving the highest possible performance of proton exchange membrane (PEM) fuel cells. Quantitative determination of water and species distribution is needed to understand the water management and reactant distribution effects. In this study, the measurement of water and oxygen distributions along cathode flow channels was carried out using gas chromatography (GC). Generally, it is difficult to measure water distribution where water concentration is too high. Here, the measurement of high levels of water saturation in cathode channels was performed according to fuel cell operating conditions. GC measurement was also carried out for flooding and non-flooding conditions. To compare the experimental results with computational results, the three-dimensional CFD simulation of a unit fuel cell was performed using es-pemfc, which is the PEM fuel cell module of commercial CFD code STAR-CD. For the entrance of flow channel that has relatively lower level of water content, the calculated results showed good agreement with measured results. However, some discrepancy between calculated and experimental results was still found for the flow channels near the cathode outlet. The study provides the necessity of the development and adoption of a comprehensive multidimensional PEM fuel cell models including two-phase flow and cathode flooding phenomena for the optimization of fuel cell performance.

Comparative Investigation on Waste Heat Driven Air Supply Systems for PEM Fuel Cells

2016 ◽  
Author(s):  
Lili Yu ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Jie Peng
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Waste Heat ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Stoichiometric Ratio ◽  
Exhaust Gas ◽  
Supply Pressure ◽  
Air Supply ◽  
Supply Systems

The air supply system plays a key role for Proton Exchange Membrane (PEM) fuel cells. The performance of PEM fuel cells can be significantly improved by increasing the air supply pressure and air stoichiometric ratio. However, the increased electrical power consumption of the conventional motor driven air compressor operated at higher pressure would reduce the overall efficiency of the PEM fuel cell system. This paper proposes three novel air supply systems in which the compressor is driven by the waste heat recovered by the Organic Rankine Cycle (ORC) from the stack cooling water and the exhaust gas. The influences of air supply pressure and air stoichiometric ratio on the PEM fuel cell performance and exhaust gas are investigated through the fuel cell stack model. The performance analysis of the air supply system is carried out using a thermodynamic simulation model. And the proposed three air systems are compared to an air system driven by the exhaust gas and the assisted motor. Results show that both the air pressure and air stoichiometric ratio are improved significantly. The gross output electric power and the net efficiency of the PEM fuel cells are also improved greatly because of higher operating pressure and the elimination of the compressor power consumption. Among the 3 proposed air systems, the air system which has a self-circulation to maintain the stack temperature has the best performance and is most stable in operation.

Initial Development of a Method for Optical Measurement of Water Droplet Formation in the Cathode Flow Channel of a PEM Fuel Cell

2013 ◽  
Author(s):  
Hannah Stuart ◽  
Kristopher Inman ◽  
Xia Wang
Keyword(s):  
Fuel Cell ◽  
Water Droplet ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Droplet Formation ◽  
Flow Channel ◽  
Operating Conditions ◽  
Ex Situ ◽  
Flow Channels ◽  
Water Formation

Cathode flooding in Proton Exchange Membrane (PEM) fuel cells, or the displacement of reactant gases from the catalyst layer by water formation, limits performance and durability. Water transport is not yet well understood and can vary under different operating conditions, such as temperature. Previous work performed to characterize water formation has mostly involved water visualization, using materials/construction which could alter water condensation characteristics. The objective of this work is to investigate a method to optically measure the relative size of water droplet formation in PEM fuel cell cathode gas flow channels using an unobtrusive and previously developed temperature sensor. A single-sensor mathematical model was developed which considers channel geometry, fiber diameter, and water droplet shape and size. Droplet formation involved three different possible shapes, resulting from different hydrophobic properties of channel material. Ex situ testing utilized chromium doped yttrium aluminum garnet as the chosen phosphor, applied to a carbon paper GDL. No correlation was found between the theoretical model and the experimental findings. Although signal attenuation cannot accurately predict droplet size, it is still possible to characterize water droplet formation using statistical analysis. Since a water droplet consistently produces measurable attenuation, the frequency of water droplet detection in the flow channel can be used to characterize the amount of water formation or flooding in the cathode flow channels. The work is ongoing and new methods of water droplet characterization are still being investigated.

Experiments Toward Fundamental Validation of PEM Fuel Cell Models

2005 ◽  
Author(s):  
Q. G. Yan ◽  
Q. Y. Liu ◽  
H. Toghiani ◽  
J. X. Wu
Keyword(s):  
Fuel Cell ◽  
Relative Humidity ◽  
Operating Conditions ◽  
Cell Performance ◽  
Experimental Results ◽  
Polarization Curves ◽  
Polymer Electrolyte Fuel Cell ◽  
Operating Pressure ◽  
Cell Models ◽  
Fuel Cell Performance

Detailed experimental parameters are controlled and measured under widely varying operating conditions. In addition to polarization curves, feed gas flow rates, temperatures, pressure drop, and relative humidity are all measured accurately. Performance of a polymer electrolyte fuel cell (PEFC) was studied using steady-state polarization curves and electrochemical impedance spectroscopy (EIS) techniques. The effects of relative humidity, temperature, pressure and feed gas stoichiometry on fuel cell performance were investigated. It was found that the humidity of both the anode and cathode inlet gases had a significant effect on fuel cell performance. The experimental results showed that a decrease in the cathode humidity has a more detrimental effect on cell performance than a comparable decrease in the anode humidity. The obtained results will be used to define conditions of optimal hydration of the membrane. Based on the performance and resistance measurements, optimal humidification can be achieved. The polarization curves of the cell at different operating temperatures showed that fuel cell performance was improved with increasing temperature from 65 to 75°C. The fuel cell performance also improved as the operating pressure was increased from 1 atm to 4 atm. The resistance of the working fuel cell showed that the membrane resistance increased as the feed gas relative humidity (RH) decreased. The experimental results were compared with the results of a CFD mathematical model. These experimental data will provide a baseline for validation of fuel cell models.

scholarly journals Experimental investigation on water-injected twin-screw compressor for fuel cell humidification

2012 ◽  
Vol 226 (12) ◽  
pp. 2925-2932 ◽  
Author(s):  
Talal Ous ◽  
Elvedin Mujic ◽  
Nikola Stosic
Keyword(s):  
Fuel Cell ◽  
Relative Humidity ◽  
Constant Pressure ◽  
Water Injection ◽  
Injection Rate ◽  
Fuel Cell Stack ◽  
Balance Of Plant ◽  
Air Supply ◽  
Twin Screw ◽  
Mass Flow Rates

Water injection in twin-screw compressors was examined in order to develop effective humidification and cooling schemes for fuel cell stacks as well as cooling for compressors. The temperature and the relative humidity of the air at suction and exhaust of the compressor were monitored under constant pressure and water injection rate and at variable compressor operating speeds. The experimental results showed that the relative humidity of the outlet air was increased by the water injection. The injection tends to have more effect on humidity at low operating speeds/mass flow rates. Further humidification can be achieved at higher speeds as a higher evaporation rate becomes available. It was also found that the rate of power produced by the fuel cell stack was higher than the rate used to run the compressor for the same amount of air supplied. The efficiency of the balance of plant was, therefore, higher when more air is delivered to the stack. However, this increase in the air supply needs additional subsystems for further humidification/cooling of the balance-of-plant system.

An Improved Model to Predict Flooding/Dehydration in PEM Fuel Cells

2005 ◽  
Author(s):  
S. Maharudrayya ◽  
S. Jayanti ◽  
A. P. Deshpande
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Water Vapour ◽  
Current Density ◽  
Pem Fuel Cells ◽  
Operating Conditions ◽  
Fickian Diffusion ◽  
Closed Form Expression ◽  
Water Vapour Diffusion ◽  
Improved Model

Maintaining proper water balance between the production of water due to reaction and its removal by evaporation is very important for the successful operation of a Polymer Electrolyte Membrane (PEM) fuel cell. Imbalance between the two processes can result in either flooding of the electrodes/ gas channels or the dehydration of the membrane. The water management issue is especially critical for ambient temperature operation of the fuel cell. Several experimental and theoretical studies relevant to water management have been carried out to investigate means of reducing the flooding of electrodes/channels or the dehydration of membrane. Bernardi [9] and Wang et al. [11] have developed theoretical models for the prediction of when flooding/dehydration may take place. In the present study, an improved model is developed which combines the advantages of these two models. The Bernardi [9] model is extended to include mass transfer resistances. Following Wang et al. [11], the Stefan-Maxwell description of multicomponent diffusion is replaced by Fickian diffusion. In addition, water vapour diffusion to both anode and cathode sides is included in the model. The overall model is in the form of a closed-form expression for the critical or threshold or balance current density at which the water production rate and the water vapour evacuation rate are exactly balanced. The model shows that the balance current density is a function of operating conditions, properties of electrode, flow and geometric parameters in the gas channels. It has been validated by comparing the predictions with the experimental data of Tu¨ber et al. [5] and Eckl et al. [8].

PEM Fuel Cell Research Direction for Automotive Application

2005 ◽  
Author(s):  
John Fagley ◽  
Jason Conley ◽  
David Masten
Keyword(s):  
Fuel Cell ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Department Of Energy ◽  
Limiting Current ◽  
Automotive Application ◽  
Commercial Application ◽  
Related Research

In recent years, there has been an increasing amount of PEM (proton exchange membrane) fuel cell-related research conducted and subsequently published by universities and public institutions. While a good deal of this research has been useful for understanding the underlying fundamental aspects of fuel cell components and operation, much of it is not as useful for a group working on automotive applications as it could be. The reason for this is that in order to be put to practical use in an automotive application, the system being studied must meet certain constraints; satisfying targets for projected system costs, system efficiency, volumetric and gravimetric power densities (packaging), and operating conditions. For example, numerous recent publications show studies with PEM fuel cells designed and built such that limiting current density is achieved at 0.9 A/cm2 or lower, and voltages of 600 mV can only be achieved at current densities less than 0.6 A/cm2. This type of performance is sufficiently below what is required for commercial application, that any conclusions drawn from these works are difficult to extrapolate to a system of commercial automotive interest. The purpose of this article is to show, through use of engineering calculations and cost projections, what operating conditions and performance are required in a commercial automotive fuel cell application. In addition, best known (public domain) performance and corresponding conditions are given, along with Department of Energy Freedom Car targets, which can be used for state-of-the-art benchmarking. Also, reference is made to a university publication where performance (500 mV at 1.5 A/cm2) close to automotive application targets was achieved, and important aspects of their components and flow field geometry are highlighted. It is our hope that through this publication, further PEM fuel-cell related research can be directed toward the region of greatest interest for commercial, automotive application.

scholarly journals Effects of hydrogen relative humidity on the performance of an air-breathing PEM fuel cell

2019 ◽  
Vol 30 (4) ◽  
pp. 2077-2097 ◽  
Author(s):  
Zhenxiao Chen ◽  
Derek Ingham ◽  
Mohammed Ismail ◽  
Lin Ma ◽  
Kevin J. Hughes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Relative Humidity ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Air Breathing ◽  
Content Type ◽  
The Heat Transfer Coefficient

Purpose The purpose of this paper is to investigate the effects of hydrogen humidity on the performance of air-breathing proton exchange membrane (PEM) fuel cells. Design/methodology/approach An efficient mathematical model for air-breathing PEM fuel cells has been built in MATLAB. The sensitivity of the fuel cell performance to the heat transfer coefficient is investigated first. The effect of hydrogen humidity is also studied. In addition, under different hydrogen humidities, the most appropriate thickness of the gas diffusion layer (GDL) is investigated. Findings The heat transfer coefficient dictates the performance limiting mode of the air-breathing PEM fuel cell, the modelled air-breathing fuel cell is limited by the dry-out of the membrane at high current densities. The performance of the fuel cell is mainly influenced by the hydrogen humidity. Besides, an optimal cathode GDL and relatively thinner anode GDL are favoured to achieve a good performance of the fuel cell. Practical implications The current study improves the understanding of the effect of the hydrogen humidity in air-breathing fuel cells and this new model can be used to investigate different component properties in real designs. Originality/value The hydrogen relative humidity and the GDL thickness can be controlled to improve the performance of air-breathing fuel cells.

scholarly journals Numerical Study on Humidification Performance of Fuel Cell Test Platform Humidifier

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3839 ◽  
Author(s):  
Tiancai Ma ◽  
Kai Wang ◽  
Qiongqiong Zhou ◽  
Weikang Lin ◽  
Ming Cong ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Water Temperature ◽  
Numerical Study ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Air Velocity ◽  
Humidity Control ◽  
Test Platform ◽  
Temperature And Humidity ◽  
Cell Test

Temperature and humidity are important parameters in the operation of proton exchange membrane fuel cell (PEMFC), which have an important impact on the performance of fuel cell. Fuel cell test platform is an important tool to study the performance of fuel cells, and its temperature and humidity control module is also the key in the research process of the test platform, so that it can provide the gas with precise temperature and humidity control during the test process of the fuel cell. In this paper, a humidifier combined with bubbling and spraying is adopted for the application of test platform, and the numerical simulation model of the humidifier is established. According to the model, the influence of operating conditions of humidifier on humidification performance is verified, such as inlet air velocity and the humidifying water temperature. The results indicate that the inlet air velocity and the humidifying water temperature have great influence on the humidifying performance of the humidifier. The humidifying performance decreases with the increase of the inlet air velocity and increases with the increase of the humidifying water temperature respectively. In addition, the humidification performance of the humidifier is verified.

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