2005 PEM fuel cell performance and its two-phase mass transport
PEM燃料电池阴极加湿对浓差极化的影响
PEM燃料电池阴极加湿对浓差极化的影响薛坤1肖金生1,2（1武汉理工大学材料复合新技术国家重点实验室，2汽车工程学院，湖北430070）摘要：运用FLUENT的PEM模块对质子交换膜燃料电池不同的加湿程度进行研究。
分析了不同的加湿程度对燃料电池性能的影响，尤其讨论了在高电流密度情况下，浓差极化对燃料电池性能的影响。
对80℃阴极气体分为100%加湿和50%加湿进行对比，结果表明,低电流密度100%加湿性能更好，在高电流密度时50%加湿性能更好。
另外分析了浓差极化区燃料电池内部液态水、氧气浓度、电流密度以及电极电势分布，表明浓差极化仅在燃料电池的部分区域发生。
采取有效的排水措施可以使100%饱和加湿获得更高的性能。
关键词：燃料电池电池性能阴极加湿浓差极化1引言质子交换膜燃料电池（PEMFC）作为一种新型的能源处理方式，具有工作温度低、无污染、无腐蚀、比功率大、启动迅速等优点, 已经成为能源领域研究的热点之一[1]。
在燃料电池内部，H+的迁移必须有液态水存在的情况下迁移，因此膜必须保持润湿，才能减小膜电阻。
上海交通大学的马捷等[2]对质子交换膜燃料电池膜内水迁移特性做了研究和同时对水管理和加湿方法做了探讨。
Chen J, Matsuura T, Hori M [3]等研究了一种在扩散层和催化层之间增加了水管理层（WML）的新型气体扩散层结构。
并对优化的气体扩散层进行模拟，预测了电极中水的分布图。
Choi K H, Park D J, Rho Y W[4]等对质子交换膜燃料电池膜内水迁移特性做了研究和同时对水管理和加湿方法做了探讨。
有效的水管理可以通过膜电极和电池结构的优化设计来实现，当不足以获得足够的含水率时，只能采用加湿技术。
质子交换膜燃料电池阴极增湿对于燃料电池性能的影响比较复杂。
阴极反应生成水，如果不能及时排出去，容易导致阴极水淹，影响氧气扩散，甚至导致反极。
本文通过建立一个双流道模型，对阳极饱和加湿，研究阴极不同的加湿程度对于燃料电池性能的影响，重点分析在大电流密度情况下，阴极加湿对于浓差极化的影响。
车用大功率燃料电池低温冷启动分析
^jm 11】汽车工程师Automotive EngineerFOCUS 技术聚焦Automotiiv E ngineer^摘要：质子交换膜燃料电池低温冷启动被认为是影响燃料电池汽车商业化的主要因素之一。
文章根据某款燃料电池车型开发目标需求，对匹配的120 kW 大功率燃料电池在-30。
"低温启动热平衡初步分析，基于电堆外加热控制策略，经初步 匹配计算，在理想情况下需要13 min 才能启动，为拟开发目标设定提供了依据。
文章对开发大功率燃料电池乘用车具有 参考意义。
关键词:大功率燃料电池；低温冷启动；计算分析Analysis of Cold Starting Performance of High Power PEMFC used for VehicleAbstract ： Low temperature cold start of PEMFC is considered to be one of the main factors affecting the commercialization offuel cell vehicle. In this paper,according to the development target demand of a fuel cell vehicle, the preliminary analysis of the heat balance of the matched 120kw high-power fuel cell at 一30°C is conducted. Based on the heating control strategy outsidethe stack, the preliminary matching calculation shows that it takes 13 minutes to start under ideal conditions, which provides the basis for the target setting of the proposed development. This paper has reference significance for the development of high-power fuel cell passenger vehicle.Key words : High power PEMFC; Start-up at low temperature; Analysis质子交换膜燃料电池(PEMFC )相比传统内燃机, 拥有其特有优势h ,PEMFC 的高效率、高比功率、零排 放及响应快速等特性使其成为未来汽车领域最有潜力的动力源45;、车用PEMFC 在商业化进程中，冷启动困 难或启动时间过长是主要制约因素之一6目前，国内 外车型对燃料电池发动机冷启动能力进行了大量实验,国外相关车型已量产且技术相对成熟3w,国内大多从实际运行情况来看，在低温启动方面的技术称不上很好，如表1所示。
Fluent6.2燃料电池帮助手册
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Technical Support
If you encounter difficulties while using FLUENT, please first refer to the section(s) of the manual containing information on the commands you are trying to use or the type of problem you are trying to solve. The product documentation is available from the online help on the documentation CD, or from the Fluent Inc. User Services Center (). If you encounter an error, please write down the exact error message that appeared and note as much information as you can about what you were doing in FLUENT. Then refer to the following resources available on the Fluent Inc. User Services Center (): • Installation and System FAQs - link available from the main page on the User Services Center. The FAQs can be searched by word or phrase, and are available for general installation questions as well as for products. • Known defects for FLUENT - link available from the product page. The defects can be searched by word or phrase, and are listed by categories. • Online Technical Support - link available from the main page on the User Services Center. From the Online Technical Support Portal page, there is a link to the Search Solutions & Request Support page, where the solutions can be searched by word or phrase. The User Services Center also provides online forums, where you can discuss topics of mutual interest and share ideas and information with other Fluent users, and the ability to sign up for e-mail notifications on our latest product releases.
能源专业外文翻译--燃料电池及其发展前景1
外文原文：Fuel Cells and Their ProspectsA fuel cell is an electrochemical conversion device. It produces electricity fromfuel (on the anode side) and an oxidant (on the cathode side), which react in the presence of an electrolyte. The reactants flow into the cell, and the reaction products flow out of it, while the electrolyte remains within it. Fuel cells can operate virtually continuously as long as the necessary flows are maintained.Fuel cells are different from electrochemical cell batteries in that they consume reactant from an external source, which must be replenished--a thermodynamically open system. By contrast batteries store electrical energy chemically and hence represent a thermodynamically closed system.Many combinations of fuel and oxidant are possible. A hydrogen cell uses hydrogen as fuel and oxygen (usually from air) as oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include chlorine and chlorine dioxide.Fuel cell designA fuel cell works by catalysis, separating the component electrons and protonsof the reactant fuel, and forcing the electrons to travel though a circuit, hence converting them to electrical power. The catalyst typically comprises a platinum group metal or alloy. Another catalytic process takes the electrons back in, combining them with the protons and oxidant to form waste products (typically simple compounds like water and carbon dioxide).A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load.Voltage decreases as current increases, due to several factors:•Activation loss•Ohmic loss (voltage drop due to resistance of the cell components and interconnects)•Mass transport loss (depletion of reactants at catalyst sites under high loads, causing rapid loss of voltage)To deliver the desired amount of energy, the fuel cells can be combined in series and parallel circuits, where series yield higher voltage, and parallel allows a stronger current to be drawn. Such a design is called a fuel cell stack. Further, the cell surface area can be increased, to allow stronger current from each cell.Proton exchange fuel cellsIn the archetypal hydrogen–oxygen proton exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane, (the electrolyte), separates the anode and cathode sides. This was called a "solid polymer electrolyte fuel cell" (SPEFC) in the early 1970s, before the proton exchange mechanism was well-understood. (Notice that "polymer electrolyte membrane" and "proton exchange mechanism" result in the same acronym.)On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants causing them to become what is commonly referred to as multi-facilitated proton membranes (MFPM). The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water — in this example, the only waste product, either liquid or vapor.In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel, methanol (see: direct-methanol fuel cells and indirect methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water.The materials used in fuel cells differ by type. In a typical membrane electrode assembly (MEA), the electrode–bipolar plates are usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum, nano iron powders or palladium) for higher efficiency. Carbon paper separates them from the electrolyte. The electrolyte could be ceramic or a membrane.Oxygen ion exchange fuel cellsIn a solid oxide fuel cell design, the anode and cathode are separated by an electrolyte that is conductive to oxygen ions but non-conductive to electrons. The electrolyte is typically made from zirconia doped with yttria.On the cathode side, oxygen catalytically reacts with a supply of electrons to become oxygen ions, which diffuse through the electrolyte to the anode side. On the anode side, the oxygen ions react with hydrogen to form water and free electrons. A load connected externally between the anode and cathode completes the electrical circuit.Fuel cell design issuesCostsIn 2002, typical cells had a catalyst content of US$1000 per-kilowatt of electric power output. In 2008 UTC Power has 400kw Fuel cells for $1,000,000 per 400kW installed costs. The goal is to reduce the cost in order to compete with current market technologies including gasoline internal combustion engines. Many companies are working on techniques to reduce cost in a variety of ways including reducing the amount of platinum needed in each individual cell. Ballard Power Systems have experiments with a catalyst enhanced with carbon silk which allows a 30% reduction (1 mg/cm2 to 0.7 mg/cm2) in platinum usage without reduction in performance.The production costs of the PEM (proton exchange membrane). The Nafion membrane currently costs €400/m². In 2005 Ballard Power Systems announced that its fuel cells will use Solupor, a porous polyethylene film patented by DSM.Water and air management (in PEMFC). In this type of fuel cell, the membrane must be hydrated, requiring water to be evaporated at precisely the same rate that it is produced. If water is evaporated too quickly, the membrane dries, resistance across it increases, and eventually it will crack, creating a gas "short circuit" where hydrogen and oxygen combine directly, generating heat that will damage the fuel cell. If the water is evaporated too slowly, the electrodes will flood, preventing the reactants from reaching the catalyst and stopping the reaction. Methods to manage water in cells are being developed like electroosmotic pumps focusing on flow control. Just as in a combustion engine, a steady ratio between the reactant and oxygen is necessary to keep the fuel cell operating efficiently.Temperature managementThe same temperature must be maintained throughout the cell in order to prevent destruction of the cell through thermal loading. This is particularly challenging as the 2H2 + O2 =2H2O reaction is highly exothermic, so a large quantity of heat is generated within the fuel cell.Durability, service life, and special requirements for some type of cells Stationary fuel cell applications typically require more than 40,000 hours of reliable operation at a temperature of -35°C to40°C, while automotive fuel cells require a 5,000 hour lifespan (the equivalent of 150,000 miles) under extreme temperatures. Automotive engines must also be able to start reliably at -30 °C and have a high power to volume ratio (typically 2.5 kW per liter).HistoryThe principle of the fuel cell was discovered by German scientist Christian Friedrich Schönbein in 1838 and published in one of the scientific magazines of thetime. Based on this work, the first fuel cell was demonstrated by Welsh scientist Sir William Robert Grove in the February 1839 edition of the Philosophical Magazine and Journal of Science, and later sketched, in 1842, in the same journal. The fuel cell he made used similar materials to today's phosphoric-acid fuel cell.In 1955, W. Thomas Grubb, a chemist working for the General Electric Company (GE), further modified the original fuel cell design by using a sulphonated polystyrene ion-exchange membrane as the electrolyte. Three years later another GE chemist, Leonard Niedrach, devised a way of depositing platinum onto the membrane, which served as catalyst for the necessary hydrogen oxidation and oxygen reduction reactions. This became known as the“Grubb-Niedrach fuel cell”. GE went on to develop this technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini. This was the first commercial use of a fuel cell. It wasn't until 1959 that British engineer Francis Thomas Bacon successfully developed a 5 kW stationary fuel cell. In 1959, a team led by Harry Ihrig built a 15 kW fuel cell tractor for Allis-Chalmers which was demonstrated across the US at state fairs. This system used potassium hydroxide as the electrolyte and compressed hydrogen and oxygen as the reactants. Later in 1959, Bacon and his colleagues demonstrated a practical five-kilowatt unit capable of powering a welding machine. In the 1960s, Pratt and Whitney licensed Bacon's U.S. patents for use in the U.S. space program to supply electricity and drinking water (hydrogen and oxygen being readily available from the spacecraft tanks).United Technologies Corporation's UTC Power subsidiary was the first company to manufacture and commercialize a large, stationary fuel cell system for use as a co-generation power plant in hospitals, universities and large office buildings. UTC Power continues to market this fuel cell as the PureCell 200, a 200 kW system (although soon to be replaced by a 400 kW version, expected for sale in late 2009). UTC Power continues to be the sole supplier of fuel cells to NASA for use in space vehicles, having supplied the Apollo missions, and currently the Space Shuttle program, and is developing fuel cells for automobiles, buses, and cell phone towers; the company has demonstrated the first fuel cell capable of starting under freezing conditions with its proton exchange membrane automotive fuel cell.Fuel cell efficiencyThe efficiency of a fuel cell is dependent on the amount of power drawn from it. Drawing more power means drawing more current, which increases the losses in the fuel cell. As a general rule, the more power (current) drawn, the lower the efficiency.Most losses manifest themselves as a voltage drop in the cell, so the efficiency of a cell is almost proportional to its voltage. For this reason, it is common to show graphs of voltage versus current (so-called polarization curves) for fuel cells. A typical cell running at 0.7 V has an efficiency of about 50%, meaning that 50% of the energy content of the hydrogen is converted into electrical energy; the remaining 50% will be converted into heat. (Depending on the fuel cell system design, some fuel might leave the system unreacted, constituting an additional loss.)For a hydrogen cell operating at standard conditions with no reactant leaks, the efficiency is equal to the cell voltage divided by 1.48 V, based on the enthalpy, or heating value, of the reaction. For the same cell, the second law efficiency is equal to cell voltage divided by 1.23 V. (This voltage varies with fuel used, and quality and temperature of the cell.) The difference between these numbers represents the difference between the reaction's enthalpy and Gibbs free energy. This difference always appears as heat, along with any losses in electrical conversion efficiency.Fuel cells do not operate on a thermal cycle. As such, they are not constrained, as combustion engines are, in the same way by thermodynamic limits, such as Carnot cycle efficiency. At times this is misrepresented by saying that fuel cells are exempt from the laws of thermodynamics, because most people think of thermodynamics in terms of combustion processes (enthalpy of formation). The laws of thermodynamics also hold for chemical processes (Gibbs free energy) like fuel cells, but the maximum theoretical efficiency is higher (83% efficient at 298K) than the Otto cycle thermal efficiency (60% for compression ratio of 10 and specific heat ratio of 1.4). Comparing limits imposed by thermodynamics is not a good predictor of practically achievable efficiencies. Also, if propulsion is the goal, electrical output of the fuel cell has to still be converted into mechanical power with the corresponding inefficiency. In reference to the exemption claim, the correct claim is that the "limitations imposed by the second law of thermodynamics on the operation of fuel cells are much less severe than the limitations imposed on conventional energy conversion systems". Consequently, they can have very high efficiencies in converting chemical energy to electrical energy, especially when they are operated at low power density, and using pure hydrogen and oxygen as reactants.In practice, for a fuel cell operating on air (rather than bottled oxygen), losses due to the air supply system must also be taken into account. This refers to the pressurization of the air and dehumidifying it. This reduces the efficiency significantlyand brings it near to that of a compression ignition engine. Furthermore fuel cell efficiency decreases as load increases.The tank-to-wheel efficiency of a fuel cell vehicle is about 45% at low loads and shows average values of about 36% when a driving cycle like the NEDC (New European Driving Cycle) is used as test procedure. The comparable NEDC value for a Diesel vehicle is 22%. In 2008 Honda released a car with fuel stack claiming a 60% tank-to-wheel efficiency.Fuel cells cannot store energy like a battery, but in some applications, such as stand-alone power plants based on discontinuous sources such as solar or wind power, they are combined with electrolyzers and storage systems to form an energy storage system. The overall efficiency (electricity to hydrogen and back to electricity) of such plants (known as round-trip efficiency) is between 30 and 50%, depending on conditions. While a much cheaper lead-acid battery might return about 90%, the electrolyzer/fuel cell system can store indefinite quantities of hydrogen, and is therefore better suited for long-term storage.中文译文：燃料电池及其发展前景燃料电池是一种电化学转换装置。
我的FLUENT里面怎么没有ADDON选项呢
帮助| 搜索| 注册| 登陆| 排行榜| 发帖统计»傲雪论坛»『Fluent专版』打印话题寄给朋友作者我的FLUENT里面怎么没有ADDON选项呢. [精华]ggbaby版主发帖: 843 积分: 11 雪币: 286于2005-06-24 11:38实在是用的同一个东西.别人的有,在DEFINE->MODELS->ADDON. 我的就是没有....chenstar盼望2008发帖: 3128积分: 2雪币: 949来自:温暖的雪地于2005-06-24 12:05搞不清楚，按说addon都必须有特别的license。
Nittaku ANV WL-ST + DHS Hurricane III + Palio CJ8000------------------------------------------------------------------------------------------------- 茶壶深爱着茶叶，表达爱意时却遭到拒绝，茶壶大吼：为什么？这一切都是为什么？茶叶胆怯地说：俺妈说了，成天灌水的都不是好人。
ddydai发帖: 306积分: 1雪币: 72于2005-06-24 13:54是这些吗：/define/models/acoustics//define/models> addFLUENT Addon Modules:1. MHD Model2. Fiber Model3. PEM Fuel Cell Model4. SOFC Fuel Cell ModelEnter Module Number: [1] 4Fast-loading "C:\Fluent.Inc\addons\sofc1.1\lib\addon.bin" Done.Opening library "C:\Fluent.Inc\addons\sofc1.1"...Library "C:\Fluent.Inc\addons\sofc1.1\ntx86\2d\libudf.dll" opened sourceadjust_functiondiffusivityE_ConductivityWARNING!C:\Fluent.Inc\addons\sofc1.1tx86\2d\libudf.dll contains UDFUtilityFunctions.Only one set of UDFUtilityFunctions is supported.This is already in use by mhd2.0.The following UDFUtilityFunctions functions will be ignored:fl_uds_solid_solve_pfl_uds_compute_coeffsfl_uds_post_solve_updateDone.Addon Module: sofc1.1...loaded!ddydai发帖: 306 积分: 1 雪币: 72于2005-06-24 13:57来个图：有啊：此主题相关图片如下：pvxd发帖: 52积分: 1雪币: 51于2005-06-24 18:32楼上的有license吗？addon调进去以后能算吗？feizao发帖: 29 积分: 0 雪币: 29于2005-06-24 21:42晕，俺的也没有yuhuiphd海纳百川有容乃大发帖: 339积分: 1雪币: 147于2005-06-25 00:06用console命令就可以了。
Fuel cell and fuel cell
专利名称：Fuel cell and fuel cell 发明人：西原 雅人,松上 和人申请号：JP2003405710申请日：20031204公开号：JP4412985B2公开日：20100210专利内容由知识产权出版社提供摘要：PROBLEM TO BE SOLVED: To provide a fuel battery cell and a fuel battery in which power generating performance can be exerted sufficiently.SOLUTION: This is the fuel battery cell 30 in which on one side main face of a conductive support substrate 13, a fuel side electrode 7, a solid electrolyte 9, and an oxygen side electrode 11 are sequentially installed, in which an interconnector 12 is installed at the other side, and which has a fuel gas passage 15 in the interior. When the length of the gas passage forming direction of one side main face of the conductive support substrate 13 is made to be a (mm), the width of the direction perpendicular to it is made to be b (mm), the value of a×b satisfies 3,000 to 5,250.COPYRIGHT: (C)2005,JPO&NCIPI申请人：京セラ株式会社地址：京都府京都市伏見区竹田鳥羽殿町６番地国籍：JP更多信息请下载全文后查看。
质子交换膜燃料电池论文
资料范本本资料为word版本，可以直接编辑和打印，感谢您的下载质子交换膜燃料电池论文地点：__________________时间：__________________说明：本资料适用于约定双方经过谈判，协商而共同承认，共同遵守的责任与义务，仅供参考，文档可直接下载或修改，不需要的部分可直接删除，使用时请详细阅读内容质子交换膜燃料电池摘要能源和环境是全人类面临的重要课题，考虑可持续发展的要求，在电池领域质子交换膜燃料电池（PEMFC）技术正引起能源工作者的极大关注。
本论文简单介绍了一下质子交换膜燃料电池的组成、特点及其工作原理。
详细的从质子交换膜燃料电池的质子交换膜的材料、电催化剂的种类、双极板材料及其贮氢技术的困难方面论述了质子交换膜燃料电池的关键技术；同时从质子交换膜燃料电池的研发现状及其在电动车动力源、家庭电源、分散站和军事领域的应用做以介绍。
关键词：质子交换膜燃料电池；质子交换膜；双极板；电催化剂ABSTRACTEnergy and environment is the mankind faces an important subject，considering the requirements of sustainable development，the Proton Exchange Membrane Fuel Cell（PEMFC）technology is attracting the attention of energy workers. In this thesis，the introduction of proton exchange membrane fuel cell composition，working principle，domestic and international situation and its application prospects. In this thesis，a brief proton exchange membrane fuel cell composition，characteristics，and how it works and its Problems and prospects in the industrial development are outlined. Detail from the proton exchange membrane fuel cell proton exchange membrane materials，the type of electro-catalyst，the bipolar plate materials and the difficulties of hydrogen storage technologies discussed proton exchange membrane fuel cell，the key technologies； At the same time，from the proton exchange membrane fuel cell R & D Status and its power source in electric vehicles，household power，decentralized stations and military fields，the application to introduce.Key Words：Proton exchange membrane fuel cell;Proton exchange membrane; Bipolarplate; Electro catalyst引言能源是人类赖以生存发展的重要物质基础，也是国民经济发展的重要命脉，因而对人类及人类社会发展具有十分重要的意义。
具有烷基磺酸侧链的凝胶型聚苯并咪唑质子交换膜的制备与表征
化工进展Chemical Industry and Engineering Progress2024 年第 43 卷第 4 期具有烷基磺酸侧链的凝胶型聚苯并咪唑质子交换膜的制备与表征朱泰忠1，张良1，黄泽权1，罗伶萍1，黄菲1，薛立新1，2（1 浙江工业大学化工学院膜分离与水科学技术中心，浙江 杭州 310014；2温州大学化学与材料工程学院，浙江 温州 325035）摘要：磷酸（PA ）掺杂聚苯并咪唑（PBI ）以其优异的热化学稳定性和高玻璃化转变温度成为高温质子交换膜燃料电池（HT-PEMFCs ）的首选材料。
然而，由于低温下磷酸较弱的解离度和传递速率，导致膜的质子传导性能不佳，电池冷启动困难。
因此，研发可在宽温湿度范围内高效运行的高温质子交换膜成为当前挑战。
特别是拓宽其低温运行窗口、实现冷启动对这类质子交换膜燃料电池在新能源汽车领域的实际应用具有重要意义。
本文通过多聚磷酸溶胶凝胶工艺与内酯开环反应设计并合成了一系列磷酸掺杂的具有柔性烷基磺酸侧链的凝胶型聚苯并咪唑质子交换膜。
重点探究了烷基磺酸的引入以及侧链长度对磷酸掺杂水平、不同温湿度下的质子传导率及稳定性的影响规律。
研究结果表明，所制备的质子交换膜具有凝胶型自组装片层堆叠的多孔结构，有利于吸收大量磷酸并提供质子快速传输通道。
其中，PA/PS-PBI 展现出了在宽温域范围内均优于目前所报道的其他工作的质子传导性能。
特别是常温下，其质子传导率从原膜的0.0286S/cm 提升至0.0694S/cm 。
80℃下，其质子传导率从原膜的0.1117S/cm 提升至0.1619S/cm 。
200℃下，其质子传导率从原膜的0.2609S/cm 提升至0.3578S/cm 。
此外，该膜在80℃和0%相对湿度（RH ）条件下仍可具有与Nafion 膜在100%RH 时相当的质子传导率，为打破质子交换膜经典定义、实现宽温域（25~240℃）运行提供新的方案。
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l m r s sat v w ␣
liquid phase membrane or mixture relative solid saturation vapor water species
Greek symbols α net water transport coefficient αa anodic transfer coefficient αc cathodic transfer coefficient γ multiphase correction factor δ width (mm) ε porosity η overpotential (V) λ water content in membrane or individual mobility µ viscosity (N s cm−2 ) ν kinematic viscosity (cm2 s−1 ) ρ density (kg m−3 ) σ interfacial tension (N cm−1 ) Subscripts and superscripts a anode or air act activity c cathode or capillary d electro-osmotic drag diff diffusion eff effective g gas phase hyd hydraulic in inlet k phase k
Nomenclature a C D E Em fe F i0 I J(s) kr K L M N p R s Sh T u u v x catalyst surface area per unit volume (cm2 cm−3 ) species mass fraction diffusion coefficient (cm2 s−1 ) potential (V) Equivalent weight of ionomer (g (equiv.)−1 ) surface area of liquid water per unit volume Faraday constant (96487 C mol−2 ) exchange current density (A cm−2 ) current density (A cm−2 ) capillary pressure function relative permeability absolute permeability (cm2 ) characteristic size (cm) molecular weight (kg mol−1 ) mole flux (kg cm−2 s−1 ) pressure (Pa) universal gas constant (8.314 J mol−1 K−1 ) phase saturation Sherwood number temperature velocity vector (cm s−1 ) the x direction velocity component (cm s−1 ) the y direction velocity component (cm s−1 ) mole fraction
Keywords: Proton exchange membrane (PEM); Fuel cells; Two-phase flow; Water management
1. Introduction It is well known that water management is a critical issue in proton exchange membrane (PEM) fuel cell design and operations. On one hand, the polymer membrane in PEM fuel cells needs to be hydrated to maintain high proton conductivity. On the other hand, excessive liquid water may occupy a significant fraction of the pore volume in the catalyst layer and gas diffusion layer (GDL), thus may significantly reduce reactant transfer rate to the reaction sites and cause flooding. Therefore, proper water balance and management is essential to maintaining high performance of a PEM fuel cell. A good understanding and proper modeling of the various transport processes, especially water transport is essential for the improvement and optimization of a fuel cell and fuel cell sys∗
Abstract A two-phase flow model for a proton exchange membrane (PEM) fuel cell is developed. The model is based on the mixture flow model and the unified approach is used. Instead of using a separate model for the catalyst layer, the catalyst layers are now included in the respective unified domains for the cathode and anode, thus continuity boundary conditions at the interface between the catalyst layer (CL) and the gas diffuser layer (GDL) are no longer needed. The model couples the flows, species, electrical potential, and current density distributions in the cathode and anode fluid channels, gas diffusers, catalyst layers and membrane respectively. Furthermore, the two-phase flow model is also used in the anode side, and the momentum transfer between the liquid and gas phases due to phase change is taken into consideration. Experiments have been conducted to study the performances of a PEM fuel cell and the results are used to improve and validate our model. The modeling results of polarization curves compared well with the experimental data. The model is used to study the influences of fuel cell operating temperature, operating pressure and humidification temperature on the oxygen, vapor and liquid water transports, as well as fuel cell performances. © 2004 Elsevier B.V. All rights reserved.
Corresponding author. Tel.: +1 305 284 2019; fax: +1 305 284 2019. E-mail address: hliu@ (H. Liu).
tems. At present many of the transport phenomena inside a fuel cell cannot be directly observed or measured; thus making mathematical modeling a critical tool to understanding these transport phenomena. Some of the pioneering work in PEM fuel cell modeling includes those by Bernardi and Verbrugge [1,2], Hill and Verbrugge [3], Springer et al. [4,5]. These one-dimensional models laid the foundation for PEM fuel cell modeling. Pseudo two-dimensional model includes those by Fuller and Newman [6] and Nguyen and White [7], which included the effects of reactant consumption along the flow channels. Gurau et al. [8] developed a two-dimensional PEM fuel cell model that coupled fluid flow, mass transfer and the electrokinetics, thus introducing the computational fluid dynamics (CFD) into fuel cell modeling. The approach adopted was a unified approach that eliminated the need of prescribing artificial boundary conditions at the various interfaces between the different components of a fuel cell. Zhou and Liu [9]