A numerical analysis of an air-cooled proton exchange membrane fuel cell (PEMFC) has been conducted. The model utilizes the Eulerian multi-phase approach to predict the occurrence and transport of liquid water inside the cell. It is assumed that all the waste heat must be carried out of the fuel cell with the excess air which leads to a strong temperature increase of the air stream. The results suggest that the performance of these fuel cells is limited by membrane overheating which is ultimately caused by the limited heat transfer to the laminar air stream. A proposed remedy is the placement of a turbulence grid before such a fuel cell stack to enhance the heat transfer and increase the fuel cell performance.

A numerical analysis of a proton exchange membrane fuel cell (PEMFC) that contains a perforated metal plate at the cathode side has been conducted. The model utilizes the Eulerian multi-phase approach to predict the occurrence and transport of liquid water inside the cell. The PEMFC that was modelled contained micro-channels at both anode and cathode side. Results suggest that despite the fact that the inlet gases are fully saturated (RH = 100%), the holes in the metal sheet remain in the single phase, and the predicted maximum current densities are accordingly high. The high thermal conductivity of the metal sheets result in only a moderate temperature increase in the cell, and the fuel cell membrane is predicted to be hydrated under all conditions investigated. The fact that the cathode channel and the holes in the metal sheet remain dry is attributed to the high pressure drop inside the flow channel.

In this study 3-D CFD modeling of a cylindrical stack Proton-exchange membrane fuel cell (PEMFC) is provided. The H2O-O2 PEMFC uses a 10.8 mm 2 area membrane and Platinum (Pt) catalyst. The paper presents the methodology for the PEMFC commercial software module, the set-up of the Computational Fluid Dynamics (CFD) geometry, mesh and boundary conditions. Results for the current-voltage performance curves and 3-D contour plots of the fluid, heat and species concentrations within the PEMFC are given. Results are presented for a low-temperature fuel cell using NAFION membrane and a high-temperature fuel cell using BZY membrane.

Electrochemical energy conversion and storage devices are becoming a large part of the renewable energy market. For these systems to operate optimally over a wide range of operating and environmental conditions, advanced strategies for thermal management must be developed. Incorporating microencapsulated phase change materials (MEPCM), which utilize latent heat storage, into coolant fluids has been shown to increase the fluid’s thermal capacity. This mitigates the temperature gradient between the coolant loop inlet and outlet which is important in systems such as fuel cells and batteries where sensitivity to temperature directly impacts the electrochemical reaction, transport processes, and component lifetimes. The use of MEPCMs may allow for lower coolant flow rates which may reduce parasitic pumping power, further increasing overall system efficiency. In this work MEPCM material is added to liquid water at several mass concentration ratios, and an analytical study was conducted to determine pressure drop and channel power requirements. The viscosity of the slurry is measured along with its density, conductivity, and heat capacity as a function of temperature. Inlet and outlet channel slurry temperatures are monitored, flow rate is controlled, and the heat flux can be varied to simulate waste heat outputs of various devices. From this data the optimal conditions for the slurry flow can be assessed and thermal management strategies can be designed for specific devices.

A metal foam filled microchannel cooling device for polymer-electrolyte-membrane fuel cell (PEFC) and flow batteries was investigated experimentally and numerically in this study. Nickel foam was selected due to its high conductivity, large surface area, low density and low cost. The properties of the nickel foam were determined analytically and experimentally. Experiments were conducted to obtain pressure drop at various Reynolds numbers for metal foams of varying porosities. The experimental data was used to provide inputs for the numerical model. A modeling approach for flow in a metal foam filled channel was validated with the available data. The validated model was then used to analyze the heat transfer and fluid flow characteristics of the metal foam microchannel. Two different locations of the cooling device with respect to the PEF C stack were investigated. The thermal resistance and pressure drop change with Reynolds number are presented. Significant temperature drop was observed with the metal foam microchannel design. The modeling results can be used to guide the direction of future experiments.

Numerical models for the evaluation of cryo-adsorbent based hydrogen (H 2 ) storage systems for fuel cell vehicles were developed and validated against experimental data. These models simultaneously solve the equations for the adsorbent thermodynamics together with the conservation equations for heat, mass, and momentum. The models also use real gas thermodynamic properties for hydrogen. Model predictions were compared to data for charging and discharging both activated carbon and MOF-5™ systems. Applications of the model include detailed finite element analysis simulations and full vehicle-level system analyses. The full system models were used to compare prospective system design performance given specific options, such as the adsorbent materials, pressure vessel types, internal heat exchangers, and operating conditions. The full vehicle model, which also allows the user to compare adsorbent systems with compressed gas, metal hydride, and chemical hydrogen storage systems, is based on an 80 kW fuel cell with a 20 kW battery evaluated using standard drive cycles. This work is part of the Hydrogen Storage Engineering Center of Excellence (HSECoE), which brings materials development and hydrogen storage technology efforts together to address onboard hydrogen storage in light duty vehicle applications. The HSECoE spans the design space of the vehicle requirements, balance of plant requirements, storage system components, and materials engineering. Theoretical, computational, and experimental efforts are combined to evaluate, design, analyze, and scale potential hydrogen storage systems and their supporting components against the Department of Energy (DOE) 2020 and Ultimate Technical Targets for Hydrogen Storage Systems for Light Duty Vehicles.

The proton exchange membrane fuel cell (PEMFC) system is becoming one of the most potential power systems for automotive applications in the future. Though the efficiency of PEMFC is high, almost half of the hydrogen energy is taken away by coolant without being utilized. Organic Rankine Cycle (ORC) could be used for the waste heat recovery of PEMFC. The working fluid of ORC flows directly into the fuel cell stack and cool the stack as the same time. In this paper, the feasibility of R245ca as the coolant of PEMFC and working fluid of ORC is studied. A simulation model of the fluid flow and heat transfer of R245ca in PEMFC cooling plates is set up with the CFD software package FLUENT. The Volume of Fluid (VOF) model is used to simulate the two-phase flow. Results show that R245ca can efficiently remove the waste heat and ensure uniform temperature distribution in PEMFC.

In this study, two novel valve-less impedance pumps are applied, for the first time, in the liquid fuel supply of a Direct Sodium Borohydride–Hydrogen Peroxide Fuel Cell (DBHPFC). This valve-less pump prevents the pump corrosion and serves appropriately to reduce the volume and weight of fuel cell systems. It comprises an amber latex rubber tube, connected at both ends to rigid stainless steel tubes of different acoustic impedance, and a simple actuation mechanism which combines a small DC motor and a cam. The motor activated cam periodically compresses the elastic tube at a position asymmetric from the tube ends. Traveling waves, emitted from the compression, combine with reflected waves at the impedance-mismatched rubber tube/stainless tube interfaces. The resulting wave interference creates a pressure gradient and generates a net flow. A DBHPFC with the active area of 25 cm 2 is constructed. It is shown that the maximum pumping rate can achieve 30 ml/min with the DBHPFC connected. The corresponding maximum power and current are 13.0 W and 25.5 A, respectively. Specific power, volumetric power density, and back work ratio of the DBHPFC using this pumping method are shown superior to those of the other pumping configuration with the peristaltic pumps.

Proton exchange membrane fuel cells directly convert into electricity the chemical energy of hydrogen and oxygen from air. The by-products are just water and waste heat. Depending on the operating conditions the water may be in the liquid or gas phase, and liquid water can hence plug the porous media in the fuel cell, and, more importantly, the flow channels and outlet ports of a single cell in a stack. These problems may be avoided if the fuel cell operates in a way that both the anode and cathode outlet stream are exactly fully humidified, i.e. the relative humidity is at 100 %. Such operation can conceivably be obtained by adjusting the operating conditions using dew point diagrams. In this paper numerical results will be presented of two different flow field arrangements, both using the interdigitated flow field. It will be shown that arranging the gas streams in a counter-flow, “ x -flow” modus is the preferred option. Moreover, a detailed analysis of the preferred channel width and land area shows that the finest pitch is predicted to yield the highest membrane hydration levels and is thus preferred.

A centrifugal compressor for fuel-cell vehicles, which makes compressed air and sends it to the fuel-cell stack, is investigated in this paper. It is the only part of revolution in the system, and it consumes most of the system power. Therefore, it is important to achieve low noise level as well as high efficiency. The operating line of this compressor is determined along the highest efficiency points and during the design-point operation the blade tone noise is the main contributor. It is widely known that the blade passing frequency (BPF) noise components is due to the circumferential flow fluctuations of the impeller. So the noise spectrum of this compressor needs to be examined closely. So, an experimental study is designed to investigate the aero-acoustic characteristics of a centrifugal compressor in detail. The existing system is modified to allow pressure measurements at the inlet and outlet of the impeller. Four microphone probes are also installed to determine the noise level in an isolated room. Tests are carried out to investigate the phenomena governing the tonal noise and the dominant noise source of the centrifugal compressor. With such information on noise, a design optimization process is carried out to determine a superior design point which will guarantee good performance and low noise level at the design point. The optimization is performed using the surrogate management framework with the simulated results obtained at sampled points. The final optimal design point and the comparison between the optimal designed compressor and the existing centrifugal compressor are described in the last section of this paper.

In present Polymer Electrolyte Fuel Cell (PEFC), the cathode oxygen reduction reaction (ORR) is dominant at high current density condition. In order to accelerate this reaction, oxygen, proton and electron, which move in void space, ionomer and carbon black (CB) or CNT respectively, have to be transferred at Pt surface smoothly. Accordingly, it is very important to know the transport phenomena in catalyst layer (CL) to design the optimum structure and to develop new materials. In order to investigate the transport phenomena in CL by applying calculation technique, in this study, heterogeneous CB aggregate structure was simulated by computer calculation as the first examination. In addition, ionomer coating condition and proton conductivity were examined. Furthermore oxygen, proton and electron transfer in 3D porous catalyst layer were calculated, and the effective reaction field was examined in various structure and ionomer condition.

In automotive Polymer Electrolyte Fuel Cell (PEFC) system, dry gas purge operation is needed at shutdown condition in order to remove the liquid water in gas diffusion layer (GDL) and to reduce the oxygen diffusion inhibition by liquid water in GDL. However, exceed drying operation leads to degradation of electrolyte membrane because of little water content. Therefore, drying process has to be optimized. In this study, various GDL structure with unique fiber orientation were simulated by numerical analysis, and the real GDL structure was reconstructed by X-ray CT image of carbon paper GDL. Next, our past two-phase network model was improved to include phase change effect. The multi-block two-phase network model based on an actual structure was developed by a direct 3D networking porous structure. As results, the evaporation interface area depended on the porous structure of GDL, and the overall evaporation rate of homogeneous GDL which has uniform structure was 1.5 time higher than that of heterogeneous GDL because of the difference of this interface area. In addition, in the case of rib and channel, liquid water under channel evaporated faster than that under Rib. It is very important to control the drying operation in order to prevent the excess membrane drying.

In fuel cell technologies, there are some problems which should be overcome rapidly. For example, it is known that voltage losses in polymer electrolyte fuel cells are serious problems. However, drastic solutions have not been found out yet. In the present study, we experimentally try to improve the energy conversion efficiency, focusing on ion currents in electrode membrane assemblies (MEAs). Additional Ag electrodes are fabricated on an MEA and their effects on proton flows are investigated. Consequently, it is found that electric voltage losses can be suppressed by electric or ion currents parallel to the proton flow. This result suggests that the external perturbations can be effective to protons and oxygen molecules on their reactions and on the power generation efficiency.

A serpentine flow channel is one of the most common and practical channel layouts for PEFCs since it ensures the removal of water produced in the cell with an acceptable parasitic load. The operating parameters such as temperature, pressure and flow distribution in the flow channel and GDL has a great influence on the performance of PEFCs. It is desired to have an optimum pressure drop because a certain pressure drop helps to remove excess liquid water from the fuel cell, too much of pressure drop would increase parasitic power needed for the pumping air through the fuel cell. In order to accurately estimate the pressure drop precise calculation of mass conservation is necessary. Flow crossover in the serpentine channel and GDL of PEFC has been investigated by using a transient, non-isothermal and three-dimensional numerical model. Considerable amount of cross flow through GDL is found and its influence on the pressure variation in the channel is identified. The results obtained by numerical simulation are also compared with the experimental as well as theoretical solution.

These days Polymer Electrolyte Fuel Cell (PEFC) is the most developed fuel cell. A polymer electrolyte membrane (PEM) is used in PEFC. Its efficiency is proportional to the proton transferring efficiency, which depends on the nanoscale structure of water. In this study, the property of proton transfer was analyzed by Molecular Dynamics (MD) method including Grotthus mechanism by Empirical Valence Bond (EVB) method. Nafion membrane was adopted as PEM. The potential energy barrier of proton hopping obtained by EVB method was adjusted to reproduce the energy barrier obtained by Density Functional Theory (DFT). In MD simulation, the distribution of water in Nafion was firstly analyzed. The results showed that liquid molecules gather around sulfo groups. Next, the property of proton transfer was analyzed by Mean Square Displacement (MSD).

This paper demonstrates numerical simulations of droplet on gas diffusion layer of the polymer electrolyte fuel cell. The lattice Boltzmann method for incompressible two-phase flows at high density ratios were applied for the simulations in order to precisely predict the shape and moving velocity of water droplet surrounding by the air in the gas channel. Simulations were conducted in 2D and 3D and height and moving velocity of droplet were compared with experiment as a function of mean gas velocity in the gas channel. The droplet heights by the simulations were qualitatively agreed with the experimental data, while the simulation results of moving speed of droplet somewhat overestimated the experimental results.

Synchrotron X-ray computed tomography was employed to measure the volume variation of gas diffusion layer (GDL) for polymer electrolyte fuel cell (PEFC). The study was conducted using 3D reconstruction (or a 3D rendering software) of orthoslice images. Especially, the temporal variation of structural parameters such as porosity was measured under freeze and thaw cycles. The freezing and thawing cycle were generated using a CRYO-system and an external light source alternatively. As a result, the structural parameters such varied significantly between the successive freeze/thaw cycles and irreversible change was also observed.

The MCFC system of BOP (Balance of Plant) is contained various mechanical equipments. One of the equipments of the heat exchangers is important component for efficiency and cost. In MCFC system, several heat exchangers are used according to the application. Most typical heat exchanger is the humidifier in BOP for MCFC, which is named for the humidifier because it is to preheat the fuel and water so that a reactor will convert some of the incoming fuel to hydrogen. Then, hot side fluid service is used the exhausted gas from the fuel cell and cold side fluid service is the fuel and water. The operation temperature range is about 25∼500 Celsius Degree.[1] This heat exchanger has the problems of multiphase fluid and phase change heat transfer. So it is necessary to analyze the heat transfer characteristics and to propose the reasonable design methodology for the humidifier. In this study, the thermal characteristic for the humidifier is estimated by using commercial tool of heat exchanger design, rating and simulation. Also this study presents the results for test facility of fabrication and for testing.

Fuel cells are considered to be one of the main sources of future power supply around the world because of their many desirable features; technology virtually free of pollution, the ability to use alternative fuels other than fossil fuels, and higher efficiencies than combustion engines. Solid Oxide Fuel Cells (SOFCs) can operate on a wide range of fuels, particularly with coal syngas. However, several issues have to be solved before SOFC’s operating on coal syngas can be introduced into the market as a reliable and cost viable technology. Numerical simulations can be used in conjunction with experiments to assist in resolution of such barriers. In the present work, a three-dimensional model is used to study the performance of a SOFC running on coal syngas operating at various conditions. The code is capable of simulating several species in the fuel stream, such as methane, steam, carbon monoxide, hydrogen, carbon dioxide. Due to the presence of hydrogen and carbon monoxide, simultaneous electrochemical oxidation of both fuels is considered. Internal reforming and water gas shift reaction are other processes that are taken into account. Simulations of typical anode-supported button cells are performed to assess the effects of cell operating temperature, fuel composition and CO electrochemistry on the performance of the button SOFCs.

The paper presents the results of investigation about flow distribution and uniformity of flow fields in three types of flow distributors with novel design. The flow distributors have a number of bifurcations to split one flow into a number of sub-streams of equal flow rates on a bipolar plate which may accommodate the electrochemical reaction in a fuel cell. There are three types of bifurcation structures studied, which are the 90° tee-type, rounded-type, and slanted-type. Numerical analysis and experimental test was conducted to investigate the flow uniformity in a multiple channels that come from several stages of bifurcations. Pressure drops of the whole flow field from inlet to outlet of the bipolar plates were also studied in the numerical simulation. Overall evaluation of flow uniformity and pressure drops in the three designs was also conducted.