• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.195-206
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• 2003

Polymer electrolyte membrane fuel cells(PEMFC) are very interesting power source due to high power density, simple construction and operation at low temperature. But they have problems such as high cost, improvement of performance and effect of temperature. This problems can be approached using mathematical models which are useful tools for analysis and optimization of fuel cell performance and for heat and water management, in this paper, transient model consists of various energy terms associated with fuel cell operation using the mass and energy balance equation. And water transfer in the membrane is composed of back diffusion and electro-osmotic drag. The temperature calculated by transient model approximately agreed with the temperature measured by experiment in constant current condition.

• Journal of the korean Society of Automotive Engineers
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• v.26 no.3
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• pp.6-11
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• 2004

연료전지에서 반응에 참여하는 주된 연료는 수소이며, 따라서 연료전지 자동차에 사용되는 고분자전해질 연료전지(Polymer Electrolyte Membrane Fuel Cell. PEMFC)에도 연료로서 수소를 공급해야 한다. 1㎾급 연료전지의 경우 한 시간에 약 1㎥($25^{\circ}C$, 1기압)의 수소를 필요로 하므로, 수십 ㎾ 용량의 자동차용 연료전지에는 수십 ㎥/h의 빠른 속도로 수소를 공급할 수 있는 장치가 필요하다. 또한 이러한 수소 공급 속도를 유지하면서 1회 연료 충전으로 수백 km를 자동차가 주행할 수 있도록 충분한 양의 연료가 자동차 내에 저장되어 있어야 편리할 것이다. (중략)

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.16-22
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• 2024

Polymer electrolyte membrane fuel cells have the advantage of low operating temperatures and fast startup and response characteristics compared to others. Simulation studies are actively researched because their cost and time benefits. In this study, the resistance of water residual in the gas diffusion layer (GDL) of the unit cell was added to the existing equation to compare the actual data with the model data. The experiments were conducted with a 25 cm² unit cell, and the samples were separated into stopping times of 0, 10, and 60 minutes following primary impedance measurement, activation, and polarization curve data acquisition. This gives 0, 10, and 60 minutes for the residual water in the GDL to evaporate. Without the rest period, the magnitude of the performance improvement was not significantly different at the same potential and flow rate, but the rest period did improve the performance of the membrane electrode assembly when measuring impedance. By changing the magnitude of the resistance reduction to an overvoltage, the voltage difference between the fuel cell model with and without residual water was compared, and the error rate in the high current density region, which is dominated by concentration losses, was reduced.

• Journal of Powder Materials
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• v.18 no.1
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• pp.1-13
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• 2011

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.129.1-129
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• 2003

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2250-2254
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• 2007

Comprehensive analytical models focusing on the anode water loss, the cathode flooding, water equilibrium, and water management strategy are developed for polymer electrolyte fuel cells. Analytical solutions presented in this study are compared with two-dimensional computational results and shows a good agreement in predicting those critical characteristics of water. General features of water concentration profile as a function of membrane thickness and current density are presented to illustrate the net effect of the back-diffusion of water from the cathode to anode and the water production by the cathode catalytic reaction on water transport over a fuel cell domain. As one of practical applications, the required humidity level of feed streams for full saturation at the channel outlets are investigated as a function of the physical operating condition. These analytical models can provide good understanding on the characteristic water

• Journal of the Korean Electrochemical Society
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• v.18 no.2
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• pp.75-80
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• 2015

Multi-block sulfonated poly(arylene ether sulfone) (SPAES) copolymer was synthesized via nucleophilic aromatic substitution reaction for proton exchange membrane fuel cell application. After synthesizing the hydrophilic and hydrophobic precursor oligomers having different end-groups (F-terminated or OH-terminated), the effect of end group on the molecular weight was investigated. Hydrophilic oligomers with hydroquinone showed better performance as fuel cell membranes. SPAES membranes showed comparable proton conductivity to that of Nafion at $80^{\circ}C$ and above 70% RH. In particular, SPAES 9 with hydroquinone showed higher proton conductivity than SPAES 10 in the whole RH range studied. Increased local concentration of sulfonic acids within hydrophilic block might develop the hydrophilic-hydrophobic phase separation in the block copolymers.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.523-530
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• 2019

For the low-Pt electrodes for polymer electrolyte fuel cells (PEMFCs), the optimization of ionomer content for anode catalyst layers was carried out. A commercial catalyst of 20 wt.% Pt/C was used instead of 50 wt.% Pt/C which is commonly used for PEMFCs. The ionomer content varies from 0.6 to 1.2 based on ionomer to carbon ratio (I/C) and the catalyst layer is formed over the electrolyte by the ultrasonic spray process. Evaluation of the prepared MEA in the unit cell showed that the optimal ionomer content of the air electrode was 0.8 on the I/C basis, while the hydrogen electrode was optimal at the relatively high ionomer content of 1.0. In addition, a large difference in cell performance was observed when the ionomer content of the hydrogen electrode was changed. Increasing the ionomer content from 0.6 to 1.0 by I/C in a hydrogen electrode with 0.05 mg/㎠ platinum loading resulted in more than double cell performance improvements on a 0.6 V. Through the analysis of various electrochemical properties in the single cell, it was assumed that the change in ionomer content of the hydrogen electrode affects the water flow between the hydrogen and air electrodes bounded by the membrane in the cell, which affects the overall performance of the cell. A more specific study will be carried out to understand the water flow mechanism in the future, and this study will show that the optimization process of hydrogen electrode can also be a very important cell design variable for the low-Pt and high-performance MEA.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.4
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• pp.481-487
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• 2011

A fuel cell vehicle using a polymer electrolyte membrane fuel cell (PEM FC) as power source produces electric power by consuming the fuel, hydrogen. The unconsumed hydrogen is recirculated and reused to gain higer stack efficiency and to maintain the humidity in the anode side of the stack. So it is needed considering fuel efficiency to recirculated hydrogen. In this study, the indirect hydrogen recirculation flow rate measurement method for fuel cell vehicle is presented. By modeling of a convergent nozzle ejector and a hydrogen recirculation blower for the hydrogen recirculation of a PEM FC, the hydrogen recirculation flow rate was calculated by means of the mass balance and heat balance at Anode In/Outlet.

• Journal of Power System Engineering
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• v.13 no.3
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• pp.11-19
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• 2009

This paper introduces a conceptual design of a combined scroll expander-compressor unit for a fuel cell. Since air discharged out of the fuel cell stack has still high pressure energy, some power can be extracted from the air by directing it to pass through an expanding device. Such extracted power can be used to drive an auxiliary compressor. For this purpose, a scroll type expander coupled to a scroll type compressor was designed for a 1kW-class fuel cell. The orbiting scroll members of the expander and the compressor were made to share three of common drive shafts installed in the mid frame plate. Performance analysis for the combined expander-compressor unit showed that the installation of this unit could reduce the auxiliary power consumption in the fuel cell by about 42%.