• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.34-40
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• 2015

A stack in the proton exchange membrane fuel cell (PEMFC) consists of bipolar plates, a membrane electrode assembly, a gas diffusion layer, a collector and end plates. High current density is usually obtainable partially from uniform temperature distribution in the fuel cell. A size optimization method considering the thermal expansion effect of stacked plates was developed on the basis of finite element analyses. The thermal stresses in end, bipolar, and cooling plates were calculated based on temperature distribution obtained from thermal analyses. Finally, the optimization method was applied and optimum thicknesses of the three plates were calculated considering both fastening bolt tension and thermal expansion of each unit cell (72 cells, 5kW). The optimum design considering both thermal and mechanical loads increases the thickness of an end plate by 0.64-0.83% the case considering only mechanical load. The effect can be enlarged if the number of stack increases as in an automotive application to 200-300 stacks.

• Bulletin of the Korean Chemical Society
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• v.27 no.2
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• pp.281-285
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• 2006

Microbial fuel cells (MFC) stacked with bipolar plates have been constructed and their performance was tested. In this design, single fuel cell unit was connected in series by bipolar plates where an anode and a cathode were made in one graphite block. Two types of bipolar plate stacked MFCs were constructed. Both utilized the same glucose oxidation reaction catalyzed by Gram negative bacteria, Proteus vulgaris as a biocatalyst in an anodic compartment, but two different cathodic reactions were employed: One with ferricyanide reduction and the other with oxygen reduction reactions. In both cases, the total voltage was the mathematical sum of individual fuel cells and no degradation in performance was found. Electricity from these MFCs was stored in a supercapacitor to drive external loads such as a motor and electric bulb.

• Journal of Korea Foundry Society
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• v.31 no.2
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• pp.71-78
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• 2011

This study aims to investigate the formability of bipolar plates for fuel cell fabricated by vacuum die casting of ALDC 6. Cavity shape of mold is thin walled plate (size: $200mm{\times}200mm{\times}0.8mm$) with a serpentine channel (active area: $50mm{\times}50mm$). Before bipolar plate was made by HPDC, computational filling behavior and solidification was performed by MAGMA soft. The final mold design for location and direction of channel was determined by computational simulation. Also, according to injection speed conditions, simulation result was compared to actual die casting experimental result. When vacuum pressure, injection speed of low and high region is 350 mbar, 0.3 m/s and 2.5 m/s respectively, products had few casting defects. On the other hand, at the same as injection speed, without vacuum pressure, products had many casting defects between end of the channel and overflow.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.65-74
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• 2012

In this paper, we present the results of our studies on optimal die design towards development of a vacuum die casting process to fabricate fuel cell bipolar plate with micro-channel array. Cavity and overflow shape is designed by computational filling analysis of MAGMA soft. Optimal die design consists of seven overflows at the end of cavity and three overflows at each side wall of cavity. The molten metal that passed the gate and reached the side wall flowed into the side overflow, no turbulent flow occurred, and the filling behavior and velocity distribution were uniform. In addition, partially solidified molten metal passing through the channel was perfectly eliminated by overflow without back-flow. When vacuum pressure, injection speed of low and high region was 300 mbar, 0.3 m/s and 2.5 m/s respectively with Silafont 36 die casting alloy, sound sample without casting defects was obtained. The experimental results are nearly consistent with simulation results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4673-4678
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• 2011

In this paper, studies on a mixing characteristic and viscosity measurement of polymer/graphite composites for a bipolar plate of the polymer electrolyte membrane fuel cell were presented. Since the materials for the bipolar plate should be electrically conductive, contents of solid graphite in the composite are very high. As a consequence, a viscosity of the polymer/graphite composite used for the bipolar plate is very high and the measurement of the viscosity is difficult. Viscosity measurements of the polymer/graphite composites were not possible because pressure drops were continuously fluctuated during the viscosity measurements when a conventional capillary die was used. After the die design was optimized, the steady state pressure drop could be achieved, but the viscosity thus measured was not reproducible. After many trials with different experimental techniques, it was found that melt blending of the grinded powder mixtures of both PET and graphite provides reproducible viscosity measurements and electric conductivities of the polymer/graphite composites.

• 한국전기화학회:학술대회논문집
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• 2004.06a
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• pp.169-172
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• 2004

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.29-35
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• 2016

It is important to uniformly supply the fuel gas into the reaction activity area in polymer electrolyte membrane fuel cell (PEMFC). Recent studies have shown that the cell performance can be significantly improved by employing metal foam gas distributor as compared with the conventional bipolar plate types. The metal foam gas distributor has been reported to be more efficient to fuel transport. In this study, three-dimensional computational fluid dynamics (CFD) simulations have been performed to examine the effects of metal foam flow field design on the fuel supply to the reaction site. Darcy's law is used for the flow in the porous media. By solving additional advection equation for fluid particle trajectory, the gas transport has been visualized and examined for various geometrical configuration of metal foam gas distributor.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.39-46
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• 2006

The fuel cell is one of promising environment-friendly energy sources for the next generation. The bipolar plate is a major component of the PEM fuel cell stack, which takes a large portion of stack cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity To achieve desired electrical properties, specimens made with different mixing ratio, processing pressure and temperature were tested. To increase mechanical strength, one or two layers of woven carbon fabric were added to the graphite and resin composite. Thus, the composite material was consisted of three phases: graphite particles, carbon fabric, and epoxy resin. By increasing mixing ratio of graphite, fabricated pressure and process temperature, the electric conductivity of the composite was improved. The results of tensile test showed that the tensile strength of the two-phase graphite composite was about 4MPa, and that of three-phase composite was increased to 57MPa. As surface properties, contact an91e and surface roughness were tested. Graphite composites showed contact angles higher than $90^{\circ}$, which mean low surface energy. The average surface roughness of the composite specimens was $0.96{\mu}m$.

• 한국항공운항학회:학술대회논문집
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• 2005.11a
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• pp.227-232
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• 2005

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.456-461
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• 2003

A fuel cell is an electrochemical device in which the energy of a chemical reaction is converted directly into electricity. By combining hydrogen fuel with oxygen from air, electricity is formed, without combustion of any form. Water and heat are the only by-products when hydrogen is used as the fuel source. Fuel cell stack consists of multi-layered unit cells. A unit cell consists of MEA and bipolar plates. The end plate of fuel cell stack should give a uniform distributed pressure to multi unit cell layers so as to reduce the contact resistance and to prevent the leakage of reactant gases and the damage of multi layer components. The current end plate is redundantly large and heavy. It makes the power per unit volume reduced. Topology optimization of end plate is conducted for mass reduction and enhancement of bending rigidity. The evaluation of the current design and the recommendation for the future design is remarked.