• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.78-85
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• 2006

Selection of flow channel in the separation plate of PEMFC is very important parameter to improve its performance and reduce parasite loss. Flow patterns in the channel have great influence on the transport of hydrogen and air and removal of water generated from electrochemical reaction in diffusion layer. In this study. fluid flow in flow channel with parallel and interdigitated patterns are simulated three dimensionally on full flow domain including anode and cathode channel together. The numerical results show that the fuel cell with interdigitated flow channel represents better performance than that with parallel flow channel due to its strong convective transport across the gas diffusion layer. But the pressure drop in parallel flow channel is much more than that in interdigitated flow channel. And effects of temperature and stoichiometric number on performance can be calculated and analyzed as well. Nomenclature.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.193-198
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• 2003

A gas turbine blade has an internal cooling passage equipped with ribs, which can be modeled as a ribbed channel. We have studied a flow inside a ribbed channel using large eddy simulaton (LES) with a dynamic subgrid-scale model. The simulation results are compared with the experimental ones. The turbulence intensity and local heat transfer near the rib have not been well captured by the conventional Reynolds averaged Navier-Stokes simulation (RANS). However, these variables obtained by the present LES agree well with those from experiments. From the instantaneous velocity and temperature fields, we explain the mechanisms responsible for the local peaks in the heat transfer distribution along the channel wall. We have also investigated the effect of rotation on the flow and heat transfer in the ribbed channel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.3
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• pp.439-447
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• 2002

The microchannel flow in miniature TCDs (thermal conductivity detectors) is investigated numerically. The solutions based on the boundary layer approximation are not very accurate in the region of the duct inlet for low Reynolds numbers. In this study, two-dimensional Navier-Stokes equations are considered to analyze the gas flow in a miniature TCD. Effects of channel size, inlet and boundary conditions on the heat transfer rate are examined. When the gas stream is not preheated, the distances for a miniature TCD to reach the conduction-dominant region for duct flow are found to be approximately two and three times the thermal entry length for duct flow with constant properties, respectively, leer constant wall temperature and constant wall heat flux boundary conditions. If the gas temperature at the channel inlet is close to the mean gas temperature in the conduction-dominant region, the entrance region is much shorter compared to other cases considered in this study.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.63-70
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• 2022

Compared with hydrogen, ammonia has the advantages of high gravimetric hydrogen densities (17.8 wt.%), ease of storage and transportation as a chemical hydrogen storage medium, while its application in small-scale on-site hydrogen production scenarios is limited by the need for complex separation equipment during high purity hydrogen production. Therefore, the study of PEMFC, which can directly utilize ammonia decomposition gas, can greatly expand the application of fuel cells. In this paper, the output characteristics, fuel efficiency and the variation trend of hydrogen concentration and local current density in the anode channel of fuel cell with the output voltage of PEMFC fueled by ammonia decomposition gas were studied by experiment and simulation. The results indicate that the maximum output power of the hybrid fuel decreases by 9.6% compared with that of the pure hydrogen fuel at the same inlet hydrogen equivalent. When the molar concentration of hydrogen in the anode channel is less than 0.12, the output characteristics of PEMFC will be seriously affected. Employing ammonia decomposition gas as fuel, the efficiency corresponding to the maximum output power of PEMFC is approximately 47%, which is 10% lower than the maximum efficiency of pure hydrogen.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.2
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• pp.109-115
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• 2017

Using the computational fluid dynamics (CFD) technique, we performed a numerical simulation in anodesupported solid oxide fuel cell (SOFC). The effect of gas channel/rib width on the cell performance and temperature uniformity was investigated in planar type SOFC. The open source CFD toolbox, OpenFOAM, was used as a numerical analysis tool. As a result, the effect of gas channel/rib width on the cell performance and temperature uniformity was not significant if the oxygen depletion is not occurring. On the other hand, the usage of a wide rib and operation at high current density may lead to performance degradation due to oxygen depletion.

• New & Renewable Energy
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• v.3 no.4
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• pp.8-15
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• 2007

Liquid water in flow channel is an important factor that limits the steady and transient performance of PEM fuel cells. A computational fluid dynamics study based on the volume-of-fluid [VOF] multi-phase model was conducted to understand the two-phase flow behavior of liquid water in cathode gas channels. The liquid water transport in $180^{\circ}{\Delta}$ bends was investigated, where the effects of surface characteristics (hydrophilic and hydrophobic surfaces], channel geometries (rectangular and chamfered corners], and air velocity in channel were discussed. The two-phase flow behavior of liquid water with hydrophilic channel surface and that with hydrophobic surface was found very different; liquid water preferentially flows along the corners of flow channel in hydrophilic channels while it flows in rather spherical shape in hydrophobic channels. The results showed that liquid water transport was generally enhanced when hydrophobic channel with rounded corners was used. However, the surface characteristics and channel geometries became less important when air velocity was increased over 10m/s. This study is believed to provide a useful guideline for design optimization of flow patterns or channel configurations of PEM fuel cells.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.407-410
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• 2006

Selection of flow channel in the separation plate of PEMFC is very important parameter to improve its performance and reduce parasite loss. Flow patterns in the channel have great influence on the transport of hydrogen and all and water generated from electrochemical reaction in diffusion layer In this study, fluid flow in flow channel with parallel and interdigitated patterns are simulated three dimensionally on full flow domain including anode and cathode electrode together. The numerical results show that the fuel cell with interdigitated flow channel represents better performance than that with parallel flow channel due to its strong convective transport across the gas diffusion layer. But the pressure drop in parallel flow channel is much more than that in nterdigitated flow channel. The effect of temperature and stoichiometric number on performance can be calculated and analyzed as well.

• Journal of the Korean Society of Safety
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• v.23 no.3
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• pp.1-7
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• 2008

As a clean fuel, LNG or LPG is widely used in large restaurants or plants instead of coal. These fuels are easy to use and cheap. However, they are inflammable very much and easily exploded at the worst. So there are many laws and regulations legislated for the handling and usage of the gas facilities. Nevertheless, very harsh explosions occurred in several domestic or foreign places. In this paper a gas detection and alarm system was developed for large facilities. A new concept for connecting many gas detectors was proposed and based upon that a system including hardware and software have been developed and tested. Although up to 16 gas detectors apart 1 km from main controller can be connected currently, this system can be easily expanded for more detectors because each gas detector receiver communicates with main controller using industrial standard RS-485 multi drop technique. Furthermore several additive functions was included for the installation and maintenance convenience.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.4
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• pp.57-65
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• 1999

A modified gas tracer method was used to obtain reaeration coefficient from an artificial channel and a reach of Bokha stream, Ichon city. Propane was used as the tracer gas and Rhodamine-B dye as a dispersion and dulution tracer. Concentrations of propane in water sample were measured using a gas chromatograph and concentrationsof dye using UV-Spectrophotometer. To compare measured values with predicted values,commonly used 14 equations were selected . Results of this study suggested that the modified gas tracer method is a potentially useful procedure for th edetermination of reaeration cofficients. However, estimated reaeration coefficients from predictive equations were significantly different from that of this study. Therefore, when using predictive equations, careful selection of equation with consideration for hydraulic characteristics such as flow depth and average velocity, or use of newly derived predictive equation which is adequate for questioned stream would be needed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.9
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• pp.367-372
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• 2016

Gas diffusion layer (GDL) of PEMFCs plays a role that it diffuses the reactant gases to the catalyst layer on the membrane and discharge water from the catalyst layer to the channel. Physical parameters related to the mass transport of GDL are mostly from the uncompressed GDLs while actual GDLs in the assembled stacks are compressed. In this study, the relation of compression and strain of GDLs with various Polytetrafluoroethylene (PTFE) loading is measured experimentally and In-plane gas permeability is measured at the condition that the GDLs are in compressive strain. The gas permeability decreased with the loading of PTFE and the presentation of gas permeability under compressive stain is expected to improve the accuracy of modeling work of mass transport in the GDL.