Browsing by Author "Chen, Falin"

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An analytical solution for transport of oxygen in cathode gas diffusion layer of PEMFC
(2006-09-29)
Tsai, C. R.
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Chen, Falin
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Ruo, A. C.
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Chang, Min-Hsing
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Chu, Hsin-Sen
A two-dimensional theoretical model is developed in this study to simulate the transport phenomena of oxygen in cathode gas diffusion layer (GDL) of proton exchange membrane fuel cell (PEMFC). An analytical solution is then obtained accordingly to characterize the effects of GDL on cell performance. It is found that the concentration flux of oxygen across the GDL is primarily dominated by the thickness and porosity of GDL. For a thicker GDL, the diffusion resistance increases and thus lowers the cell performance especially under high current density condition. On the other hand, an increase of porosity will enhance the transport of oxygen and result in significant improvement of cell performance. The influences of system parameters including the temperature, channel height, inlet velocity, and inlet pressure on the diffusion of oxygen in GDL are also examined systematically. Results provide insights into the characteristics of oxygen diffusion in GDL and benefit the optimal design of PEMFC. (c) 2006 Elsevier B.V. All rights reserved.
Analysis of a Plate-Type Microreformer for Methanol Steam Reforming Reaction
(2009-10-01)
Chen, Falin
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Chang, Min-Hsing
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Kuo, Chih-Yi
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Hsueh, Ching-Yi
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Yan, We-Mon
A numerical simulation is performed in this study for a plate-type microreactor with parallel microchannels and diagonal inlets/outlets. The methanol steam reforming reaction is considered, and the performance is evaluated by examining the concentration profiles of methanol, hydrogen, And carbon monoxide within the rector under various operating conditions, including the influences of the steam/carbon (S/C) ratio, reaction temperature, and liquid feed rate. Particularly, the effect of aspect ratio of the microchannel on the methanol conversion rate, hydrogen generation rate, and mole fraction of carbon monoxide in the outlet gas mixture are also explored. The results show that such a plate-type design of methanol microreformer may cause nonuniform reaction states in each microchannel and affect its reforming performance significantly. It is found that these concentration nonuniformities are heavily dependent on the reaction temperature, S/C ratio, and liquid feed rate. The numerical model provides an efficient way to characterize the reforming reactions within the reactor, and the results will benefit the future design for a plate-type methanol microreformer.
Effects of chlorides on the performance of proton exchange membrane fuel cells
(2011-05-01)
Yan, Wei-Mon
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Chu, Hsin-Sen
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Liu, You-Lun
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Chen, Falin
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Jang, Jer-Huan
This paper investigates the effects of cathode gases containing chloride ions on the proton exchange membrane fuel cell (PEMFC) performance. Chloride solutions are vaporized using an ultrasonic oscillator and mixed with oxygen/air. The salt concentration of the mixed gas in the cathode is set by varying the concentration of the chloride solution. Five-hour tests show that an increase in the concentration of sodium chloride did not significantly affect the cell performance of the PEMFC. It is found that variations in the concentration of chloride do not show significant influence on the cell performance at low current density operating condition. However, for high current density operating conditions and high calcium chloride concentrations, the chloride ion appears to have a considerable effect on cell performance. Experimental results of 108-h tests indicate that the fuel cell operating with air containing calcium chloride has a performance decay rate of 3.446 mV h(-1) under the operating condition of current density at 1 A/cm(2). From the measurements of the I-V polarization curves, it appears that the presence of calcium chloride in the cathode fuel gas affects the cell performance more than sodium chloride does. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Reactant gas transport and cell performance of proton exchange membrane fuel cells with tapered flow field design
(2006-07-14)
Liu, H. C.
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Yan, W. M.
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Soong, C. Y.
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Chen, Falin
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Chu, H. S.
The objective of this work is to examine the reactant gas transport and the cell performance of a proton exchange membrane fuel cell (PEMFC) with a tapered flow channel design. It is expected that, with the reduction in the channel depth along the streamwise direction, the reactant fuel gas in the tapered channel can be accelerated as well as forced into the gas diffuser layer to enhance the electrochemical reaction and thus augment the cell performance. The effects of liquid water formation on the reactant gas transport are taken into account in the present study. Numerical predictions show that the cell performance can be enhanced with the fuel channel tapered, and the enhancement is more noticeable at a lower voltage. The results also reveal that the liquid water effect in general influences the cell performance and the effect becomes significant at lower voltages. (c) 2005 Elsevier B.V. All rights reserved.
Transient analysis of water transport in PEM fuel cells
(2006-11-22)
Yan, Wei-Mon
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Chu, Hsin-Sen
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Chen, Jian-Yao
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Soong, Chyi-Yeou
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Chen, Falin
This paper theoretically studies the water transport phenomena in PEM fuel cells, mainly investigating the transient behavior in the gas diffusion layer (GDL), catalyst layer (CL) and proton exchange membrane (PEM). In the PEM, both diffusion and electro-osmosis processes are considered, while in the GDL and CL, only diffusion process is taken into account. The process of water uptake is employed to account for the water transport at the interface between the PEM and CL. The results indicate that the water content in the PEM and the time for reaching the steady state in the start-up process are influenced by the humidification constant, k, the humidification, and the thickness of PEM. The rise of the k increases the water content in the membrane and shortens the time for reaching the steady state. Insufficient humidification causes relatively small water content and long steady time. When the PEM is thinner, the water is more uniformly distributed, the water content gets higher, and the time for reaching the steady state is distinctly shorter. (c) 2006 Elsevier B.V. All rights reserved.