Browsing by Author "Chang, Min-Hsing"

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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.
Numerical study of heat and mass transfer in the plate methanol steam micro-reformer channels
(2010-08-01)
Hsueh, Ching-Yi
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Chu, Hsin-Sen
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Yan, Wei-Mon
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Chen, Chiun-Hsun
;
Chang, Min-Hsing
Effects of geometric and thermo-fluid parameters on performance and heat and mass transfer phenomena in micro-reformer channels were investigated by mathematical modeling. The geometric parameters considered were the channel length, channel height, catalyst thickness and catalyst porosity, while the thermo-fluid parameters included wall temperature, inlet fuel temperature, fuel ratio and Reynolds number. The results of the modeling suggest that the methanol conversion could be improved by 49%-points by increasing the wall temperature from 200 degrees C to 260 degrees C. The results also show that the CO concentration would be reduced from 1.72% to 0.95% with the H(2)O/CH(3)OH molar ratio values ranging from 1.0 to 1.6. The values of parameters that enhance the performance of micro-reformer were identified, such as longer channel length, smaller channel height, thicker catalyst layer, larger catalyst porosity, lower Reynolds number and higher wall temperature. (C) 2010 Elsevier Ltd. All rights reserved.