Browsing by Author "Hsueh, Ching-Yi"

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Analysis of a Plate-Type Microreformer for Methanol Steam Reforming Reaction
(2009-10-01)
Chen, Falin
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Chang, Min-Hsing
;
Kuo, Chih-Yi
;
Hsueh, Ching-Yi
;
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 a plate methanol steam micro reformer with methanol catalytic combustor
(2010-06-01)
Hsueh, Ching-Yi
;
Chu, Hsin-Sen
;
Yan, Wei-Mon
;
Chen, Chiun-Hsun
;
機械工程學系
A numerical study is performed to examine the characteristics of heat and mass transfer and the performance of a plate methanol steam micro reformer with a methanol catalytic combustor. The effects of the flow configurations for co- and counter-current flows are explored in the present study. The influences of the Reynolds number (Re) and various geometric parameters on heat and mass transfer phenomena in the channels are also investigated numerically. It is expected that the Reynolds number (Re) and various geometric parameters can be improved by thermal management to enhance the chemical reaction and thus augment the micro reformer performance. Comparing the co- and counter-current flows via numerical simulation, the results show that the methanol conversion for counter-current flow could be improved by 10%. This is due to the fact that counter-current flow leads to a better thermal management, which in turn improves fuel conversion efficiency. With a higher Reynolds number on the combustor side, the wall temperature is increased and the methanol conversion can thus be enhanced. Meanwhile, a reduced Reynolds number on the micro reformer side would increase the methanol conversion. The results also reveal that appropriate geometric parameters exist for a micro reformer with a combustor to obtain better thermal management and methanol conversion. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
Numerical study of heat and mass transfer in the plate methanol steam micro-reformer channels
(2010-08-01)
Hsueh, Ching-Yi
;
Chu, Hsin-Sen
;
Yan, Wei-Mon
;
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.
Numerical study on micro-reformer performance and local transport phenomena of the plate methanol steam micro-reformer
(2009-02-15)
Hsueh, Ching-Yi
;
Chu, Hsin-Sen
;
Yan, Wei-Mon
;
機械工程學系
;
Department of Mechanical Engineering
The objective of this work is to investigate the transport phenomena and performance of a plate steam methanol micro-reformer. Micro channels of various height and width ratios are numerically analyzed to understand their effects on the reactant gas transport characteristics and micro-reformer performance. In addition, influences of Reynolds number and geometric size of micro channel on methanol conversion of micro-reformer and gas transport phenomena are also explored. The predicted results demonstrated that better performance is noted for a micro channel reformer with lower aspect-ratio micro channel. This is due to the larger the chemical reaction surface area for a lower aspect-ratio channel reformer. It is also found that the methanol conversion decreases with increasing Reynolds number Re. The results also indicate that the smaller micro channel size experiences a better methanol conversion. This is due to the fact that a smaller micro channel has a much more uniform temperature distribution, which in turn, fuel utilization efficiency is improved for a smaller micro channel reformer. (C) 2008 Elsevier B.V. All rights reserved.
Transport phenomena and performance of a plate methanol steam micro-reformer with serpentine flow field design
(2010-10-01)
Hsueh, Ching-Yi
;
Chu, Hsin-Sen
;
Yan, Wei-Mon
;
Chen, Chiun-Hsun
;
機械工程學系
A numerical investigation of the transport phenomena and performance of a plate methanol steam micro-reformer with serpentine flow field as a function of wall temperature, fuel ratio and Reynolds number are presented. The fuel Reynolds number and H(2)O/CH(3)OH molar ratio (S/C) that influence the transport phenomena and methanol conversion are explored in detail. In addition, the effects of various wall temperatures on the plates that heat the channel are also investigated. The predictions show that conduction through the wall plays a significant effect on the temperature distribution and must be considered in the modeling. The predictions also indicate that a higher wall temperature enhances the chemical reaction rate which, in turn, significantly increases the methanol conversion. The methanol conversion is also improved by decreasing the Reynolds number or increasing the S/C molar ratio. When the serpentine flow field of the channel is heated either through top plate (Y = 1) or the bottom plate (Y = 0), we observe a higher degree of methanol conversion for the case with top plate heating. This is due to the stronger chemical reaction for the case with top plate heating. (C) 2010 Published by Elsevier Ltd.
Transport phenomena and performance of a plate methanol steam micro-reformer with serpentine flow field design
(2010-10-01)
Hsueh, Ching-Yi
;
Chu, Hsin-Sen
;
Yan, Wei-Mon
;
Chen, Chiun-Hsun
;
機械工程學系
A numerical investigation of the transport phenomena and performance of a plate methanol steam micro-reformer with serpentine flow field as a function of wall temperature, fuel ratio and Reynolds number are presented. The fuel Reynolds number and H(2)O/CH(3)OH molar ratio (S/C) that influence the transport phenomena and methanol conversion are explored in detail. In addition, the effects of various wall temperatures on the plates that heat the channel are also investigated. The predictions show that conduction through the wall plays a significant effect on the temperature distribution and must be considered in the modeling. The predictions also indicate that a higher wall temperature enhances the chemical reaction rate which, in turn, significantly increases the methanol conversion. The methanol conversion is also improved by decreasing the Reynolds number or increasing the S/C molar ratio. When the serpentine flow field of the channel is heated either through top plate (Y = 1) or the bottom plate (Y = 0), we observe a higher degree of methanol conversion for the case with top plate heating. This is due to the stronger chemical reaction for the case with top plate heating. (C) 2010 Published by Elsevier Ltd.