In this thesis the numerical method is adopted to study the flow characteristics of reactants, when the newly developed heterogeneous composite carbon bipolar plate and the traditional hard surface bipolar plate are applied to fuel cells. The simulation in this study includes the distributions of the velocity and pressure of oxidizers flowing in a parallel or serpentine flow channel under several inlet gas flow rates and pressures. The difficulty to supply reactant to the active area under the ribs is also studied in this thesis. From these studies we can understand the strong and weak points of the newly developed bipolar plates and the traditional bipolar plates better.
The simulation results display that the gaseous reactants or products can permeate through the gaps between carbon fibers into or out of active area under the rib, which is formed with carbon fiber bunches. Therefore more reactant gases can be supplied with the heterogeneous carbon fiber bipolar plates than the graphite bipolar plates. In addition, the higher efficiency of fuel cells can be obtained with the new plate, especially in high power density. The pressure distribution in making use the heterogeneous carbon fiber bipolar plates are more uniform, and the pressure drop is also less than the traditional bipolar plates. For large fuel cells the current distribution will be more uniform and the pumping power will be less. The reactant gases can flow through the gaps of carbon fibers and the porous carbon cloth into the catalyst layers by convection and diffusion. So no matter what type of the flow channels used the needed oxidizer is much less with the new bipolar plate than with traditional one. The flow fields of the two types of bipolar plates are quite similar, but the gas needed to supply is also much less with the new plate. Because of the advantages mentioned above, we believe that the heterogeneous carbon fiber bipolar plate is better than the traditional graphite bipolar plate.
Keywords: fuel cell, heterogeneous carbon fiber bipolar plate,hard surface bipolar plate
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0904106-103801 |
| Date | 04 September 2006 |
| Creators | Wang, Chi-yin |
| Contributors | Ming-San Lee, Long-Jeng Chen, none, Chorng-Fuh Liu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0904106-103801 |
| Rights | not_available, Copyright information available at source archive |
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