本論文之研究主要針對固態氧化物燃料電池 (Solid Oxide Fuel Cell, SOFC) 中之雙極板 (interconnect)，藉由數值軟體建立3D模型並搭配蛇型、雙蛇型、歧管型及棋盤型四種流道設計，分析電池內部之氣體流場與性能輸出之相互關係。流道設計目標為使燃料均勻分佈及促進電化學反應，以提升輸出效能；並探討因電化學反應所產生之溫度變化，以期能減少溫度差，降低熱應力並延長材料壽命。
模擬結果顯示，流道設計對於燃料的濃度分佈影響甚巨，並且在不同熱傳邊界條件下產生不同的效應。由於各流道設計只有在高電流密度下操作才有性能上的差異，因此在絕熱條件及電流密度不高的情形下，各流道所表現之性能相當接近。當電池在等溫條件及高入口燃料濃度下操作，隨著電流密度的提升，雙蛇型與棋盤型流道開始有較較佳的性能表現。研究中並發現當電流密度甚小時，流道間隔與電極接觸處有較低的ohmic overpotential，因此電極表面上電流分佈將集中在較寬的流道間距上；在高電流密度時，因燃料濃度分佈不均，所以電極表面上電流分佈便開始由燃料濃度分佈所主導。熱傳方面，電化學反應所生成的熱量，在絕熱邊界條件下，只能藉由反應剩餘的反應物及生成物帶走熱量，這使得電池內部溫度大大提升。電流密度由低至高，電池內部溫度差異可達800 K。在微小尺度中，傳統使用的蛇型流道在性能上並無較為優秀的表現，但流道內的壓降卻遠遠超越其它流道設計，這對於氣體輸送成本相當不利。歧管型與棋盤型流道在流道壓降上表現較佳，在高燃料濃度下操作的性能表現比起其它兩種流道設計也不惶多讓。唯獨此兩流道設計容易受到氧氣質量分量的影響，因此當使用此兩種流道時，需對流道內的氧氣質量分量加以控制。

In this study, the impacts of flow channel design of interconnect on the performance of microscale SOFC (Solid Oxide Fuel Cell) are evaluated through cell-level simulation with a commercial software package CFD-ACE. Four different flow pattern archetypes are examined: serpentine, double serpentine, staggered cylinder, and diagonal rib. Co-flow configuration is applied for fuel delivery in this investigation. To keep the ohmic loss in the same order for all four archetypes, the ratio of interconnect contact area (rib) to channel projection area is approximately 0.5. The influences of the different flow pattern designs on the distributions of the reactant concentrations, temperature, and current density are discussed.
The performance differences of the four archetypes are only distinguishable at high current density. Under adiabatic condition, high temperature inside the cell decreases EMF and results in less than 3% discrepancies on the polarization curves for all four archetypes. Under isothermal condition, EMF is a constant and SOFC is capable of producing more power. When SOFCs are operated at high output voltage, electrons are accumulated at the bottom of wider rib and current density distribution is not relevant to fuel distribution. On the contrary, fuel distribution plays a significant role on current density pattern at low output voltage. The variations of the pressure drop are mainly caused by different flow characteristics of the flow channel designs and affect the cost for fuel delivery. Serpentine channel results in largest pressure drop comparing to other archetypes. Although the pressure drops in diagonal rib and staggered cylinder archetypes are much lower than serpentine and double serpentine design, they tend to be more sensitive to fuel concentration and their performance is detracted with low mass fraction of oxygen supply.

[1] J. Larmine and A. Dicks, Fuel Cell Systems Explained, 1st ed. West Sussex: John Wiley & Sons, 2000.
[2] G. Hoogers, Fuel Cell Technology Handbook, 1st ed. Boca Raton: CRC Press, 2003.
[3] F. Issacci, "Thermal management and transport phenomena in fuel cell system - practical issues," presented at The 6th ASME-JSME Thermal Engineering Joint Conference, March 16-20, Torrance, California, 2003.
[4] C. S. Montross, H. Yokokawa, and M. Dokiya, "Thermal stresses in planar solid oxide fuel cells due to thermal expansion differences," British Ceramic Transactions, vol. 101, pp. 85-93, 2002.
[5] J. R. Ferguson, J. M. Fiard, and R. Herbin, "Three-dimensional numerical simulation for various geometries of solid oxide fuel cells," Journal of Power Sources, vol. 58, pp. 109-122, 1996.
[6] P. L. Hentall, J. B. Lakeman, G. O. Mepsted, P. L. Adcock, and J. M. Moore, "New materials for polymer electrolyte membrane fuel cell current collectors," Journal of Power Sources, vol. 80, pp. 235-241, 1999.
[7] H. Yakabe, M. Hishinuma, M. Uratani, Y. Matsuzaki, and I. Yasuda, "Evaluation and modeling of performance of anode-supported solid oxide fuel cell," Journal of Power Sources, vol. 86, pp. 423-431, 2000.
[8] H. Yakabe, T. Ogiwara, M. Hishinuma, and I. Yasuda, "3-D model calculation for planar SOFC," Journal of Power Sources, vol. 102, pp. 144-154, 2001.
[9] K. P. Recknagle, R. E. Williford, L. A. Chick, D. R. Rector, and M. A. Khaleel, "Three-dimensional thermo-fluid electrochemical modeling of planar SOFC stacks," Journal of Power Sources, vol. 113, pp. 109-114, 2003.
[10] J. Yuan, M. Rokni, and B. Sunden, "Three-dimensional computational analysis of gas and heat transport phenomena in ducts relevant for anode-supported solid oxide fuel cells," International Journal of Heat and Mass Transfer, vol. 46, pp. 809-821, 2003.
[11] Z. Lin, J. W. Stevenson, and M. A. Khaleel, "The effect of interconnect rib size on the fuel cell concentration polarization in planar SOFCs," Journal of Power Sources, vol. 117, pp. 92-97, 2003.
[12] A. Kumar and R. G. Reddy, "Effect of channel dimensions and shape in the flow-field distributor on the performance of polymer electrolyte membrane fuel cells," Journal of Power Sources, vol. 113, pp. 11-18, 2003.
[13] C. W. Tanner and A. V. Virkar, "A simple model for interconnect design of planar solid oxide fuel cells," Journal of Power Sources, vol. 113, pp. 44-56, 2003.
[14] B. A. Haberman and J. B. Young, "Three-dimensional simulation of chemically reacting gas flows in the porous support structure of an integrated-planar solid oxide fuel cell," International Journal of Heat and Mass Transfer, vol. 47, pp. 3617-3629, 2004.
[15] F. J. Gardner, M. J. Day, N. P. Brandon, M. N. Pashley, and M. Cassidy, "SOFC technology development at Rolls-Royce," Journal of Power Sources, vol. 86, pp. 122-129, 2000.
[16] S. W. Cha, R. O'Hayre, S. J. Lee, Y. Saito, and F. B. Prinz, "Geometric scale effect of flow channels on performance of fuel cells," Journal of the Electrochemical Society, vol. 151, pp. A1856-A1864, 2004.
[17] S. W. Cha, R. O'Hayre, Y. Saito, and F. B. Prinz, "The scaling behavior of flow patterns: A model investigation," Journal of Power Sources, vol. 134, pp. 57-71, 2004.
[18] J. A. Rock, "Converging/Diverging flow channels for fuel cell", U.S. Patent 6699614 B2, March 2, 2004.
[19] Nicholas G. Vitale, "Fluid flow plate for decreased density of fuel cell assembly", U.S. Patent 5981098, November 9, 1999.
[20] M. H. Nelson, "Fuel cell channel distribution for hydration water", U. S. Patent 6303245 B1, October 16, 2001.
[21] S. J. Granata and B. M. Woodle, "Fuel cell plates with skewed process channels for uniform distribution of stack compression load", U.S. Patent 4853301, August 1, 1989.
[22] J. A. Rock, "Mirrored serpentine flow channels for fuel cell", U.S. Patent 6099984, August 8, 2000.
[23] J. A. Rock, "Serially-linked serpentine flow channels for PEM fuel cell", U.S. Patent 6309773 B1, October 30, 2001.
[24] H. H. Voss and C. Y. Chow, "Coolant flow field plate for electrochemical fuel cells", U.S. Patent 5230966, July 27, 1993.
[25] X. REN and S. Gottesfild, "Flow channel device for electrochemical cells", W.O. Patent 01/48852 A1, July 5, 2001.
[26] V. Gurau, F. Barbir, and Jay K. Neutzler, "Fuel cell collector plates with improved mass transfer channels", U.S. Patent 6551736 B1, April 22, 2003.
[27] Y. S. Yoo, H. C. Lim, J. W. Park, and S. H. Park, "Solid oxide fuel cells having gas channel", U.S. Patent 2004/0091766 A1, May 13, 2004.
[28] K. B.Oldham and J. C. Myland, Fundamentals of Electrochemical Science. San Diego: Academic Press, Inc., 1994.
[29] F. M. White, viscous fluid flow, 2nd ed. New York: McGraw-Hill, Inc., 1991.
[30] B. E. Poling, J. M. Prausnitz, and J. P. O'Connell, The Properties of Gases and Liquids, 5th ed. New York: McGraw-Hill, 2001.
[31] Z.-H. Yang, "Design and fabrication of the dynamic fuel evaporator for microscale power system," M.S. thesis, Department of Mechanical Engineering., National Taiwan University of Science and Technology, Taipei, 2005.
[32] Y. A. Cengel and M. A. Boles, Thermodynamics: An Engineering Approach, 4th ed. New York: McGraw-Hill, Inc., 2002.
[33] CFD-ACE+ User Manual, C. R. Corporation, Australia, 2003
[34] W. Z. Zhu and S. C. Deevi, "A review on the status of anode materials for solid oxide fuel cells," Materials Science and Engineering A, vol. 362, pp. 228-239, 2003.
[35] M. Kuznecov, P. Otschik, P. Obenaus, K. Eichler, and W. Schaffrath, "Diffusion controlled oxygen transport and stability at the perovskite/electrolyte interface," presented at 6th ISSFIT Conf., May 9-12 2001, Cracow, Poland, 2003.
[36] E. Fuel Cell Group, AIST, "Thermal and physical properties of materials for fuel cells." Available http://unit.aist.go.jp/energyelec/fuelcell/english/database/thphy1.html
[37] J.-W. Moon, H.-J. Hwang, M. Awano, and K. Maeda, "Preparation of NiO-YSZ tubular support with radially aligned pore channels," Materials Letters, vol. 57, pp. 1428-1434, 2003.
[38] T. Tsai and S. A. Barnett, "Effect of LSM-YSZ cathode on thin-electrolyte solid oxide fuel cell performance," Solid State Ionics, vol. 93, pp. 207-217, 1997.
[39] M. Iwata, T. Hikosaka, M. Morita, T. Iwanari, K. Ito, K. Onda, Y. Esaki, Y. Sakaki, and S. Nagata, "Performance analysis of planar-type unit SOFC considering current and temperature distributions," Solid State Ionics, vol. 132, pp. 297, 2000.
[40] R. M. C. Clemmer and S. F. Corbin, "Influence of porous composite microstructure on the processing and properties of solid oxide fuel cell anodes," Solid State Ionics, vol. 166, pp. 251-259, 2004.
[41] E. Wanzenberg, F. Tietz, P. Panjan, and D. Stover, "Influence of pre- and post-heat treatment of anode substrates on the properties of DC-sputtered YSZ electrolyte films," Solid State Ionics, vol. 159, pp. 1-8, 2003.