無膜燃料電池流場分析與性能設計

The Flow Analysis and Performance Design of Membraneless Fuel Cells

方乃祥(Nai-Siang Fang)

指導教授 ： 陳發林

國立臺灣大學/工學院/應用力學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.01631

摘要

本論文針對一新穎無膜燃料電池(Membraneless Fuel Cells)內部傳輸現象以及電池性能作一完整之分析與比較，並利用商業套裝軟體CFDRC進行模擬。研究中係以有限體積法(Finite Volume Method)求解各統御方程式，探討當改變不同操作與幾何參數時，無膜燃料電池內部之流場分布、濃度場分布以及輸出電流密度變化情形，此舉將有助於釐清各參數對整體燃料電池性能之影響，幫助實驗設計者做出最正確之判斷。
本論文研究結果得知，當流場操作條件為高裴立數(High Peclet Number)時，將有效降低濃度邊界層厚度，亦即濃度補充迅速，輸出電流密度將增加。細部來看，電池內部陰極側傳輸現象主導了整體性能變化，而陽極側傳輸現象相較之下較不明顯，故增加陰極側氧化物之濃度與擴散係數時，電池性能將大大地提升；而增加陽極燃料動黏滯係數時，陰極氧化物之裴立數也將增加，因此性能也較佳。就幾何參數來看，在固定體積流率時，縮小流道截面積將有助於裴立數之增加，進而提升電池性能；而改變截面積之長-寬比時，若能因此減少截面積並且增加裴立數，在雙重影響下，電池性能也將大幅地提升。

關鍵字

無膜 ； 燃料電池 ； 裴立數

並列摘要

This thesis is to analyze and evaluate the phenomena of the internal transmission of novel membraneless fuel cells as well as the cell performance. Relevant simulations are accomplished by commercial software CFDRC, which solves governing equations through finite volume method. Internal flow field, concentration field, and current density under different operating and geometric parameters are simulated to clarify the effects of those parameters on cell performance. Conclusions could be helpful for the experiments.
Resulting from simulations, high Peclet number decreases the thickness of the concentration boundary layer, current density could be increased. In detail, cathode transmission dominates whole performance where anode one works a little. Therefore, increasing oxidant concentration and diffusion coefficient elevates the cell performance quite well. A larger kinematic viscosity of the fuel also augments oxidant’s Peclet number to improve the performance. Geometrically, when flow rate is fixed, shrunk cross section area of the channel provides better performance for enlarged Peclet number. Altering aspect ratio of the cross section area to bring down area and bring up Peclet number shall be improving the cell performance greatly.

並列關鍵字

Membraneless ； Fuel Cells ； Peclet Number

參考文獻

Rosaria Ferringno, Abraham D. Strook, Thomas D. Clark, Michael Mayer, and George M. Whitesides, “Membraneless Vanadium Redox Fuel Cell Using Laminar Flow.” J. AM. CHEM. SOC. 124 (2002) 12930-12931.

Eric R. Choban, Larry J. Markoski, Andrzej Wieckowski, Paul J. A. Kenis, “Microfluidic fuel cell based on laminar flow.” J. Power Sources 128 (2004) 54-60.

Rustem F. Ismagilov, Abraham D. Stroock, Paul J. A. Kenis, and George M. Whitesides, “Experimental and theoretical scaling laws for transverse diffusive broadening in two-phase laminar flows in microchannels.” Appl. Phys. Lett. 76 (2000) 2376-2378.

M. A. Burns, B. N. Johnson, S. N. Brahmasandra, K. Handique, J. R. Webster, M. K. T. S. Sammarco, P. M. Man, D. Jones, D. Heldsinger, C. H. Mastrangelo, D. T. Burke, Science 282 (1998) 484-487.

K. Macounova, C. R. Cabrera, P. Yager, Anal. Chem. 73 (2001) 1627-1633.