微型質子交換膜燃料電池流道深度對電池性能的影響

The Effects of Channel Depth on the Performance of Miniature Proton Exchange Membrane Fuel Cells

林煥剛(Huan-Gang Lin)

指導教授 ： 張迪惠

朝陽科技大學/理工學院/環境工程與管理系/碩士(2015年)

摘要

質子交換膜燃料電池雙極板中的流道形式與幾何尺寸是影響燃料電池性能的重要關鍵，因為燃料藉由流道輸送，並提供給觸媒層經由電化學作用產生電能，而流道之間的肋用來引導電流提供外部使用。在燃料電池的開發過程中，常以電腦模擬的方式來找尋其相關的操作變數與流道設計，或藉由模擬數據來解釋實際電池所呈現的結果。
然而在過去有關流道設計的文獻中，卻很少有針對微型燃料電池的流道深度所進行的研究，原因是微型燃料電池的高深寬比的流道加工不易，模擬無法得到適當的驗證。本研究分別以蛇形流道和類蛇形流道進行模擬與單一電池實驗分析。由於微型燃料電池對反應面積的限制，本研究採用流道寬與肋寬皆為0.5 mm於20mm×20mm的反應面積上，分析三種不同的流道深度0.3、0.4、0.6 mm 對電池性能所造成得影響。本研究利用有限元素分析軟體COMSOLMultiphysics 4.4建立燃料電池三維模組來進行模擬分析與求解，再利用微放電加工製作微型SUS316L雙極板，並組裝為單一電池後進行驗證。
透過電池性能極化曲線來比較模擬與實驗結果，結果顯示相當吻合。在流道深度為0.3, 0.4, and 0.6 mm時，蛇形流道的最大尖端功率密度分別約為500、580、530 mW/cm2，而類蛇形流道則分別約為395、530、510 mW/cm2。無論蛇形與類蛇形流場，流道深度為0.4 mm可產生較佳的性能，其中蛇形蛇形流場深度為0.4 mm時可產生約580 mW/cm2的功率密度，為各流道與深度中最佳者。蛇形流場性能比類蛇形流場更加有利。在兩種流道形式中，當流道太淺時，陰極流速分布極不均勻，其內側流道流速甚至趨近於零，影響燃料輸送與排水效率，進而降低電池性能。流道越深越能形成穩定的渦流，較有可能形成高排水效率的環狀流。但流道太深時，由於流速減少，造成燃料的擴散效率減少，而稍微降低電池性能。

關鍵字

燃料電池 ； MEA ； 質子交換膜 ； 流道深度

並列摘要

The geometric parameters and flow patterns of flow channels strongly influence the performance of PEMFCs. It is through the flow channels that the fuel is transported to the catalyst layer where electrochemical reaction occurs, generating electricity. The rib then delivers electric current,providingelectric power for outer circuit. Computer simulation is usually applied in fuel cells to obtain suitable operation parameters and optimize flow channel design. It can also interpret the laboratory results ofcell test.
In the literature,very few researcheshave been focused on the impact of channel depth on the miniature fuel cells. This is because the fabrication of miniature bipolar plates with high channel depth-to-width aspect ratio is a big challenge. Validation of simulation results is not possible without laboratory results. In this study, the performances both serpentine and serpentine-like flow fields are evaluated based on simulation and single cell test. Due to the restriction in the active area of miniature fuel cells, both channel and rib width in this study were set to be 0.5 mm in an active area of 20mm×20mm. The performances of fuel cell were evaluated and compared based on three different channel depths--0.3, 0.4, and 0.6 mm. A three-dimensional model for a PEMFC has been approached and implemented for its solution based on finite elemental method software, COMSOL Multiphysics 4.4. Die-sinking micro-electrical discharge machining was applied to fabricate miniature SUS316L bipolar plates, which were then assembled to a single cell for validating simulation results.
Based on the polarization curves, the simulation results generally agree with experimental data. With the channel depths of 0.3, 0.4, and 0.6 mm, respectively, the peak power densities of serpentine flow fields are 500, 580, and 530 mW/cm2, while those of serpentine-like flow fields are 395, 530, and 510 mW/cm2. At a channel depth of 0.4 mm, both flow fields produce their highest power densities compared with those at other depths. The serpentine flow fields with a channel depth of 0.4 mm produce the highest power density of 580 mWcm-2.The cell performance of serpentine flow fieldsis generally more favorable than that of serpentine-like flow fields.For both flow fieldswith shallower channel depths, the distribution of flow velocity in cathode channel is significantly heterogeneous. The velocities in the paths of inner loops even approach to zero, which affects the fuel delivery and water removal, consequently reducing the cell performance.Deeper flow channels generally create vortex flow, which is more likely to form annular flow with high efficiency in water removal. However, the cell performance decreases with too deep channel depth, because the efficiency of fueldiffusion decreases with lower flow velocity.

並列關鍵字

Fuel cells ； MEA ； PEMFCs ； Channel Depth

參考文獻

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