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Methanol, water and heat transport in direct methanol fuel cells for portable power.

机译：直接甲醇燃料电池中的甲醇，水和热能传输为便携式电源。

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摘要

Small-scale direct methanol fuel cells (DMFCs) are expected to be next generation power sources for portable applications. High performance of a portable DMFC is determined by the methanol, water and heat transport processes, as well as their complex interactions under a wide variety of operating conditions and design regimes. The present thesis aims to developing a theoretical understanding of these transport phenomena and hence their effects on electrochemical performance of the DMFC. Based on the latest experimental observations, two-phase mathematical models have been developed.; A one-dimensional (1D) model for the membrane-electrode-backing layer assembly in a DMFC is developed for the first time to predict not only polarization curves and methanol crossover but also water crossover and transient discharge behavior coupled with the temperature evolution in a portable DMFC. The model results show good agreement with experimental data of overall cell performance, methanol and water crossover rates through the membrane, as well as reveal a positive interactive feedback mechanism between the transient temperature and methanol crossover profiles, coupled by transient cell voltage and cell energy efficiency profiles, under varied operating conditions.; Next, a multi-dimensional (multi-D) model, making use of a multi-phase mixture (M2) formulation, is developed to encompass all components in the DMFC in a single computational domain. A commercial computational fluid dynamics (CFD) software package, FluentRTM, is employed to solve species transport and electrochemical equations simultaneously. The model results discover an interesting interplay between the local current density and methanol crossover rate distributions for the first time, indicating that the anode flow field design and methanol feeding concentration are two key parameters for the optimal cell performance. When considering electron transport and interfacial liquid coverage on the cathode backing surface, the predicted results provide further insight into the geometrical effect on current density distribution and water transport through the membrane. With an accurate interfacial coverage correlation, water balance between the anode and cathode can be potentially tailored to accommodate the use of high concentration of methanol as fuel, without sacrificing cell performance.; The future work of numerical modeling should involve more complete solutions including both steady state and transient state, and more efficient solutions using improved numerical algorithms. This future work is expected to have important impact on the further development of DMFC technology as portable power.
机译：小型直接甲醇燃料电池（DMFC）有望成为便携式应用的下一代电源。便携式DMFC的高性能取决于甲醇，水和热传输过程，以及它们在各种运行条件和设计方案下的复杂相互作用。本发明旨在发展对这些传输现象及其对DMFC的电化学性能的影响的理论理解。基于最新的实验观察，已经开发了两阶段数学模型。首次开发了DMFC中膜-电极-背衬层组件的一维（1D）模型，不仅可以预测极化曲线和甲醇交换，还可以预测水的交换和瞬态放电行为以及温度的变化。便携式DMFC。模型结果与整体电池性能，穿过膜的甲醇和水的交叉速率的实验数据显示出良好的一致性，并揭示了瞬态温度和甲醇跨接曲线之间的正交互反馈机制，以及瞬态电池电压和电池能量效率轮廓，在不同的操作条件下；接下来，开发了利用多相混合物（M2）公式的多维（multi-D）模型，以在单个计算域中包含DMFC中的所有组件。商业计算流体动力学（CFD）软件包FluentRTM用于同时求解物种迁移和电化学方程。该模型结果首次发现了局部电流密度与甲醇交换速率分布之间的有趣相互作用，这表明阳极流场设计和甲醇进料浓度是获得最佳电池性能的两个关键参数。当考虑到阴极背衬表面上的电子传输和界面液体覆盖时，预测的结果可进一步洞察电流密度分布和水通过膜的几何效应。通过精确的界面覆盖率相关性，可以潜在地调整阳极和阴极之间的水平衡，以适应使用高浓度的甲醇作为燃料，而不会牺牲电池性能。数值建模的未来工作应涉及更完整的解决方案，包括稳态和瞬态，以及使用改进的数值算法的更有效解决方案。预计未来的工作将对DMFC技术作为便携式电源的进一步发展产生重要影响。

著录项

  • 作者

    Liu, Wenpeng.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 202 p.
  • 总页数 202
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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