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<p>Bipolar plates are crucial components to overcome the challenges in the widespread commercialization of Proton Exchange Membrane Fuel cells (PEMFCs) through weight and cost reductions. Hence, graphite composite bipolar plates emerge as a preferable alternative to traditional metallic ones due to their lighter weight and lower cost. However, the effects of their channel sizing parameters on fluid flow, mass transfer, current distribution, and temperature distributions considering both anodic and cathodic flows of bipolar plates haven’t been thoroughly examined. Therefore, this work assessed the performance of a CNT-reinforced graphite composite bipolar plate channel design according to the r/w ratios by using multi-physical CFD (Computational Fluid Dynamics) simulation. According to the findings, when r/w ratios rise to 6.5, cell power density increases by 57.3% through enhancements in the cell mass transfer; after that, it declines by 6.35% until r/w ratio of 14 due to mass transfer limitations related to low diffusion of reactants and poor liquid water discharge capabilities. Additionally, in-depth anodic and cathodic flow characterizations according to the r/w ratios have revealed three types of mass transfer mechanisms: (1) a through-plane diffusion, (2) a through-plane and in-plane diffusions with flow mixing, and (3) a through-plane and in-plane diffusions without flow mixing, each resulting in distinct species distribution on the catalyst surfaces. The current density and temperature profiles also exhibited a strong dependence on the r/w ratio. Generally, it was discovered that the performance of CNT-reinforced graphite composite bipolar plate improves significantly within r/w ratios between 0.5 and 4. In this range, enhanced through-plane diffusions and the mixing nature of the under-rib flows facilitate the mass transfer of the reacting species, while the rib thickness remains sufficient to promote effective heat and current conduction within the cell, thereby enhancing overall cell performance.</p>

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Theoretical Investigations on the Effect of Rib Width-to-Channel Width Ratio of a CNT-Reinforced Graphite Composite Bipolar Plate on the Performance of PEMFCs

  • 期刊论文

  • 发表日期：

    2025年8月13日

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  • Dawit Musse Yasin,
  • Dongkyoung Lee

摘要

Bipolar plates are crucial components to overcome the challenges in the widespread commercialization of Proton Exchange Membrane Fuel cells (PEMFCs) through weight and cost reductions. Hence, graphite composite bipolar plates emerge as a preferable alternative to traditional metallic ones due to their lighter weight and lower cost. However, the effects of their channel sizing parameters on fluid flow, mass transfer, current distribution, and temperature distributions considering both anodic and cathodic flows of bipolar plates haven’t been thoroughly examined. Therefore, this work assessed the performance of a CNT-reinforced graphite composite bipolar plate channel design according to the r/w ratios by using multi-physical CFD (Computational Fluid Dynamics) simulation. According to the findings, when r/w ratios rise to 6.5, cell power density increases by 57.3% through enhancements in the cell mass transfer; after that, it declines by 6.35% until r/w ratio of 14 due to mass transfer limitations related to low diffusion of reactants and poor liquid water discharge capabilities. Additionally, in-depth anodic and cathodic flow characterizations according to the r/w ratios have revealed three types of mass transfer mechanisms: (1) a through-plane diffusion, (2) a through-plane and in-plane diffusions with flow mixing, and (3) a through-plane and in-plane diffusions without flow mixing, each resulting in distinct species distribution on the catalyst surfaces. The current density and temperature profiles also exhibited a strong dependence on the r/w ratio. Generally, it was discovered that the performance of CNT-reinforced graphite composite bipolar plate improves significantly within r/w ratios between 0.5 and 4. In this range, enhanced through-plane diffusions and the mixing nature of the under-rib flows facilitate the mass transfer of the reacting species, while the rib thickness remains sufficient to promote effective heat and current conduction within the cell, thereby enhancing overall cell performance.