Effect of flow channel designs on the cell performance and the local transport phenomena of proton exchange membrane fuel cells

• Main Authors: Chun-Hao Huang, 黃俊豪
• Other Authors: Ruey-Yih Tsai
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/67569135306315525493

博士 === 中原大學 === 機械工程研究所 === 99 === Abstract The purpose of the thesis is to establish a three dimensional PEM fuel cell model. The main objective is to investigate the phenomena of the elector/mass transfer inside a proton exchange membrane fuel cell with flow fields design (parallel flow field, serpentine flow field, interdigitated flow field, Z-type interdigitated flow field, parallel-interdigitated mixed flow field and grid flow field). In addition, the effects of operation condition (fuel cell temperature, inlet humidification temperature, porosity of diffusion layer, permeability of diffusion layer, inlet flow pressure, inlet velocity and gaseous fuel flow direction) on the cell performance and flow channel pressure drop of the PEM fuel cells under the real operating conditions are examined in detail by different air flow rates. Add the condition of the effect of the wall heat transfer; observed the effect of heat distribution and performance of internal and external heat transfer for fuel cell. The simulation results show that the inlet humidification increase to 80oC and decreasing the cell temperature to 50oC while the flow direction is counter-flow provides the best cell performance. While in the higher gas diffusion layer porosity and permeability that can reduce mass transfer impedance and dead zone area, allows more fuel gas transport into the catalyst layer of cathode and participate in the electrochemical reaction, and improves the cell performance. The performance of PEM fuel cell can also significantly improved by increasing the pressure of the cathode flow channel by incorporating forced convection. As increasing the inlet velocity it can promoted oxygen content on the flow channel and improve the cell performance. The heat distribution is effected on fuel cell when the heat conduction coefficient changed. If the heat conduction coefficient is getting larger, the current density will increase too. If the heat convection coefficient is getting larger, the current density will increase too, and then affect the cooling rate. H2 crossover rate increases with increasing the cell temperature, gas diffusion layer porosity and permeability. The H2 crossover rate decreases with increasing the inlet humidification, due to the increase in membrane flexibility when inlet humidification was increased. A monotonic increase in the H2 crossover rate with increasing backpressure of the anode will result in a H2 partial pressure increase, which then creates a larger pressure difference across the PEM. For the effects of the main operating condition on the cell performance curve, local current density distribution, phenomena of the mass transfer, temperature distribution and flow channel pressure drop, although the interdigitated flow field have a slightly larger pressure drop than those with parallel flow field or parallel-interdigitated mixed flow field, but the cell performance is lower the serpentine flow field and Z-type interdigitated flow field. For this reason, the interdigitated flow field behaves with the economic benefits in practical application.