Modeling two-phase flow in three-dimensional complex flow-fields of proton exchange membrane fuel cells

Summary Fuel cell vehicles face complicated road conditions, which may impact on the output performance of fuel cell stacks. In the present study, the water transport in the gas diffusion layer (GDL) of proton exchange membrane fuel cell (PEMFC) under vibration conditions are investigated. A stochastic method is employed to reconstruct the 3‐D GDL with experimentally validated varying porosities. The volume of fluid (VOF) method is adopted to investigate the two‐phase problems. Sinusoidal vibration source terms are superposed, which can vary with required amplitudes and directions. Over time, the water transport process takes three steps: water intrusion, water accumulation, and water removal. The water intrusion tends to start from the sides of the GDL, then spreads into the central area. Compared with the no‐vibration case, the water saturations are higher in both the vertical and horizontal vibration cases. The vibration will enhance the water transport through GDL layers. As such, the higher the vibration amplitude and frequency, the larger the water saturation. Accordingly, the water saturation of the GDL vary sinusoidally over time. The water breakthrough paths are identified and compared during the water removal processes. Vibration in the horizontal direction is much easier to promote the water transport inside a layer compared with vibration in the vertical direction. More substantial water saturation in the GDL layers will restrict the gas transfer paths. Consequently, less oxygen will participate in the reaction, which will further impact on the fuel cell performance.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Water transport in the gas diffusion layer of proton exchange membrane fuel cell under vibration conditions

Jiao

Niu

et al. 2020

“…The baffles were installed in flow channels, and the flow behaviors and transfer behaviors of reactants were optimized. The reactant supplying to catalyst layers (CLs) could be enhanced, and the current density could be improved . Many baffles in different shapes had been studied by previous works, including the wave‐like baffles, trapezoidal baffles, and rectangular baffles.…”

Section: Introductionmentioning

confidence: 99%

“…Meanwhile, the local flow velocities around baffles could be increased; therefore, the convective heat transfer was enhanced. In trapezoidal baffled flow channels, the authors of these papers found that trapezoidal baffles could also improve the cell performances; meanwhile, the liquid water could be removed efficiently. However, when the baffles were used, the power loss accounted by the pumping power in reactant delivering process was also increased .…”

Section: Introductionmentioning

confidence: 99%

Mass transfer in proton exchange membrane fuel cells with baffled flow channels and a porous‐blocked baffled flow channel design

Chen

Guo

et al. 2019

Summary In proton exchange membrane fuel cells, baffled flow channels enhance the reactant transfer from flow channels to gas diffusion layers. However, the reactant transfer depends on both the diffusive transfer and convective transfer, and how the baffles in flow channels affect them is still unknown. Therefore, in this work, a two‐dimensional, two‐phase, nonisothermal, and steady‐state model of proton exchange membrane fuel cells is developed, and these two transfer processes from flow channels to gas diffusion layers are comparatively studied. Simulation results show that first of all, the reactant transfer from flow channels to gas diffusion layers mainly depends on the diffusive transfer. Therefore, if the desire is to enhance the mass transfer from flow channels to gas diffusion layers, the diffusive mass transfer should be enhanced firstly. Being guided by this goal, a porous‐blocked baffled flow channel is developed. This flow channel design can further enhance the reactant transfer from flow channels to gas diffusion layers, and the cell performance can be improved. Moreover, when the porosities of porous blocks at the front place of flow channels are lower, the cell power is also increased but the pumping power can be reduced a lot.

“…In the past decades, numbers of researchers studied the mass transfer and performance of PEMFCs with different flow fields, such as the parallel flow field, serpentine flow field, and interdigited flow field. They found that the flow field design significantly affected the heat and mass distribution and the output performance …”

Section: Introductionmentioning

confidence: 99%

Baffle shape effects on mass transfer and power loss of proton exchange membrane fuel cells with different baffled flow channels

Guo

Chen

et al. 2019

Summary In proton exchange membrane fuel cells, baffled flow channels can enhance the reactant transfer and improve the cell performance. Many different baffled flow channels have been numerically studied in previous published papers. However, what kind of baffled flow channels can improve the cell performance most is still unknown. In this simulation work, a two‐dimensional, two‐phase, nonisothermal, and steady‐state model of proton exchange membrane fuel cells is developed. The mass transfer and cell performance of PEMFCs with different baffled flow channels have been numerically compared. Simulation results show that the rectangular baffle can enhance the reactant transfer most and improve the cell performance most; however, the power loss in rectangular baffled flow channel is also the highest. To inherit the advantages and overcome the shortages of the rectangular baffled flow channel, an optimized baffled flow channel is developed. In this newly developed baffled flow channel, the windward side is designed as the streamline shape and the leeward side is designed as the sloped shape. Results of the simulation also show that the optimized baffled flow channel can reduce the power loss accounted by the pumping power in reactant delivering process and the cell performance can be further improved.