Existence of the phase drainage diagram in proton exchange membrane fuel cell fibrous diffusion media

Médici, Ezequiel; Allen, Jeffrey S.

doi:10.1016/j.jpowsour.2009.02.050

Cited by 50 publications

(56 citation statements)

References 22 publications

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“…24 In this fashion, the true Ca within the GDL may be somewhat different due to flow and spreading within the GDL. System pressure was measured without the GDL so that the differential breakthrough pressure could be isolated.…”

Section: Methodsmentioning

confidence: 99%

Liquid-Water Interactions with Gas-Diffusion-Layer Surfaces

Santamaria

Das

MacDonald

et al. 2014

J. Electrochem. Soc.

114

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Understanding dynamic liquid-water uptake and removal in gas-diffusion layers (GDLs) is essential to improve the performance of polymer-electrolyte fuel cells and related electrochemical technologies. In this work, GDL properties such as breakthrough pressure, droplet adhesion force, and detachment velocity are measured experimentally for commonly used GDLs under a host of test conditions. Specifically, the effects of GDL hydrophobic (PTFE) content, thickness, and water-injection area and rate were studied to identify trends that may be beneficial to the design of liquid-water management strategies and next-generation GDL materials. The results conclude that liquid water moving transversely through or forming at the surface of GDL may be affected by internal capillary structure. Adhesion-force measurements using a bottom-injection method were found to be sensitive to PTFE loading, GDL thickness, and injection area/rate, the latter of which is critical for defining the control-volume limits for modeling and analysis. It was observed that higher PTFE loadings, increased thickness, and smaller injection areas led to elevated breakthrough pressure; meaning there was a greater resistance to forming droplets. The data are used to predict the onset of droplet instability via a simple force-balance model with general trend agreement. Polymer-electrolyte fuel-cell (PEFC) and redox flow-battery (RFB) systems have the potential to improve energy efficiency and storage capabilities for mobile and grid-level applications in the near future. In PEFCs, the electrode structure is composed of a catalytic layer supported by porous gas-diffusion layers (GDLs) where multiphase reactant/product transport and electron conduction occur. Product liquid water can contribute to performance and degradation issues if not properly handled. Numerous studies have shown the importance of water-management strategies during start-up/shutdown and cooler operation where lower cell temperatures may lead to liquid buildup. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] In RFBs, GDLs serve a similar purpose of effective reactant distribution, especially for gaseous cells, 16,17 as well as serving as possible catalysts.18 Understanding multiphase, dynamic GDL water uptake and removal is essential to develop effective liquid-water management schemes as well as next-generation GDL materials for improved PEFC and RFB performance, stability, and component lifetimes.The influence of the porous-electrode structure on liquid/gas transport and PEFC performance has been studied by several groups focusing on the role of GDL and microporous layer (MPL) effects. [19][20][21][22] Capillary and viscous forces govern two-phase flow through GDLs; the dimensionless parameters that quantify them are the capillary number and viscosity ratio defined asandrespectively, where u is the superficial velocity of the non-wetting phase, γ is the surface tension, and μ is the wetting (wet) and nonwetting (nw) phase viscosities. 10,23 Under normal PEFC operation, capillary fo...

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Section: Methodsmentioning

confidence: 99%

Liquid-Water Interactions with Gas-Diffusion-Layer Surfaces

Santamaria

Das

MacDonald

et al. 2014

J. Electrochem. Soc.

114

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“…The three patterns, shown in Figure 3.3.27, are viscous fingering, capillary fingering, and stable displacement [140]. In a PEM fuel cell under normal operating conditions water will percolate through the GDL in a capillary fingering mode.…”

Section: Characterization Of Gdl Transport Properties -Capillary Fmentioning

confidence: 99%

“…The percolation pressure also presents unique characteristics depending on the flow pattern. This research was published in the Journal of Power Sources titled "Existence of the phase drainage diagram in proton exchange membrane fuel cell fibrous diffusion media" [140].…”

Section: Characterization Of Gdl Transport Properties -Capillary Fmentioning

confidence: 99%

“…When water is injected at a low constant rate (thus negligible viscous forces), the displacement will be dominated by capillary forces. Notably, at normal fuel cell operating conditions, the capillary number ( , in the range of 10 -8 -10 -5 , where u,  nw and  are the velocity, viscosity and surface tension respectively of non-wetting fluid) and viscosity ratio ( , 17.5) produce capillary-driven water flow [79,80]. One of the critical constitutive relationships for describing capillary flow in a porous material is capillary pressure versus liquid water saturation (P c vs. S w ).…”

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confidence: 99%

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Visualization of Fuel Cell Water Transport and Performance Characterization under Freezing Conditions

Kandlikar

Rao

et al. 2010

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“…There have been a few previous studies that have examined the resistance to lateral flow [38][39][40]. However, as we will report in this paper it can be ambiguous as to whether the water flow is through the GDL or between the GDLgasket interfaces.…”

Section: Introductionmentioning

confidence: 88%

Water Flow in, Through, and Around the Gas Diffusion Layer

et al. 2012

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Liquid water produced in polymer electrolyte membrane fuel cells is transported from the cathode catalyst/membrane interface through the gas diffusion layer (GDL) to the gas flow channel. Liquid water travels both laterally (in the plane of GDL) and transversely through the largest pores of the porous GDL structure. Narrow apertures in the largest pores are the primary resistance to liquid water penetration. Carbon paper has limiting apertures ∼20 μm in diameter and ∼1 μm in length whereas carbon cloth has apertures ∼100 μm in diameter and ∼200 μm in length. After sufficient hydrostatic pressure is applied, water penetrates the limiting aperture and flows through the pore. The pressure required for water to flow through the pores is less than the pressure to penetrate the limiting aperture of the pores. Water moved laterally and directed through a small number of transverse pores. There is less resistance to lateral liquid water flow at the interface between the GDL and a solid surface than through the GDL. The results from these experiments suggest that water flow through the GDL is dominated by a small number of pores and most pores remain free of liquid water.

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Existence of the phase drainage diagram in proton exchange membrane fuel cell fibrous diffusion media

Cited by 50 publications

References 22 publications

Liquid-Water Interactions with Gas-Diffusion-Layer Surfaces

Liquid-Water Interactions with Gas-Diffusion-Layer Surfaces

Visualization of Fuel Cell Water Transport and Performance Characterization under Freezing Conditions

Water Flow in, Through, and Around the Gas Diffusion Layer

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