Comparison of Water Thickness Profiles of Compressed PEMFC GDLs

2011 ◽  
Author(s):  
Pradyumna Challa ◽  
James Hinebaugh ◽  
A. Bazylak
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Water Distribution ◽  
Polymer Electrolyte Membrane ◽  
Water Injection ◽  
Liquid Water Content ◽  
Gas Diffusion ◽  
Injection Rate ◽  
Water Levels ◽  
Ex Situ

In this paper, through-plane liquid water distribution is analyzed for two polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs). The experiments were conducted in an ex situ flow field apparatus with 1 mm square channels at two distinct flow rates to mimic water production rates of 0.2 and 1.5 A/cm2 in a PEMFC. Synchrotron radiography, which involves high intensity monochromatic X-ray beams, was used to obtain images with a spatial and temporal resolution of 20–25 μm and 0.9 s, respectively. Freudenberg H2315 I6 exhibited significantly higher amounts of water than Toray TGP-H-090 at the instance of breakthrough, where breakthrough describes the event in which liquid water reaches the flow fields. While Freudenberg H2315 I6 exhibited a significant overall decrease in liquid water content throughout the GDL shortly after breakthrough, Toray TGP-H-090 appeared to retain breakthrough water-levels post-breakthrough. It was also observed that the amount of liquid water content in Toray TGP-H-090 (10%.wt PTFE) decreased significantly when the liquid water injection rate increased from 1 μL/min to 8 μL/min.

Investigation of Liquid Water Content of a Compressed PEMFC GDL Using Micro-Computed Tomography

2012 ◽  
Author(s):  
Ronnie Yip ◽  
Aimy Bazylak
Keyword(s):  
Computed Tomography ◽  
Water Content ◽  
Liquid Water ◽  
Water Injection ◽  
Three Dimensional ◽  
Liquid Water Content ◽  
Gas Diffusion ◽  
Ex Situ ◽  
Micro Ct ◽  
Micro Computed Tomography

With the current lack of understanding of the water transport phenomenon in the porous gas diffusion layers (GDLs) of the polymer electrolyte membrane fuel cells (PEMFCs), GDL designs are primarily implemented on a costly trial-and-error basis. In this work, an ex-situ device, suitable for micro-computed tomography (micro-CT) imaging, was designed to facilitate liquid water invasion of a GDL sample under flow field compression. The millimeter-scale apparatus allows for water injection from a point source with an opening diameter of 0.8 mm. A sample of felt-based Freudenberg GDL (H2315) was examined for the current study. Using micro-CT, the sample was scanned, before and after water invasion, to obtain high resolution, three-dimensional reconstructions of the dry GDL microstructures, as well as the liquid water patterns after breakthrough. These results were used to find the effect of liquid water content on the effective through-plane porosity for the felt-based Freudenberg GDL.

Proton transport resistance correlated to liquid water content of gas diffusion layers

2012 ◽  
Vol 209 ◽  
pp. 147-151 ◽  
Author(s):  
Jon P. Owejan ◽  
Jeffrey J. Gagliardo ◽  
Robert C. Reid ◽  
Thomas A. Trabold
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Proton Transport ◽  
Liquid Water Content ◽  
Gas Diffusion ◽  
Gas Diffusion Layers ◽  
Diffusion Layers

Effect of Liquid Water Saturation on Oxygen Transport in Gas Diffusion Layers of Polymer Electrolyte Fuel Cells

2010 ◽  
Author(s):  
Takeshi Shiomi ◽  
Richard S. Fu ◽  
Ugur Pasaogullari ◽  
Yuichiro Tabuchi ◽  
Shinichi Miyazaki ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Water Content ◽  
Polymer Electrolyte ◽  
Liquid Water ◽  
Water Saturation ◽  
Liquid Water Content ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cells ◽  
Oxygen Diffusivity ◽  
Liquid Saturation

Improved oxygen diffusivity is essential for reducing mass transport losses in polymer electrolyte fuel cells (PEFCs). In this work, effective oxygen diffusivity in the presence of liquid water inside a gas diffusion layer (GDL) was investigated by means of coupled experimental and numerical analyses. In order to control the liquid water content inside the GDL, a temperature gradient method was developed. In a separate experiment liquid water content inside the GDL was measured by neutron radiography (NR) and analyzed by using a two-phase, non-isothermal numerical model. The model accurately reproduced the total liquid water content and was in qualitative agreement with the liquid saturation trend as obtained from the NR experiments, which was utilized to estimate the liquid saturation in the limiting current experiment. Based on the predicted liquid water profile, the dependence of effective oxygen diffusivity on the liquid water saturation is deduced. It is found that the Bruggeman exponent factor is much larger than the predictions from network models and this suggests that the understanding of the relationship between liquid water transport and the GDL local structure is important.

Measurement of Liquid Water Content Inside the Gas Diffusion Layer

2012 ◽  
Author(s):  
Siddiq Hussain Tahseen ◽  
Kehan Chen ◽  
Mehdi Shahraeeni ◽  
Samuel C. M. Yew ◽  
Mina Hoorfar
Keyword(s):  
Water Content ◽  
Capillary Pressure ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Gas Diffusion Layer ◽  
Liquid Water Content ◽  
Gas Diffusion ◽  
Water Volume ◽  
Significant Difference ◽  
The Impact

The amount of the liquid water present at the gas diffusion layer (GDL) has an impact on the diffusivity, capillary pressure and the permeability which in turn influences convective and diffusive transport. A prodigious amount of research has been conducted to study and measure the different properties (time of breakthrough and capillary pressure versus saturation) associated with the breakthrough condition. However, most of the reported data ignored the impact of expansion of different components in the set-up (such as tubing) and the condition after the time of breakthrough. The focus of this study is to measure the breakthrough pressure and time of breakthrough and hence determine the liquid water content inside the GDL before the time of breakthrough. The measurements are performed for different samples to study the effect of the thickness and hydrophobic contents. The results show that expansion has significant difference in the determination of water volume inside the GDL.

Pore Network Modeling to Study the Effects of Common Assumptions in GDL Liquid Water Invasion Studies

2012 ◽  
Author(s):  
J. Hinebaugh ◽  
A. Bazylak
Keyword(s):  
Liquid Water ◽  
Polymer Electrolyte Membrane ◽  
Three Dimensional ◽  
Pem Fuel Cells ◽  
Pore Network ◽  
Gas Diffusion ◽  
Ex Situ ◽  
Network Modelling ◽  
Electrolyte Membrane ◽  
Inlet Conditions

Topologically equivalent pore network modelling of polymer electrolyte membrane (PEM) fuel cell gas diffusion layer (GDL) materials was employed to simulate ex-situ liquid water invasion experiments commonly conducted to investigate multiphase transport in PEM fuel cells. Stochastic, three dimensional pore spaces are numerically reconstructed to mimic carbon fibre paper based GDL materials. A watershed based method was used for extracting pore networks from a range of sample sizes. Invasion percolation was employed to simulate liquid water originating at one surface of the material and percolating through to the opposite surface. Inlet reservoir areas were chosen to mimic those used in ex-situ experiments in literature. It was found that sample size has a strong overall effect on saturation levels and inlet conditions primarily affected saturation near the inlet.

Elucidating Liquid Water Distribution and Removal in an Operating Proton Exchange Membrane Fuel Cell via Neutron Radiography

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Michael A. Hickner ◽  
Ken S. Chen ◽  
Nathan P. Siegel
Keyword(s):  
Flow Velocity ◽  
Water Content ◽  
Liquid Water ◽  
Water Distribution ◽  
Gas Flow ◽  
Proton Exchange Membrane ◽  
Neutron Radiography ◽  
Liquid Water Content ◽  
Proton Exchange ◽  
Gas Flow Velocity

Neutron radiography was used to quantify the steady-state water content and its distribution in a 50 cm2 operating proton exchange membrane fuel cell. It was observed that the liquid water distribution near the corners of the gas-flow channels (GFCs) is influenced by the local gas-flow velocity as determined by the cathode stoichiometric flow ratio. At low velocity, the distribution of liquid water down the channel was found to be fairly uniform with only a slight reduction in liquid water content at the exit of the GFC corners. It was further observed that as the cathode gas-flow velocity is increased, a noticeable pattern develops in which liquid water is concentrated at the entrance to the GFC corners and becomes depleted in the corner and near the exit of the corner; liquid water content again increases further down the channel away from the corners. A single-phase computational fluid dynamics (CFD) model was developed and employed to help explain the observed water-distribution patterns. Flow-fields computed from our CFD model reveal recirculation regions in the GFC corners as well as in the areas of increased local gas-flow velocity, which help explain the experimentally observed liquid water distribution.

scholarly journals Liquid-water content and water distribution of wet snow using electrical monitoring

2020 ◽  
Author(s):  
Pirmin Philipp Ebner ◽  
Aaron Coulin ◽  
Joël Borner ◽  
Fabian Wolfsperger ◽  
Michael Hohl ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Water Content ◽  
Liquid Water ◽  
Water Distribution ◽  
Liquid Water Content ◽  
Heating Process ◽  
Snow Sample ◽  
Starting Point ◽  
Water Percolation ◽  
Wet Snow

Abstract. Snow exists in a wide range of temperatures and around its melting point snow becomes a three-phase material. A better understanding of wet snow and the first starting point of water percolation in the seasonal snowpack is essential for snow pack stability, snow melt run-off and remote sensing. In order to induce and measure precisely the liquid water and the corresponding dielectric properties inside a snow sample, an experimental setup was developed. Using microwave heating at 18 kHz allows the use of dielectric properties of ice to enable heat to be dissipated homogeneously through the entire volume of snow. A desired liquid water content inside the snow sample could then be created and analysed in a micro-computer tomography. Based on the electrical monitoring a promising perspective for retrieving water content and water distribution in the snowpack is given. The heating process and extraction of water content are mainly dependent on the morphological properties of snow, the temperature and the liquid water content. The experimental observation can be divided in three different heating processes affecting the dielectric properties of snow for different densities: (1) dry snow heating process up to 0 °C indicating a temperature and snow structure dependency of the dielectric property of snow; (2) wet snow heating at stagnating temperature of 0 °C and the presence of uniformed distributed liquid water changes the dielectric properties. The presence of liquid water decreases the impedance of the snow sample until water starts to percolate; and (3) the start of water percolation is between 5–12 water volume fraction depending on the snow density and confirms the literature findings. The onset of water percolation initiated an inhomogeneity in snow and water distribution, strongly affecting the dielectric properties of the snow. These findings are pertinent to the interpretation of the snow melt run-off of spring snow. These laboratory measurements allow to find the narrow range of the starting point of water percolation in coarse-grained snow and to extract the corresponding dielectric properties which is important for remote sensing.

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