Imaging of the desaturation of gas diffusion layers by synchrotron computed tomography

Battrell, Logan; Patel, Virat; Zhu, Ning; Zhang, Lifeng; Anderson, Ryan

doi:10.1016/j.jpowsour.2019.01.089

Cited by 8 publications

(6 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The experiments were designed to emulate evaporative water removal from a saturated catalyst layer through the GDL into a gas channel and investigate the effects of temperature, gas flow, and evaporation domain size on the evaporation rates. An ex situ cell design [11,34] (Figure 1a) was chosen to assure controllability of the boundary conditions and compatibility with X-ray tomographic microscopy (XTM), which is commonly used to determine the distribution of water inside fuel cell GDLs [22,23,[34][35][36][37][38][39]. The configuration of water and GDL during the evaporation measurement can be seen in the XTM images in Figure 1b.…”

Section: Methodsmentioning

confidence: 99%

“…The artificial distribution of hydrophobic and hydrophilic GDL domains enables tailormade patterns of water filled lines with high levels of evaporation rates and necessitates a good understanding of the vapor removal mechanisms, ultimately limiting the rate of evaporation. Understanding the characteristic mechanisms and limitations to evaporative water removal in the framework of PEFCs and quantifying them has been the aim of many scientific works, both experimentally [21][22][23][24][25] and numerically [26][27][28][29][30][31][32]. However, the reported evaporation values show a wide spread [31,33] and some measurements performed on differential cell scales leave open questions of how evaporative flux scales with GDL thickness and gas type are used in the evaporation rate measurements, as reported by Lal et al [21].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mass Transport Limitations of Water Evaporation in Polymer Electrolyte Fuel Cell Gas Diffusion Layers

et al. 2021

View full text Add to dashboard Cite

Facilitating the proper handling of water is one of the main challenges to overcome when trying to improve fuel cell performance. Specifically, enhanced removal of liquid water from the porous gas diffusion layers (GDLs) holds a lot of potential, but has proven to be non-trivial. A main contributor to this removal process is the gaseous transport of water following evaporation inside the GDL or catalyst layer domain. Vapor transport is desired over liquid removal, as the liquid water takes up pore space otherwise available for reactant gas supply to the catalytically active sites and opens up the possibility to remove the waste heat of the cell by evaporative cooling concepts. To better understand evaporative water removal from fuel cells and facilitate the evaporative cooling concept developed at the Paul Scherrer Institute, the effect of gas speed (0.5–10 m/s), temperature (30–60 °C), and evaporation domain (0.8–10 mm) on the evaporation rate of water from a GDL (TGP-H-120, 10 wt% PTFE) has been investigated using an ex situ approach, combined with X-ray tomographic microscopy. An along-the-channel model showed good agreement with the measured values and was used to extrapolate the differential approach to larger domains and to investigate parameter variations that were not covered experimentally.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mass Transport Limitations of Water Evaporation in Polymer Electrolyte Fuel Cell Gas Diffusion Layers

et al. 2021

View full text Add to dashboard Cite

show abstract

“…In this study, we investigate the mechanisms of water accumulation to improve water management strategies in fuel cells. This understanding is facilitated by imaging techniques sensitive to water such as neutron − and X-ray imaging. − X-ray tomographic microscopy (XTM) specifically has shown great promise in small-scale studies focusing on interactions between the water and the GDL structure in the micrometer range and with increasingly higher temporal resolution. Recent developments in synchrotron-based XTM at the TOMCAT beamline of the Swiss Light Source (SLS) enable the observation of time-resolved (subsecond time resolution), dynamic processes in 3D occurring during cluster formation in operando fuel cells, while still maintaining a spatial resolution in the micrometer range. , …”

Section: Introductionmentioning

confidence: 99%

Operando Liquid Pressure Determination in Polymer Electrolyte Fuel Cells

Mularczyk

Lin

Niblett

et al. 2021

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

Extending the operating range of fuel cells to higher current densities is limited by the ability of the cell to remove the water produced by the electrochemical reaction, avoiding flooding of the gas diffusion layers. It is therefore of great interest to understand the complex and dynamic mechanisms of water cluster formation in an operando fuel cell setting as this can elucidate necessary changes to the gas diffusion layer properties with the goal of minimizing the number, size, and instability of the water clusters formed. In this study, we investigate the cluster formation process using X-ray tomographic microscopy at 1 Hz frequency combined with interfacial curvature analysis and volume-of-fluid simulations to assess the pressure evolution in the water phase. This made it possible to observe the increase in capillary pressure when the advancing water front had to overcome a throat between two neighboring pores and the nuanced interactions of volume and pressure evolution during the droplet formation and its feeding path instability. A 2 kPa higher breakthrough pressure compared to static ex situ capillary pressure versus saturation evaluations was observed, which suggests a rethinking of the dynamic liquid water invasion process in polymer electrolyte fuel cell gas diffusion layers.

show abstract

“…For dynamic water transfer processes, Zenyuk et al, (2016) visualized the water evaporation in several GDLs with gas flow rates of 200 and 600 ml/min at 30°C. The desaturation process in the GDL was also visualized by Battrell et al (Battrell et al, 2018;Battrell et al, 2019) for both global and localized GDL areas, with the gas flow rate at 50 ml/min.…”

Section: Introductionmentioning

confidence: 99%

“…Spernjak et al (Spernjak et al, 2007;Spernjak et al, 2010) experimentally investigated the liquid water formation and transport in a single-serpentine PEM fuel cell, and also compared the liquid water dynamics in parallel, serpentine, and interdigitated flow fields using neutron imaging and digital camera. Battrell et al (2019) quantitatively visualized the water removal in the GDL with serpentine gas channels, considering the effects of flow field geometry. Ding et al (2020) compared the cell performances of a parallel, interdigitated, and serpentine flow field with normal and wavelike channels using a three-dimensional, two-phase, non-isothermal model.…”

Section: Introductionmentioning

confidence: 99%

Visualizing Water Desaturation in Frozen Gas Diffusion Layers With Flow Field Segmentation via Synchrotron X-Ray Radiography

et al. 2021

Self Cite

View full text Add to dashboard Cite

Synchrotron X-ray tomography images were used to study dynamic, regional water transfer behavior in the gas diffusion layer (GDL) during thawing and desaturation processes. Initially saturated, frozen GDLs were thawed and desaturated with air in a serpentine gas flow channel. On-the-fly (OTF) high speed CT scans via synchrotron X-ray allowed the capture of consecutive water transfer inside the GDL under the cold start-up gas purging condition. Desaturation data of Sigracet 35AA GDLs with three superficial gas velocities (2.88–5.98 m/s) were selected for analysis. Multiple spatial segmentation levels based on the flow field geometry, including channel vs. rib, individual channels and ribs, and smaller sections in each channel and rib, were applied to the in-plane direction to study the GDL regional thawing and desaturation behaviors. Each segmentation volume had a similar desaturation pattern in general; however, water distribution and desaturation show heterogeneity over the GDL domain, as well as relation with factors including the flow field geometry, air traveling distance, and initial saturation level. These data from the segmentation analysis expand the knowledge of localized water transfer behavior during the cold start thawing process. These data can also provide valuable information for future cold start modeling and help in optimizing the PEM fuel cell flow field design.

show abstract

Imaging of the desaturation of gas diffusion layers by synchrotron computed tomography

Cited by 8 publications

References 37 publications

Mass Transport Limitations of Water Evaporation in Polymer Electrolyte Fuel Cell Gas Diffusion Layers

Mass Transport Limitations of Water Evaporation in Polymer Electrolyte Fuel Cell Gas Diffusion Layers

Operando Liquid Pressure Determination in Polymer Electrolyte Fuel Cells

Visualizing Water Desaturation in Frozen Gas Diffusion Layers With Flow Field Segmentation via Synchrotron X-Ray Radiography

Contact Info

Product

Resources

About