Numerical Study of Liquid Water Saturation inside Gas Diffusion Layer and Micro Porous Layer during PEMFC Operations Using Multiscale and Multiphase Modeling Approach

2018 ◽  
Keyword(s):  
Porous Layer ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Water Saturation ◽  
Numerical Study ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Modeling Approach ◽  
Multiphase Modeling

Effect of the Micro-Porous Layer-Gas Diffusion Layer Interface on Water Transport in Polymer Electrolyte Fuel Cells

2009 ◽  
Author(s):  
Joshua Preston ◽  
Richard Fu ◽  
Xiaoyu Zhang ◽  
Ugur Pasaogullari
Keyword(s):  
Polymer Electrolyte ◽  
Cross Section ◽  
Porous Layer ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Water Saturation ◽  
Numerical Models ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Diffusion Media

An investigation of the liquid water saturation across the cross-section of an operating polymer electrolyte fuel cell is performed to analyze the saturation discontinuity predicted by numerical models. Numerical models have predicted a discontinuity in the liquid water saturation at the interface of the micro-porous layer and the coarser macroporous region of the gas diffusion layer. High-resolution through plane neutron radiography is used to acquire the water content distribution across the thickness of the gas-diffusion layer and study the effects of the interface. The measured liquid water profiles indicate no obvious discontinuity in the liquid water saturation across the cross-section of the bi-layer gas diffusion layer when large areas are averaged spatially. Evidence of the discontinuity is found when small spatial averaging is used in certain locations. Other locations show no evidence of the discontinuity. Scanning electron microscopy is used to examine the microstructure of two types of the bi-layer diffusion media. The images show that the approximation of the interface as a sudden, distinct feature may not be appropriate. The results suggest that a model that considers the existence of an interfacial region in the diffusion media may be appropriate, in which the properties vary continuously.

Effect of porosity gradient in cathode gas diffusion layer of polymer electrolyte membrane fuel cells on the liquid water transport using lattice Boltzmann method

2020 ◽  
pp. 095765092093431
Author(s):  
Mohammad Habiballahi ◽  
Hasan Hassanzadeh ◽  
Mohammad Rahnama ◽  
Seyed Ali Mirbozorgi ◽  
Ebrahim Jahanshahi Javaran
Keyword(s):  
Porous Media ◽  
Water Transport ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Water Saturation ◽  
Polymer Electrolyte Membrane ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Electrolyte Membrane ◽  
Liquid Water Transport

In this paper, a two-dimensional model has been developed to simulate the liquid water transport in a cathode gas diffusion layer with different porosity gradients in polymer electrolyte membrane fuel cells (PEMFCs). Due to the complexity of porous media, the simulation was carried out by lattice Boltzmann method. According to dimensionless numbers that characterize liquid water transport in porous media, simulation conditions were similar to the liquid water transfer into the gas diffusion layer of PEMFC. Different gas diffusion layers were created randomly by solid circular particles with an average diameter of [Formula: see text] and the numerical code was validated by conducting several tests. The results indicated that capillary force is the main factor in liquid water transport in the gas diffusion layer, while viscous and gravitational forces do not have a significant effect. In addition to improve the water management, the gas diffusion layer should have a positive porosity gradient, i.e. the porosity increases along the thickness. Also, under the same boundary conditions and at the average porosity (0.659), the saturation distribution curves in three porous media were compared including the gas diffusion layer with porosity gradient, the gas diffusion layer with the micro-porous layer, and the gas diffusion layer with uniform porosity. The average liquid water saturation in the gas diffusion layer with the 10% porosity gradient was 20.2% lower than in the gas diffusion layer with uniform porosity and 10.5% lower than the gas diffusion layer + micro-porous layer. Furthermore, upon elevation of the porosity gradient in the gas diffusion layer, the average liquid water saturation in the gas diffusion layer decreased. Specifically, as the porosity gradient rose from 10% to 14% and 18.5%, the average liquid water saturation values decreased to 29.8% and 38.8%, respectively compared with the gas diffusion layer with uniform porosity.

PEM Fuel Cell Gas Diffusion Layer Modelling of Pore Structure and Predicted Liquid Water Saturation

2011 ◽  
Author(s):  
J. Hinebaugh ◽  
A. Bazylak
Keyword(s):  
Fuel Cell ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Water Saturation ◽  
Pore Space ◽  
Three Dimensional ◽  
Gas Diffusion Layer ◽  
Gas Diffusion ◽  
Pore Network Model ◽  
High Porosity

An unstructured, three-dimensional pore network model is employed to describe the effect of through-plane porosity profiles on liquid water saturation within the gas diffusion layer (GDL) of the polymer electrolyte membrane fuel cell. Random fibre placements are based on the porosity profiles of six commercially available GDL materials recently obtained through x-ray computed tomography experiments. The pore space is characterized with a maximal ball algorithm, and invasion percolation-based simulations are performed. It is shown that water tends to accumulate in regions of relatively high porosity due to the lower associated capillary pressures. It is predicted that GDLs tailored to have smooth porosity profiles will have fewer pockets of high saturation levels within the bulk of the material. The results provide a more detailed picture of the possible water distributions in GDLs during operation.

Effect of Porosity Gradient in Gas Diffusion Layer on Cell Performance With Thin-Film Agglomerate Model in Cathode Catalyst Layer of a PEM Fuel Cell

2011 ◽  
Author(s):  
Chun-I Lee ◽  
Shiqah-Ping Jung ◽  
Kan-Lin Hsueh ◽  
Chi-Chang Chen ◽  
Wen-Chen Chang
Keyword(s):  
Thin Film ◽  
Fuel Cell ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Water Saturation ◽  
Catalyst Layer ◽  
Gas Diffusion Layer ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Water Flooding

A one-dimensional, steady-state, two-phase, isothermal numerical simulations were performed to investigate the effect on cell performance of a PEM fuel cell under non-uniform porosity of gas diffusion layer. In the simulation, the non-uniform porosity of gas diffusion layer was taken into account to analyze the transport phenomena of water flooding and mass transport in the gas diffusion layer. The porosity of the gas diffusion layer is treated as a linear function. Furthermore, the structure of the catalyst layer is considered to be a cylindrical thin-film agglomerate. Regarding the distribution analysis of liquid water saturation, oxygen concentration and water concentration depend on the porosity of gas diffusion layer. In the simulation, the εCG and εGC represent the porosity of the interfaces between the channel and gas diffusion layer and the gas diffusion layer and the catalyst layer, respectively. The simulation results indicate that when the (εCG, εGC) = (0.8, 0.4), higher liquid water saturation appears in the gas diffusion layer and the catalyst layer. On the contrary, when the (εCG, εGC) = (0.4, 0.4), lower liquid water saturation appears. Once the liquid water produced by the electrochemical reaction and condensate of vapor water may accumulate in the open pores of the gas diffusion layer and reduced the oxygen transport to the catalyst sites. This research attempts to use a thin-film agglomerate model, which analyze the significant transport phenomena of water flooding and mass transport under linear porosity gradient of gas diffusion layer in the cathode of a PEM fuel cell.

Pore Network Modeling of Oxygen Diffusion in Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells

2009 ◽  
Author(s):  
R. Wu ◽  
X. Zhu ◽  
Q. Liao ◽  
H. Wang ◽  
Y. D. Ding
Keyword(s):  
Diffusion Layer ◽  
Liquid Water ◽  
Oxygen Diffusion ◽  
Water Saturation ◽  
Effective Diffusivity ◽  
Gas Diffusion Layer ◽  
Pore Network ◽  
Gas Diffusion ◽  
Shielding Effect ◽  
Water Permeation

In the present study, a three dimensional pore network, consisting of spherical pores and cylindrical throats, is developed to simulate the oxygen diffusion and liquid water permeation in gas diffusion layer (GDL) in low-temperature fuel cell. Oxygen transport in the throats is described by Fick’s law and liquid water permeation in the network is simulated using percolation invasion algorithm. The effects of heterogeneity of GDL, connectivity of pores, and liquid water saturation on oxygen effective diffusivity are investigated respectively. The simulation results show that the GDL structure has a significant influence on the oxygen and water transport in the GDL. The oxygen effective diffusivity increases with increasing pore connectivity and decreasing heterogeneity. The shielding effect of large throats by smaller ones enhances with increasing heterogeneity of the network. Furthermore, the oxygen transportation is blocked in the presence of liquid water permeation. Thus the oxygen effective diffusivity drops significantly with increasing water saturation.

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