Analysis of liquid water transport in fuel cell gas diffusion media using two-mobile phase pore network simulations

2011 ◽  
Vol 196 (5) ◽  
pp. 2725-2734 ◽  
Author(s):  
B. Markicevic ◽  
N. Djilali
Author(s):  
Luis Breziner ◽  
Peter Strahs ◽  
Parsaoran Hutapea

The objective of this research is to analyze the effects of vibration on the performance of hydrogen PEM fuel cells. It has been reported that if the liquid water transport across the gas diffusion layer (GDL) changes, so does the overall cell performance. Since many fuel cells operate under a vibrating environment –as in the case of automotive applications, this may influence the liquid water concentration across the GDL at different current densities, affecting the overall fuel cell performance. The problem was developed in two main steps. First, the basis for an analytical model was established using current models for water transport in porous media. Then, a series of experiments were carried, monitoring the performance of the fuel cell for different parameters of oscillation. For sinusoidal vibration at 10, 20 and 50Hz (2 g of magnitude), a decrease in the fuel cell performance by 2.2%, 1.1% and 1.3% was recorded when compared to operation at no vibration respectively. For 5 g of magnitude, the fuel cell reported a drop of 5.8% at 50 Hz, whereas at 20 Hz the performance increased by 1.3%. Although more extensive experimentation is needed to identify a relationship between magnitude and frequency of vibration affecting the performance of the fuel cell as well as a throughout examination of the liquid water formation in the cathode, this study shows that sinusoidal vibration, overall, affects the performance of PEM fuel cells.


Author(s):  
Angelo Esposito ◽  
Cesare Pianese ◽  
Yann G. Guezennec

In this work, an accurate and computationally fast model for liquid water transport within a proton exchange membrane fuel cell (PEMFC) electrode is developed by lumping the space-dependence of the relevant variables. Capillarity is considered as the main transport mechanism within the gas diffusion layer (GDL). The novelty of the model lies in the simulation of the water transport at the interface between gas diffusion layer and gas flow channel (GFC). This is achieved with a phenomenological description of the process that allows its simulation with relative simplicity. Moreover, a detailed two-dimensional visualization of such interface is achieved via geometric simulation of water droplets formation, growth, coalescence and detachment on the surface of the GDL. The accomplishment of reduced computational time and good accuracy makes the model suitable for control strategy implementation to ensure PEM fuel cells operation within optimal electrode water content. Furthermore, the model is useful for optimization analysis oriented to both PEMFC design and balance of plant.


Author(s):  
James Hinebaugh ◽  
A. Bazylak

In this work, a novel pore network model is employed to simulate water transport originating from condensation in the polymer electrolyte membrane (PEM) fuel cell gas diffusion layer (GDL). Liquid water transport follows the rules of invasion percolation with trapping, where two mobile phases are considered. Flow conditions are based on dynamic pressure changes in the network. The GDL is assumed to be a hydrophobic pore network, where capillary forces dominate over gravitational and viscous forces. The model follows a condensation based algorithm that begins with a single nucleation site from where liquid water spreads with continuing condensation. To account for a humidity gradient within the GDL, water flow is assumed to originate from condensation occurring in pores facing the cathode catalyst layer. Modelling parameters and their effect on the saturation profile are discussed. Little impact was found on the saturation profile when trapping logic was made more sophisticated, recognizing conditions leading to air trapping in a single throat. It is shown that saturation profiles for slow flow (i.e. slow condensation rates) can be predicted with reasonable accuracy from a known throat topology alone. However, as condensation rates are increased, raising network viscous forces to levels comparable to network capillary forces, the flow patterns begin to depend on a number of variables such as pore sizes and pore filling rates. At such condensation rates, flow patterns show high sensitivity to variance in condensation rates and become much less predictable from simple geometries.


Sign in / Sign up

Export Citation Format

Share Document