The Experimental Study of Water Accumulation in PEMFC Cathode Channel

2015 ◽  
Author(s):  
Ali Bozorgnezhad ◽  
Mehrzad Shams ◽  
Goodarz Ahmadi ◽  
Homayoon Kanani ◽  
Mohammadreza Hasheminasab
Keyword(s):  
Liquid Water ◽  
Internal Combustion Engines ◽  
Two Phase Flow ◽  
Gas Diffusion ◽  
Green Energy ◽  
Proton Exchange ◽  
Phase Flow ◽  
Two Phase ◽  
Coverage Ratio ◽  
Water Accumulation

In the recent years, Proton Exchange Membrane Fuel Cell (PEMFC) has attracted much attention as a source of green energy and alternative to internal combustion engines. The PEMFC produces electrical power with heat and water as only byproducts. Water is needed to providing proper hydration of membrane and its ionic conductivity in PEMFCs, but excess water accumulation known as flooding phenomenon decreases reaction sites on gas diffusion and increases mass transport loss and consequently it leads to performance loss of PEMFC. Proper water management depends on characterization and study two-phase flow phenomenon of PEMFC as flooding. In the present work, the two-phase flow in the cathode channel of transparent PEMFC with single serpentine flow field is studied by direct optical visualization and utilization of Digital Image Processing for different inlet flow parameters and operational conditions. Liquid water accumulation in the cathode channel is quantified and the water coverage ratio is calculated as a scale of water content of the cathode channel in the unsteady and time-averaged states. Increasing the temperature and stoichiometry decrease the accumulation of liquid water in the cathode channel while increasing the reactants relative humidity leads to accumulation of more liquid water. Observations show in higher cathode stoichiometries, the effect of anode stoichiometry on the water coverage ratio decreases. The effect of anode stoichiometry on the water coverage ratio is more than the cathode stoichiometry. In higher anode stoichiometries, the effect of cathode stoichiometry on the water coverage ratio decreases so that the change in cathode stoichiometry has no significant effect on the values of water coverage ratio.

Two-Phase Flow Considerations in PEMFC Design and Operation

2008 ◽  
Author(s):  
Jon P. Owejan ◽  
Jeffrey J. Gagliardo ◽  
Jacqueline M. Sergi ◽  
Thomas A. Trabold
Keyword(s):  
Liquid Water ◽  
Proton Exchange Membrane ◽  
Two Phase Flow ◽  
Bipolar Plate ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Phase Flow ◽  
Two Phase ◽  
Flowing Hydrogen ◽  
Flow Effects

A proton exchange membrane fuel cell (PEMFC) must maintain a balance between the hydration level required for efficient proton transfer and excess liquid water that can impede the flow of gases to the electrodes where the reactions take place. Therefore, it is critically important to understand the two-phase flow of liquid water combined with either the co-flowing hydrogen (anode) or air (cathode) streams. In this paper, we describe the design of an in-situ test apparatus that enables investigation of two-phase channel flow within PEMFCs, including the flow of water from the porous gas diffusion layer (GDL) into the channel gas flows; the flow of water within the bipolar plate channels themselves; and the dynamics of flow through multiple channels connected to common manifolds which maintain a uniform pressure differential across all possible flow paths. These two-phase flow effects have been studied at relatively low operating temperatures under steady-state conditions and during transient air purging sequences.

An Improved Two-Phase Flow and Transport Model for the PEM Fuel Cell

2010 ◽  
Vol 105-106 ◽  
pp. 691-694
Author(s):  
Shi Zhong Chen ◽  
Yu Hou Wu ◽  
Hong Sun ◽  
Hong Tan Liu
Keyword(s):  
Fuel Cell ◽  
Liquid Water ◽  
Mass Fraction ◽  
Water Mass ◽  
Two Phase Flow ◽  
Transport Model ◽  
Catalyst Layer ◽  
Proton Exchange ◽  
Phase Flow ◽  
Two Phase

A two-phase flow, multi-component model has been optimized for a PEM (Proton Exchange Membrane) Fuel Cell. The modeling domain consists of the membrane, two catalyst layers, two diffusion layers, and two channels. Both liquid and gas phases are considered in the entire cathode and anode, including the channel, the diffusion layer and the catalyst layer. The Gravity effect on liquid water was considered in channels. Typical two-phase flow distributions in the cathode gas channel, gas diffuser and catalyst layer are presented. Source term and porosity term were optimized. Based on the simulation results, it is found that two-phase flow characteristics in the cathode depend on the current density, operating temperature, and cathode and anode humidification temperatures. Water mass fraction for the fuel cell with anode upward is higher than that the case with cathode-upward. Liquid water with the case of cathode-upward blocks pores in the gas diffuser layer leading to increasing the concentration polarization. Gravity of liquid water exerts the effect on the water mass fraction in the cathode.

Two-Phase Flow and Transport in the Interdigitated Air Cathode of Proton Exchange Membrane Fuel Cells

2000 ◽  
Author(s):  
Z. H. Wang ◽  
C. Y. Wang
Keyword(s):  
Current Density ◽  
Liquid Water ◽  
Two Phase Flow ◽  
Water Saturation ◽  
Gas Diffusion ◽  
Phase Flow ◽  
Air Cathode ◽  
Phase Zone ◽  
Two Phase ◽  
Flow And Transport

Abstract The two-phase flow and transport in an interdigitated air cathode is studied numerically by applying the multiphase, multicomponent transport model previously developed for conventional air cathodes. A computational fluid dynamics (CFD) technique is used to solve the two-dimensional model for the interdigitated air cathode, and the contours of oxygen concentration, water vapor concentration and liquid water saturation as well as the velocity vector fields of gas and liquid phases are obtained. A polarization curve is presented which includes both the single- and two-phase operating regimes. It is found that the threshold critical current density at which the two-phase zone begins to appear inside the porous cathode is higher than that of the conventional air cathode. The maximum liquid water saturation is found to be about 0.045 for a dry inlet at an average current density of 2.07A/cm2. Both gas diffusion and convection play significant roles in oxygen supply and water removal. A higher inlet relative humidity produces a more extensive two-phase zone in the interdigitated air cathode.

scholarly journals Modeling the Effects of Using Gas Diffusion Layers With Patterned Wettability for Advanced Water Management in Proton Exchange Membrane Fuel Cells

2018 ◽  
Vol 15 (2) ◽  
Author(s):  
Jaka Dujc ◽  
Antoni Forner-Cuenca ◽  
Philip Marmet ◽  
Magali Cochet ◽  
Roman Vetter ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Two Phase Flow ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Ex Situ ◽  
Phase Flow ◽  
Mechanical Compression ◽  
Two Phase ◽  
Exchange Membrane

We present a macrohomogeneous two-phase model of a proton exchange membrane fuel cell (PEMFC). The model takes into account the mechanical compression of the gas diffusion layer (GDL), the two-phase flow of water, the transport of the gas species, and the electrochemical reaction of the reactant gases. The model was used to simulate the behavior of a PEMFC with a patterned GDL. The results of the reduced model, which considers only the mechanical compression and the two-phase flow, are compared to the experimental ex-situ imbibition data obtained by neutron radiography imaging. The results are in good agreement. Additionally, by using all model features, a simulation of an operating fuel cell has been performed to study the intricate couplings in an operating fuel cell and to examine the patterned GDL effects. The model confirms that the patterned GDL design liberates the predefined domains from liquid water and thus locally increases the oxygen diffusivity.

Ex-Situ Characterization of Two-Phase Flow Regimes in Proton-Exchange Membrane Fuel Cells Under Non-Isothermal Conditions

2010 ◽  
Author(s):  
Arganthae¨l Berson ◽  
Jon G. Pharoah
Keyword(s):  
Proton Exchange Membrane ◽  
Two Phase Flow ◽  
Metal Foam ◽  
Flow Regimes ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Ex Situ ◽  
Phase Flow ◽  
Two Phase ◽  
Exchange Membrane

Efficient water management is crucial for the good performances of proton-exchange membrane fuel cells (PEMFCs). The geometric and physical characteristics of the components of a PEMFC as well as operating conditions have an impact on the transport of water through the porous transport layer (PTL) and the two-phase flow regimes in the microchannels. One parameter of importance is the local temperature, which affects properties such as surface tension and is coupled with phase change. Indeed, a temperature difference of about 5K is expected across the PTL, with spatial variations due to the geometry of the flow field plate. We present preliminary results obtained with a first experimental setup for the ex-situ characterization of two-phase flow regimes in the flow channels. Water is pushed through the PTL, which is sandwiched between a porous metal foam and the flow field plate. The air flow rate, temperature and humidity can be controlled. The cell can be heated up by applying an electrical current through the metal foam. A transparent window is located on top of the flow channel. The two-phase flow within the micro-channels is visualized using a high-speed camera and laser-induced fluorescence. Preliminary results obtained under isothermal conditions at room temperature show that different two-phase flow regimes occur in the channels depending on the operating conditions, in good qualitative agreement with data from the literature. Eventually, a new visualization cell is presented that is expected to correct the flaws of the previous design and will allow a better thermal control. It will be possible to adjust the temperature gradient and the mean temperature in order to observe their impact on two-phase flow regimes for different types of PTL and flow rates. The results will provide a better understanding of water transport in PEMFC and benchmark data for the validation of numerical models.

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