Determination of Local Conditions in PEFCs by Combining Spatially Resolved Current Density Measurements With Real-Time Modelling

2008 ◽  
Author(s):  
T. Kno¨ri ◽  
M. Schulze ◽  
K. A. Friedrich
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Real Time ◽  
Current Density ◽  
Gas Flow ◽  
Gas Diffusion ◽  
Operating Conditions ◽  
Polymer Electrolyte Fuel Cell ◽  
Spatially Resolved ◽  
Serpentine Flow Field

In this contribution a simplified, isothermal, two-phase, one-dimensional model for the calculation of the cathodic gas flow along the flow field channels of a polymer electrolyte fuel cell (PEFC) are presented. The composition of the humidified oxidant gas, average gas velocity, pressure drop, and other quantities can be calculated for different gas distributor structures. Thereby, the model requires several input parameters determined solely by experiment and operation conditions, e.g. the water content of the feed gas, local current densities, and gas flow rates. In contrast to other models, the cross-section reduction has been taken into account which results from the penetration of the gas diffusion layer (GDL) into the flow field channels due to the mounting pressure. Beyond this, the model needs no fit-parameters for further adjustment. For investigating the factors limiting the performance of a PEFC, the DLR has developed several techniques for measuring the spatially resolved current density distribution [1–5]. In order to investigate the origin of the corresponding effects, one of these techniques has been improved by implementing the model of the cathodic gas flow as an on-line feature. The combination of a spatially resolved measurement technique with a real-time simulation gives a better understanding of the local processes within the cell and represents a helpful tool for the development of fuel cell components as well as for the optimization of the operating conditions. In the presentation the results for a 25 cm2 serpentine flow field at different operation modes are shown.

In-Situ and Ex-Situ Investigation of Lateral Current Density Variations in a PEM Fuel Cell With Serpentine Flow Field

2009 ◽  
Author(s):  
Andrew Higier ◽  
Hongtan Liu
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Contact Resistance ◽  
Current Density ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Operating Conditions ◽  
Ex Situ ◽  
Serpentine Flow Field

One of the most common types of flow field designs used in proton exchange membrane (PEM) fuel cell is the serpentine flow field. It is used for its simplicity of design, its effectiveness in distributing reactants and its water removal capabilities. The knowledge about where current density is higher, under the land or the channel, is critical for flow field design and optimization. Yet, no direct measurement data are available for serpentine flow fields. In this study a fuel cell with a single channel serpentine flow field is used to separately measure the current density under the land and channel on the cathode. In this manner, a systematic study is conducted under a wide variety of conditions and a series of comparisons are made between land and channel current density. Results show that under most operating conditions, current density is higher under the land than that under the channel. However, at low voltage, a rapid drop off in current density occurs under the land due to concentration losses. In order to investigate the cause of the variations of current density under the land and channel and series of ex-situ and in-situ experiments were conducted. In the ex-situ portion of the study, the contact resistance between the gas diffusion electrode (GDE) and the graphite flow plate were measured using an ex-situ impedance spectroscopy technique. The values of the contact resistance under the channel were found to be larger than that under the land. This implies that the contact resistance under the land and channel vary greatly, likely due to variations in compression under different section of the flow field. These variations in turn cause current density variations under the land and channel.

Experimental Investigation of Proton Exchange Membrane (PEM) Fuel Cell Using Different Serpentine Flow Channels

2019 ◽  
Vol 969 ◽  
pp. 461-465
Author(s):  
Matha Prasad Adari ◽  
P. Lavanya ◽  
P. Hara Gopal ◽  
T.Praveen Sagar ◽  
S. Pavani
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Current Density ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Bipolar Plates ◽  
Flow Channels ◽  
Serpentine Flow Field ◽  
Exchange Membrane ◽  
Effective Distribution

Proton exchange membrane fuel cell (PEMFC) system is an advanced power system for the future that is sustainable, clean and environmental friendly. The flow channels present in bipolar plates of a PEMFC are responsible for the effective distribution of the reactant gases. Uneven distribution of the reactants can cause variations in current density, temperature, and water content over the area of a PEMFC, thus reducing the performance of PEMFC. By using Serpentine flow field channel, the performance is increased. Two types of serpentine flow field channels are implemented such as curved serpentine flow field channel and normal serpentine flow field channels. The result shows that curved serpentine flow field channel gives better current density and power density, thus increasing the performance of PEMFC.

Measurement of Water Production Behavior, Temperature, and Current Density Distributions in a Polymer Electrolyte Fuel Cell

2006 ◽  
Author(s):  
Takemi Chikahisa ◽  
Yutaka Tabe ◽  
Kazushige Kikuta ◽  
Naofumi Nohara ◽  
Hideki Shinohara
Keyword(s):  
Fuel Cell ◽  
Current Density ◽  
Water Distribution ◽  
Gas Diffusion ◽  
Feedback Mechanism ◽  
Polymer Electrolyte Fuel Cell ◽  
Water Production ◽  
Local Current ◽  
Production Behavior ◽  
Positive Feedback Mechanism

This paper observes phenomena related to water production behavior inside a fuel cell and analyzes the effect on the current and temperature distribution across the reaction area. A fuel cell permitting direct observation of the phenomena in the cell, 2-D temperature measurements in the cathode channels, and local current density measurements on the anode side was manufactured. The experimental results showed the production and flow of liquid water in the cell, and there were good correlations among the distributions of current density, temperature, and water amounts in the channels. The behavior of current, voltage, water distribution, and pressure differences in the cathode channels were used to hypothesize about the possibility of gas paths deep in the gas diffusion layer in the flooded condition and a positive feedback mechanism in the drying-out condition.

The Influence of a Novel Bio-Cell Flow Field Pattern on the Performance and Operating Conditions for a PEM Fuel Cell

2005 ◽  
Author(s):  
Fang-Bor Weng ◽  
Ay Su ◽  
Kai-Fan Lo ◽  
Cheng-Hsin Tu
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Gas Diffusion ◽  
Cell System ◽  
Operating Conditions ◽  
Cell Performance ◽  
Channel Structure ◽  
Field Pattern ◽  
Fuel Cell Performance ◽  
Stable Performance

A novel bio-cell flow field pattern is experimentally investigated by determining fuel cell performance and optimal operating conditions. The cell performance is analyzed by the polarization curve and the long-term stability. The bio-cell flow channel structure has a main feed track, a secondary branch track, and repeats to promote water removal from gas diffusion layer. The performance of the bio-cell flow field pattern is optimal performance when the cell is operated with low humidity gases and low cell temperature. In addition, the bio-cell flow field exhibits stable performance for non-humidified air. The fuel cell with the novel bio-cell flow field has advantages for low relative humidity operations. The results of the bio-cell flow field could potentially simplify fuel cell system design without humidifiers.

Analysis of Water Morphology in the Active Area and Channel-to-Manifold Transitions of a PEM Fuel Cell

2014 ◽  
Author(s):  
Daniel J. Fenton ◽  
Jeffrey J. Gagliardo ◽  
Thomas A. Trabold
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Flow Field ◽  
Current Density ◽  
Liquid Water ◽  
Pem Fuel Cells ◽  
Operating Conditions ◽  
Active Area ◽  
Water Volume ◽  
Crossover Point

To achieve optimal performance of proton exchange membrane (PEM) fuel cells, effective water management is crucial. Cells need to be fabricated to operate over wide ranges of current density and cell temperature. To investigate these design and operational conditions, the present experiment utilized neutron radiography for measurement of in-situ water volumes of operating PEM fuel cells under varying operating conditions. Fuel cell performance was found to be generally inversely correlated to liquid water volume in the active area. High water concentrations restrict narrow flow field channels, limiting the reactant flow, and causing the development of performance-reducing liquid water blockages (slugs). The analysis was performed both quantitatively and qualitatively to compare the overall liquid water volume within the cell to the flow field geometry. The neutron image analysis results revealed interesting trends related to water volume as a function of time. At temperatures greater than 25°C, the total liquid water volume at start-up in the active area was the lowest at 1.5 A/cm2. At 25°C, 0.1 A/cm2 performed with the least amount of liquid water accumulation. However, as the reaction progressed at temperatures above 25°C, there was a crossover point where 0.1 A/cm2 accumulated less water than 1.5 A/cm2. The higher the temperature, the longer the time required to reach this crossover point. Results from the current density analysis showed a minimization of water slugs at 1.5 A/cm2, while the temperature analysis showed unexpectedly that, independent of current density, the condition with lowest water volume was always 35°C.

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