Numerical modeling and analyses of anisotropic diffusion and stresses in polymer electrolyte fuel cell

Download

index.pdf

Date

2017

Author

Mehrtash, Mehdi

Metadata

Show full item record

Item Usage Stats

225
views

81
downloads

A two dimensional, half-cell, non-isothermal, multi-phase model of a polymer electrolyte fuel cell (PEFC) is developed. The model accounts for the acting clamping force on the cell with accompanying effects on gas transport properties and contact resistances. Spatial variations of anisotropic structural and physical properties of gas diffusion layers (GDLs) in both in-plane and through-plane directions are considered. The developed mechanistic model is validated by comparıng its results with the experimental data for voltage-current characteristics and channel-rib current density distribution for the first time in literature. Significant changes are observed in local gas and water concentrations as well as current density profiles with respect to cell compression and humidity ratios of entrant gases. Compression exacerbates the liquid saturation under the rib as a consequence of porosity and permeability reduction. Under compression, phase change rate increases in the cell; degree of supersaturation under the channel escalates leading to a higher condensation rate while degree of undersaturation under the rib increases leading to a higher evaporation rate. Low durability of membranes is one of the major barriers for wide spread commercialization of PEFCs. The swelling effect on durability is one of the key challenges for the fabrication of the catalyst-coated membrane at the heart of the PEFC. Presented in this study were three main contributions that provide insight into the probable locations of failure in the membrane under hygrothermal cycle and external applied force, and the realistic conditions where a combination of both these loadings were applied. Mechanical response of the membrane, subjected to conjugate hygro-thermo-mechanical loadings are observed during fuel cell operation. The effects of different operating parameters as well as individual contributing factors on the local stresses induced in the membrane are identified.

Subject Keywords

Fuel cells., Anisotropy., Electrolytes.

URI

http://etd.lib.metu.edu.tr/upload/12621270/index.pdf
https://hdl.handle.net/11511/26535

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Impacts of inhomogeneous clamping force on local performance and liquid water formation in polymer electrolyte fuel cells Mehrtash, Mehdi; Tarı, İlker; Yesilyurt, Serhat (Elsevier BV, 2017-7) A two dimensional, half-cell, non-isothermal, multi-phase model of a polymer electrolyte fuel cell (PEFC) is developed. The model accounts for the acting clamping force on the cell with accompanying effects on gas transport properties and contact resistances. Spatial variations of anisotropic structural and physical properties of gas diffusion layers (GDLs) in both in-plane and through-plane directions are considered. Designed mechanistic model is compared and validated with the experimental data for voltag...
Numerical investigation of a stand alone solar hydrogen energy system effects of PEFC degradation Ender, Ozden; Tarı, İlker (null; 2015-08-12) An existing stand-alone solar energy system producing hydrogen for energy storage is numerically investigated focusing on the degradation of Polymer Electrolyte Fuel Cell (PEFC) and its effects on the overall performance of the system. The system consists of Photovoltaic (PV) panels, polymer electrolyte based electrolyzers, H2 and O2 storage tanks and a commercial PEFC stack. A PEFC is numerically investigated both as new and as degraded (for about two years). Using a variety of observed degradation pattern...
Numerical Investigation of thermal management of Solid Oxide Fuel Cells by flow arrangement Şen, Fırat; Tarı, İlker (null; 2015-05-29) SolidOxide Fuel Cells (SOFCs) are electrochemical cells working at high temperatures. One of the important problems in planar SOFC designs is the non-uniformtemperature distribution on the plane of the cell due to the waste heat produced by electrochemical reactions. Another important problem of SOFCs is the low fuel utilization ratio. In this study, the effect of the flow arrangement on the temperature distribution, which causes the thermal stresses, and the met...
Development of 100w portable fuel cell system working with sodium borohydride Erkan, Serdar; Eroğlu, İnci; Department of Chemical Engineering (2011) Fuel cells are electricity generators which convert chemical energy of hydrogen directly to electricity by means of electrochemical oxidation and reduction reactions. A single proton exchange membrane (PEM) fuel cell can only generate electricity with a potential between 0.5V and 1V. The useful potential can be achieved by stacking cells in series to form a PEM fuel cell stack. There is a potential to utilize 100W class fuel cells. Fuelling is the major problem of the portable fuel cells. The aim of this th...
Development of 500 W PEM fuel cell stack for portable power generators DEVRİM, YILSER; Devrim, Huseyin; Eroğlu, İnci (2015-06-29) Polymer Electrolyte Membrane Fuel Cell (PEMFC) portable power generators are gaining importance in emergency applications. In this study, an air-cooled PEMFC stack was designed and fabricated for net 500 W power output. Gas Diffusion Electrodes (GDE's) were manufactured by ultrasonic spray coating technique. Stack design was based on electrochemical data obtained at 0.60 V was 0.5 A/cm(2) from performance tests of a single cell having the same membrane electrode assemblies (MEA) that had an active area of 1...

Citation Formats

M. Mehrtash, “Numerical modeling and analyses of anisotropic diffusion and stresses in polymer electrolyte fuel cell,” Ph.D. - Doctoral Program, Middle East Technical University, 2017.