The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Modelling Approaches to Mass Transfer and Compression Effects in Polymer Electrolyte Fuel Cells

Suvi Karvonen

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Science for public examination and debate in Auditorium K216 at the Aalto University School of Science (Espoo, Finland) on the 25th of November 2011 at 12 noon.

Overview in PDF format (ISBN 978-951-38-7755-2)   [791 KB]
VTT Publications 772, ISSN 1455-0849

Dissertation is also available in print (ISBN 978-951-38-7754-5)
Copyright © 2011 VTT Technical Research Centre of Finland
VTT Publications 772, ISSN 1235-0621
VTT-PUBS-772

Abstract

The subject of this thesis is modelling polymer electrolyte membrane fuel cells (PEMFCs) locally and on a cell scale. The modelling was done using software based on the finite element method and focused on mass transfer issues and compression pressure distribution and its effects on local phenomena.

Mass transfer, more specifically the flow distribution in the flow field system, was studied on the cathode. The velocity distribution was improved by changing the geometry of the channel system. This improvement was also observed experimentally. Mass transport problems of free-breathing fuel cells were also studied. These cells rely on free convection to provide reactants and remove reaction products. In this thesis, the aim was to develop an accurate model that is also computationally light.

The compression distribution in a stack was modelled based on an existing stack design. The results showed poor internal pressure distribution, with most of the cell experiencing insufficient compression. The modelling was then used to find a better end plate structure and suitable torques for the nut and bolt assemblies. The results were validated experimentally.

The effect of compression was studied on a local scale on which compression variations caused by the channel structure had been seen to affect the gas diffusion layer properties and contact resistances between components. According to the modelling results, there are strong local transversal electric currents in the cell. This phenomenon can affect the cell performance and lifetime negatively.

This thesis consists of an overview and of the following 5 publications:

  1. Suvi Karvonen, Tero Hottinen, Jaakko Saarinen, and Olli Himanen. 2006. Modeling of flow field in polymer electrolyte membrane fuel cell. Journal of Power Sources, volume 161, number 2, pages 876-884. © 2006 Elsevier. By permission.
  2. Tero Hottinen, Olli Himanen, Suvi Karvonen, and Iwao Nitta. 2007. Inhomogeneous compression of PEMFC gas diffusion layer: Part II. Modeling the effect. Journal of Power Sources, volume 171, number 1, pages 113-121. © 2006 Elsevier. By permission.
  3. I. Nitta, S. Karvonen, O. Himanen, and M. Mikkola. 2008. Modelling the effect of inhomogeneous compression of GDL on local transport phenomena in a PEM fuel cell. Fuel Cells, volume 8, number 6, pages 410-421. © 2008 Wiley-VCH Verlag. By permission.
  4. Suvi Karvonen, Tero Hottinen, Jari Ihonen, and Heidi Uusalo. 2008. Modeling of polymer electrolyte membrane fuel cell stack end plates. Journal of Fuel Cell Science and Technology, volume 5, number 4, 041009, 9 pages. © 2008 American Society of Mechanical Engineers (ASME). By permission.
  5. Suvi Karvonen. Modeling free convective mass and heat transfer in fuel cells. Journal of Fuel Cell Science and Technology, submitted for publication. © 2011 by author and © 2011 American Society of Mechanical Engineers (ASME). By permission.

Keywords: PEMFC, fuel cell, modelling

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© 2011 Aalto University

Last update 2011-11-28