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Introduction to Transfer Phenomena in PEM Fuel Cells PDF

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Introduction to Transfer Phenomena in PEM Fuel Cells Series Editor Alain Dollet Introduction to Transfer Phenomena in PEM Fuel Cells Bilal Abderezzak First published 2018 in Great Britain and the United States by ISTE Press Ltd and Elsevier Ltd Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address: ISTE Press Ltd Elsevier Ltd 27-37 St George’s Road The Boulevard, Langford Lane London SW19 4EU Kidlington, Oxford, OX5 1GB UK UK www.iste.co.uk www.elsevier.com Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. For information on all our publications visit our website at http://store.elsevier.com/ © ISTE Press Ltd 2018 The rights of Bilal Abderezzak to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress ISBN 978-1-78548-291-5 Printed and bound in the UK and US Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Chapter 1. Introduction to Hydrogen Technology . . . . . . . . . . . . . 1 1.1. Hydrogen as an energy vector . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1.1. Production methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.1.2. Storage technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.1.3. Distribution networks and associated risks . . . . . . . . . . . . . . . 10 1.1.4. Advantages and challenges to raise . . . . . . . . . . . . . . . . . . . 11 1.2. Types of fuel cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.2.1. The different fuel cell technologies . . . . . . . . . . . . . . . . . . . 13 1.2.2. Fuel cell and their applications . . . . . . . . . . . . . . . . . . . . . . 32 1.2.3. Advantages and issues to improve . . . . . . . . . . . . . . . . . . . . 34 1.3. The proton-exchange membrane fuel cell . . . . . . . . . . . . . . . . . . 35 1.3.1. The basic structure of the PEMFC . . . . . . . . . . . . . . . . . . . . 37 1.3.2. PEMFC design and configuration . . . . . . . . . . . . . . . . . . . . 45 1.3.3. Operation and aging problem . . . . . . . . . . . . . . . . . . . . . . . 47 1.3.4. The fuel cell and its technical system entourage technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 1.4. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 1.5. Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Chapter 2. Charge Transfer Phenomena . . . . . . . . . . . . . . . . . . . 53 2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 2.2. Thermodynamics and chemistry of the PEM fuel cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 2.2.1. The base reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 2.2.2. Heat reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 2.2.3. Electrical work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 vi Introduction to Transfer Phenomena in PEM Fuel Cells 2.2.4. Empty voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 2.2.5. Effect of pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 2.2.6. Effect of temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 2.2.7. Theoretical efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 2.3. The flow rates of reactants and products . . . . . . . . . . . . . . . . . . . 65 2.3.1. Oxygen flow rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 2.3.2. Hydrogen flow rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 2.3.3. Amount of water produced . . . . . . . . . . . . . . . . . . . . . . . . 67 2.4. Electrochemistry of the fuel cell . . . . . . . . . . . . . . . . . . . . . . . 67 2.4.1. Electrode kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 2.4.2. Activation energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 2.4.3. Reaction rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 2.4.4. Exchange current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 2.4.5. Current density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 2.5. Polarization phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 2.5.1. Activation polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 2.5.2. Ohmic polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 2.5.3. Concentration polarization . . . . . . . . . . . . . . . . . . . . . . . . 75 2.5.4. Real cell voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 2.5.5. Polarization curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 2.5.6. Optimum operating range . . . . . . . . . . . . . . . . . . . . . . . . . 79 2.6. Modeling of charge transfer . . . . . . . . . . . . . . . . . . . . . . . . . . 79 2.7. Overview of analytical models . . . . . . . . . . . . . . . . . . . . . . . . 79 2.7.1. Simple analytical models . . . . . . . . . . . . . . . . . . . . . . . . . 80 2.7.2. Complex analytical models . . . . . . . . . . . . . . . . . . . . . . . . 80 2.8. Empirical models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 2.9. Current transport and charge conservation . . . . . . . . . . . . . . . . . 81 2.10. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Chapter 3. Mass Transfer Phenomena . . . . . . . . . . . . . . . . . . . . . 85 3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 3.2. Flow of matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 3.3. Mass transfer by convection . . . . . . . . . . . . . . . . . . . . . . . . . . 90 3.4. Mass transfer in porous diffusers . . . . . . . . . . . . . . . . . . . . . . . 92 3.4.1. Conservation of mass . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 3.4.2. The conservation of species . . . . . . . . . . . . . . . . . . . . . . . . 93 3.4.3. Some parametric laws . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 3.5. Mass transfer in the catalyst layers (electrodes) . . . . . . . . . . . . . 101 3.5.1. Low current model (Butler–Volmer) . . . . . . . . . . . . . . . . . 102 3.5.2. Agglomerate model with strong current . . . . . . . . . . . . . . . . 103 Contents vii 3.6. Mass transfer in the membrane . . . . . . . . . . . . . . . . . . . . . . . . 105 3.6.1. Schröeder’s paradox . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 3.6.2. Microscopic scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 3.6.3. Mesoscopic scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 3.6.4. Macroscopic scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 3.6.5. Parametric laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 3.7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 Chapter 4. Heat Transfer Phenomena . . . . . . . . . . . . . . . . . . . . . 125 4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 4.2. Energy balances for a PEMFC . . . . . . . . . . . . . . . . . . . . . . . . 127 4.2.1. Energy balance for a stack . . . . . . . . . . . . . . . . . . . . . . . . 127 4.2.2. Energy balance for compounds and gases . . . . . . . . . . . . . . . 130 4.2.3. Energy balance for the gas phase . . . . . . . . . . . . . . . . . . . . . 130 4.2.4. Energy balance for the solid structure . . . . . . . . . . . . . . . . . . 131 4.3. The heat flow in the different layers of the PEMFC . . . . . . . . . . . . 131 4.3.1. Heat transfer by conduction . . . . . . . . . . . . . . . . . . . . . . . . 132 4.3.2. Heat dissipation by natural convection and radiation . . . . . . . . . 133 4.4. Thermal management in a PEMFC . . . . . . . . . . . . . . . . . . . . . . 134 4.4.1. Cooling systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 4.4.2. Convection cooling of the airflow at the cathode . . . . . . . . . . . 134 4.4.3. The effect of temperature on the performance of the PEMFC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 4.5. Heat sources in the PEMFC . . . . . . . . . . . . . . . . . . . . . . . . . . 138 4.5.1. In the polymer membrane . . . . . . . . . . . . . . . . . . . . . . . . . 140 4.5.2. At the electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 4.5.3. In the GDLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 4.5.4. Water evaporation and condensation . . . . . . . . . . . . . . . . . . 145 4.6. Temperature distribution between two cathodes: case study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 4.7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 List of Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 Preface The recognition of new sources of energy that are green and renewable is a necessity for young audiences in the scientific and technical field. These non-polluting energies contribute to a more protected environment against dangerous emissions, such as greenhouse emissions or those that affect air quality. The operating principles of energy conversion devices that convert these renewable sources into useful energy must be known and controlled. This educational book develops a broad overview of the different physical phenomena that take place within a fuel cell. This book is intended for students and young researchers in technical fields. It is essentially composed of five sections as follows. Chapter 1 introduces hydrogen as an energy vector that can be produced in different ways and used in many applications. The different fuel cell technologies are presented in this chapter. A special interest in the proton-exchange membrane fuel cell is presented at the end of this chapter. In addition, a quiz specific to this introduction is provided as a good summary of the principles of hydrogen technology and PEM fuel cells. In Chapter 2, charge transfer phenomena are discussed. This chapter covers the thermodynamic and chemistry aspects of a fuel cell, the flow rates of the reactants and products as well as some electrochemical notions. At the end of the chapter, polarization phenomena and an overview of charge transfer models are described.

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