Page 9 - Introduction to Transfer Phenomena in PEM Fuel Cells

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