Fuel cells are growing in importance as sources of sustainable energy and will doubtless form part of the changing programme of energy resources in the future. The development of physically representative models that allow reliable simulation of the processes under realistic conditions is essential to the development and optimisation of fuel cells, the introduction of cheaper materials and fabrication techniques, and the design and development of novel architectures. The strength of the CFD numerical approach is in providing detailed insight into the various transport mechanisms and their interaction, and in the possibility of performing parameters sensitivity analyses. Three-dimensional CFD models of a PEM fuel cell have been developed and presented in detail. The model was developed to improve fundamental understanding of transport and electrochemical phenomena in PEM fuel cells and to investigate the impact of various operation parameters on performance. In addition to revealing the detail of transport and electrochemical phenomena inside the PEM fuel cell, the comprehensive CFD models have been used to investigate the sensitivity of certain parameters on fuel cell performance. A parametric study using the present CFD models has been performed. A detailed analysis of the fuel cell performance under various operating conditions has been conducted and the effects of operating, design, and material parameters have been examined. The need for improved lifetime of PEM fuel cells necessitates that the failure mechanisms be clearly understood and life prediction models be developed, so that new designs can be introduced to improve long-term performance. A full three-dimensional, CFD model has been developed to investigate the mechanical, hygro and thermal stresses in PEM fuel cell, which developed during the cell operation. The behaviour of the gas diffusion layers and membrane during operation of a PEM fuel cell has been studied and investigated under real cell operating conditions. A detailed parametric study has been performed in order to study the effect of operating, design, and material parameters on the stresses in gas diffusion layers and polymer membrane. The performance of fuel cells is affected by operating point (cell voltage and related current density), operating parameters, design parameters, and material parameters. Optimisation study of a PEM fuel cell performance has been performed and discussed in detail. The CFD models are shown to be able to provide a computer-aided tool for design and optimise future fuel cell with much higher power density, long cell life, and lower cost. The book of CFD MODELS FOR ANALYSIS AND DESIGN OF PEM FUEL CELLS looks at how engineers can model PEM fuel cells to get optimal results for any application. This book is a practical summary of how to create CFD models, how to manipulate them and how to interpret results. These models would allow the creation of powerful computational fuel cell engineering tools that lead to dramatic reductions in lead times and development costs, and spur innovative design.