At the beginning of the 21st century, fuel cells appear poised to meet the power needs of variety of applications. Fuel cell systems are available to meet the needs of applications ranging from portable electronics to utility power plants. In addition to the fuel cell stack itself, a fuel cell system includes a fuel processor and subsystems to manage air, water, thermal energy, and power. The overall system is efficient at full and part-load, scaleable to a wide range of sizes, environmentally friendly, and potentially competitive with conventional technology in first cost. Promising applications for fuel cells include portable power, transportation, building cogeneration, and distributed power for utilities. For portable power, a fuel cell coupled with a fuel container can offer a higher energy storage density and more convenience than conventional battery systems. With the development of improved membranes, catalysts and bipolar plates, Proton Exchange Membrane (PEM) fuel cells will play an important role in the near future as a new power source. The design and control of the fuel cells may be advanced by Computational Fluid Dynamics (CFD) techniques. CFD has been used to generate three-dimensional models of PEM fuel cells with the purpose of understanding the physics inside the fuel cells and improving the fuel cell performance. The performance of the fuel cell can be affected significantly by the heat generated inside its Proton Exchange Membrane (PEM). Further, water evaporation and condensation generated by temperature change inside fuel cell control humidity of the membrane and vary the local current density value and all of these phenomena need to be included in the models.