Evaluating cold-start behaviors of end and intermediate cells in a polymer electrolyte fuel cell (PEFC) stack

In a polymer electrolyte fuel cell (PEFC) stack, the end cells immediately adjacent to the end plates of a stack usually exhibit different cell behaviors compared to its intermediate cells. In this study, cold-start behaviors of end and intermediate cells in a fuel cell stack are numerically examined by using the three-dimensional cold-start PEFC model. The cold-start simulations show that the ice fraction in the end cell grows much faster than in the intermediate cell, indicating that the heat loss through stack end plate to the ambient is critical, determining the fate of cold-start whether cell shutdown or successful startup. As a consequence, under the assumed cold-start condition (start-up from -20 degrees C and 100 mA/cm(2)), the end cell experiences a sudden voltage drop and cold-start failure due to considerable ice filling in the cathode catalyst layer (CL) whereas a successful startup is achieved in the intermediate cell because its temperature increases faster than the rate of ice growth and finally exceeds freezing temperature. (C) 2012 Elsevier B.V. All rights reserved.