Serpentine flow-fields are widely used for polymer electrolyte membrane (PEM) fuel cells due to effective water removal. In this study, the effects of serpentine flow-field designs on the performance of a commercial-scale PEM fuel cell stack for micro-CHP (Combined Heat & Power) systems, which use reformed gas as fuel, are investigated by performing both computational fluid dynamics (CFD) simulations and experimental measurements. First, we design four different serpentine flow-fields in which the total channel area (defined as open channel area in this study) of a flow-field plate is altered without changing other design parameters such as the channel cross-sectional area and the channel length. Then, CFD simulations and experimental measurements are performed to assess the performance of each flow-field design. The CFD simulation results show that the current density distributions and average current densities are very insensitive to the open channel area. Thus, the information from the simulations is not sufficient to judge whether the open channel area affects the performance of a PEM fuel cell. On the other hand, the experimental measurements indicate that the performances of four fuel cell stacks, each with one of the four flow-field designs used in the simulations, are considerably different. Increasing the open channel area of a serpentine flow-field improves the performance of the PEM fuel cell up to a certain extent. (C) 2012 Elsevier Ltd. All rights reserved.