Velocity Measurements in a PEM Fuel Cell Manifold and Individual Cells Using Particle Image Velocimetry

Detailed measurements of flow through a model of a PEM fuel cell stack were made using Particle Image Velocimetry. The objective was to obtain high caliber sets of velocity fields in both the inlet manifold and within the cells over a range of Reynolds numbers in order to demonstrate relationships between flow distributions in the manifold and those along the cells of the stack. A scaled up model was built and placed in a wind tunnel under uniform inlet flow conditions. Using the PIV technique, instantaneous flowfields were captured and ensemble averaged to obtain mean and fluctuating velocity statistics. Reynolds numbers associated with operating conditions in the range of three to nine stoichs were studied in the experiments. Examination of instantaneous velocity distributions in the manifold demonstrated the existence of complex fluid motions towards the aft, resulting in increased velocity fluctuations in this region. Velocity fluctuations within the cells were also found to increase towards the aft of the stack. The inlet to the cells was characterized by a relatively large region of flow separation, which was strongest towards the front of the stack, but still persisted in cells towards the aft of the stack.