Particle Image Velocimetry Measurements

Particle image velocimetry was used to measure 2D velocity fields in representative regions of interest within flow channels of interdigitated and single-serpentine PEM fuel cell models. The model dimensions, GDL permeability, working fluid, and flow rates were selected to be geometrically and dynamically similar to the cathode-side airflow in a typical PEM fuel cell.

Figure 1 - Typical Flow Field Designs

The model was easily reconfigurable between parallel, single-serpentine and interdigitated flow fields, and was constructed from transparent materials to enable optical imaging. The use of rubber plugs allowed easy change from one flow field design to the next.

Dimensional similarity was used to design a geometrically and dynamically scaled fuel cell model. The flow conditions in the model were selected to match the cathode-side airflow in an equivalent, albeit non-reacting fuel cell. Despite this limitation, the model allows several advantages which make it overwhelmingly simpler to perform PIV measurements than in an operational fuel cell. All the walls of the model are transparent which has made it possible to measure channel convective bypass for the first time. Velocity maps were obtained of both the primary and secondary flow within the channels. Measurements of the secondary flows in interdigitated and single-serpentine flow fields indicate that significant portions of the flow travel between adjacent channels through the porous medium. Such convective bypass can enhance fuel cell performance by supplying fresh reactant to the lands regions, and also by driving out product water from under the lands to the flow channels.

Figure 2 - Velocity Fields for Interdigitated Flow Field Configuration
Figure 3 - Velocity Fields in Serpentine Flow Field Configuration
Feser J.P., Prasad A.K., and Advani S.G., "Particle image velocimetry measurements in a model proton exchange membrane fuel cell," Journal of Fuel Cell Science and Technology, Vol. 4, pp. 328-335, July 10, 2007. doi:10.1115/1.2744053