A chaotic heat-exchanger for PEMFC cooling applications

High-efficiency cooling systems are key points in PEMFC transport applications, as the volume constraints force the reduction of the stack size while increasing the power density. Moreover, to ensure an optimal electrochemical reaction over the whole polymer membrane surface and hence a maximum efficiency, the temperature field in the cell must be uniform and stay in a narrow range, around 80-90 degrees C. This study focuses on improving the thermal performance of heat-exchangers integrated in the bipolar plates of PEMFCs. The current design of the heat-exchangers in these applications is quite simple; cooling liquid (water) flows in straight channels or serpentines in the rear of the plates. The flow regime is laminar with a Reynolds number around 200. In order to enhance convective heat transfer, we propose here to promote three-dimensional flow inside cooling channels using a novel channel geometry that generates chaotic advection flow. However, to limit the size and the electric resistance of the bipolar plates, the thickness must be severely limited. This work concentrates on developing and characterizing heat-exchangers that can be easily reduced in size while preserving high thermal performance. (c) 2005 Elsevier B.V. All rights reserved.