Visualization Analysis of Interrelationship between Temperature Profile and Water Distribution inside the PEFC

Introduction For more spread of Polymer Electrolyte Fuel Cells (PEFCs), water management inside it is very important. Water condensation and transportation modes are very difficult to reveal exactly, because there are many complicated phenomena inside Gas Diffusion Layer (GDL) which has fibrous structure and tiny pore diameter. Temperature profile largely affects on water distribution inside a PEFC. Therefore, we should understand interrelationship between temperature profile and water distribution inside a PEFC to optimize water distribution. There is a report [1] about interrelationship between them in which characteristics of heat transportation has been changed by changing type of GDL. However, in [1], they couldn’t clarify interrelationship because the change of heat transportation characteristics was too small. So in this report, by giving temperature gradient externally, temperature gradient inside cathode GDL of a PEFC was set. Then effects of temperature gradient in through-plane on water distribution in a PEFC is investigated. Experimental method X-ray CT X-ray CT machine, TDM1000-H-Ⅱ(2K)(Yamato Scientific Corp.) was used for visualizing water distribution inside a PEFC. By using this machine, 3-D image of a sample can be got. Total shooting time was about 15 minute. Tube voltage was 30 kV and voxel size was about 2.7 µm. Thin-Film Thermocouple (TFTC) For local temperature measurement, original sensor was fabricated using Micro Electro Mechanical Systems (MEMS) in our laboratory. The sensor was so fine and thin that it wouldn’t disturb a reaction inside a PEFC. The thermocouple was made from Au and Ni. Its measurement point had about 30 µm width and about 6 µm thickness. Cell Configuration An active area of 1 cm 2 PEFC cell was used, and is has five 1mm width gas channels and five 1mm width ribs with parallel flow configuration. 15 µm thick reinforces type PEM was used. TGP-H-060 (with MPL 2.0 mg/cm 2 ) was used and in both anode and cathode side. TFTC was inserted between interface of anode CL/MPL and cathode CL/MPL. Experimental proceed First, conditioning of CCM was performed at 0.1 V for 30 minute. Then target temperature was set by temperature controller, and steady waiting was performed for 10 minute. Then some information of a cell (cell voltage, some temperature, and so on) was recorded. Finally, visualization by X-ray CT was performed. Wet gas was supplied to a cell, and water temperature in bubblers was set to 55 ℃. Results and Discussi