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Research Papers

In Situ Fuel Cell Water Metrology at the NIST Neutron Imaging Facility

[+] Author and Article Information
D. S. Hussey, D. L. Jacobson, M. Arif

 National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 8461, Gaithersburg, MD 21701

K. J. Coakley, D. F. Vecchia

 National Institute of Standards and Technology, 325 Broadway, Mail Code 898.03, Boulder, CO 80305

Certain trade names and company products are mentioned in the text or identified in an illustration in order to adequately specify the experimental procedure and equipment used. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products are necessarily the best available for this purpose.

J. Fuel Cell Sci. Technol 7(2), 021024 (Jan 25, 2010) (6 pages) doi:10.1115/1.3007898 History: Received June 19, 2007; Revised May 05, 2008; Published January 25, 2010; Online January 25, 2010

Neutron imaging has been demonstrated to be a powerful tool to measure the in situ water content of commercial proton exchange membrane fuel cells (PEMFCs) in two and three dimensions. The National Institute of Standards and Technology neutron imaging facility was designed to produce a high intensity, highly collimated neutron imaging beam to measure the water content of operating fuel cells. The details of the neutron optics and neutron detection are discussed in terms of the random uncertainty in measuring the liquid water thickness that is typical of operating PEMFCs.

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Figures

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Figure 1

Schematic of the NIST neutron imaging facility

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Figure 2

Amorphous silicon and MCP detector cuvet images used in obtaining μw for each detector. Amorphous silicon images: (a) raw image of the wet cuvet, (b) raw image of the dry cuvet, (c) transmission image (I∕I0), and (d) grey scale image of the region from which the optical density was calculated. MCP detector images: (e) raw image of the wet cuvet, (f) raw image of the dry cuvet, (g) transmission image (I∕I0), and (h) grey scale image of the region from which the optical density was calculated.

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Figure 3

(a) The measured optical density versus step thickness for the amorphous silicon detector, and (b) the residual of the fit. (c) The measured optical density versus step thickness for the MCP detector, and (d) the residual of the fit. The Eq. 1 model was fit to data corresponding to step thickness 0mmto1mm for both data. The deviation from the linear fit in (a) is due to beam hardening.

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Figure 4

The measured random uncertainty for (a) the amorphous silicon detector and (b) the MCP detector. The amorphous silicon panel has a variation that is about 14 times less than the Poisson estimate, and the source of this discrepancy is likely due to light blooming correlating neighboring pixels and is under investigation. The MCP detector liquid water uncertainty is slightly larger than that of the simple Poisson-based estimate, which is to be expected.

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