Distributed diagnostics species distribution measurement

Chapters 4-6 address specific diagnostic methods in PEFCs. Martin et al. provide a detailed review of methods for distributed diagnostics of species, temperature, and current in PEFCs in Chapter 4. In Chapter 5, Hussey and Jacobson describe the operational principles of neutron radiography for in-situ visualization of liquid water distribution, and also outline issues related to temporal and spatial resolution. Tsushima and Hirai describe both magnetic resonance imaging (MRI) technique for visualization of water in PEFCs and tunable diode laser absorption spectroscopy (TDLAS) for measurement of water vapor concentration in Chapter 6. 

Despite the limited number of molecules that are technically detectable, the above-mentioned scenario is more than enough. Usually, one or two molecular species are observed for local concentration measurements (either spatially resolved through point-like acquisitions or imaged with field techniques). For instance, images of the distribution of hydroxil radical (OH) can be very rich in information. Rather often, this type of data is associated with other diagnostic means capable of complementary data (e.g., temperature or velocity) so that the researchers can reach a comprehensive understanding of the processes they are looking at. 

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