The resonant frequency of water depends on the Selleck EPZ015666 temperature. The temperature dependence of the resonant frequency of 1H in water is about 0.01 ppm/°C . The temperature of MEA may rise due to heat generation in the PEFC and, as a result, the resonance frequency of 1H of water in MEA may change. When this change due to temperature rise is large, the assumption that resonance frequency changes only due to magnetic fields induced by electric current within the PEFC is not valid. When the PEFC employed generates a current of 5 A, the heat generation of the PEFC is estimated to be about 2 W. The temperature rise of the MEA due to a heat generation of 2 W is further estimated to be about 1 °C at the
most from a heat transfer analysis. When the temperature of the MEA rises by 1 °C, the change of the resonance frequency of 1H is about 0.01 ppm. On the other hand, when the PEFC used here generates an electric current of 5 A, the fluctuation of the frequency check details shift obtained from NMR signal mixed with noise is about 7–10% of the frequency shift. The corresponding variation of the measured frequency shift is from 0.7 to 5.5 ppm. Therefore, we think that the change of the resonant frequency of 1H (water) due to temperature rise of MEA hardly affects the calculation
of electric current generated in the PEFC. We can understand the electrical generation and the time dependent change of the water which has formed inside the PEFC by simultaneously measuring the spatial distributions of the water content in the PEM and the local current density within the PEFC. We expect that the system developed here will prove useful in the research into suitable control procedures and appropriate PEFC structures to allow the stable generation of electrical power in PEFCs. In order to measure the time-dependent change of the spatial distributions of current density and water content in a PEM, we have developed an eight-channel NMR system. Eight RF detection coils of 0.6 mm inside diameter were inserted in the PEFC at different positions. The Carbohydrate NMR signals from water in the PEM at these eight positions were then acquired simultaneously.
The spatial distribution of current density generated in the PEFC and the water content in the PEM could be calculated from the frequency shift and the amplitude of the obtained NMR signal. The NMR system was developed by MRTechnology, Inc., NEOMAX Engineering, Ltd. and Digital Signal Technology, Inc. The software for the NMR measurements was programmed by Mr. Seitaro Hashimoto of EXA CORPORATION. The MEA was built by Dr. Sangkun Lee and Mr. Masaaki Hirano of the Hydrogen Utilization Engineering Kyusyu University. Some parts of the fuel cells were made by FC composite Inc. and Yamato Inc. The authors wish to thank all of those mentioned above for their contributions to this study. “
“In Fig. 4 the denomination of the regions for the substances 1, 2, 3 and 5 has to be changed to that shown in the corrected figure.