Ken Okazaki

Visualization of the Membrane Temperature Field of a Polymer Electrolyte Fuel Cell

Membrane temperature field of a polymer electrolyte fuel cell (PEFC) has been visualized experimentally. PEFCs need further breakthrough for deployment in the market. One of the major issues is the temperature management of the polymer membrane and the whole cell that strongly govern system performance through electrochemical reactions, ion transport, water management, and gas supply. The temperature field of the membrane, however had not been visualized due to the cell configuration. In our experiment, the thermography technique is applied to visualize an operating test cell. Despite the unique configuration, measured i-V characteristics guarantee the cell performance. The visualization results revealed several important characteristics that help us understanding the physics and suggest design knowledge. One major result is the existence of so called a hot spot. The membrane does have a temperature distribution, and a local temperature maximum may exceed the membrane design limitation. This trend, of course, is not favorable for design purposes. Also, the impact of the major operation parameters, such as current density humidification, and gas flow configuration, have been clearly exhibited. The experimental results are examined by using the results of our previously developed numerical code. The code includes the conjugate nature of the electrochemical reaction and the heat and mass transport processes. By comparing the experiment and the calculation, the mechanisms of the hot-spot generation and the parameter dependence have been explained. The results revealed the physics and suggested essential design criteria.

Optical Measurement Technique of Water Contents in Polymer Membrane for PEFCs

The feasibility of an optical technique is examined for the measurement of the membrane water content in polymer electrolyte fuel cells (PEFCs). Transmission of the infrared light of 1.92 μm wavelength is used to measure the water content in the polymer electrolyte membrane. A calibration procedure is examined, and the technique is applied for the transient measurement of a Nafion membrane that gives the value of water diffusion coefficient, consistent with previous reports. The technique is then applied to an operating PEFC to show its applicability for in situ measurement.

Structural Effects of Cathode Catalyst Layer on the Performance of PEFC

The structure of cathode catalyst layer (CCL) has strong relationship with the performance of polymer electrolyte fuel cells (PEFCs). We investigated the relationship between the catalyst layer structure and the cell performance experimentally. Multi-layered CCL is used to investigate the effect of the layer design on the cell performance. Membrane side of CCL works, as a reaction area, more actively than the gas diffusion layer (GDL) side at low relative humidity (RH) due to the lower proton conductivity. On the other hand, when the cathode gas has less oxygen partial pressure at high RH, GDL side is more active than membrane side owing to low diffusivity of oxygen. We suggest that the volumetric catalyst concentration of the CCL membrane side should be higher at low RH, however at high RH with lower oxygen partial pressure in cathode gas, the GDL side should have higher concentration. Simple theoretical model is employed to see the behavior of the reaction distribution in the catalyst layer.Copyright

Investigation on the interactions among light, material and temperature field in transient lens effect, transmission characteristics in 1D temperature field

Recent advances in measurement techniques using the photothermal effect have drawn more and more attention to the application in various fields. Especially, laser measurements are becoming increasingly important for the thermal design of electronic devices because these measurements can be applied to non-invasive and non-destructive measurement [1, 2]. We focus on the transient lens effect, which is a well-known photo-thermal phenomenon. As this effect is caused by the change of thermal properties or other physical properties, the measurements using this effect have the possibility to measure various materials information. This phenomenon has the optical property of a concave lens since the refractive index distribution on the optical axis is formed when the liquid is irradiated. One reason for the refractive index distribution in the liquid is the temperature distribution in the liquid when it is irradiated. In this research we investigate the interaction between refractive index and temperature distribution on the Transient lens effect, in order to develop fluidic optical devices

Investigation on the interaction among light, material and temperature field in the transient lens effect

Recent advances in measurement techniques using the photo-thermal effect have drawn more and more attention to the application in various fields. Especially, laser measurements are becoming increasingly important for the thermal design of electronic devices because these measurements can be applied to non-invasive and non-destructive measurement [1, 2]. We focus on the transient lens effect, which is a well-known photo-thermal phenomenon. As this effect is caused by the change of thermal properties or other physical properties, the measurements using this effect have the possibility to measure various materials information. This phenomenon has the optical property of a concave lens since the refractive index distribution on the optical axis is formed when the liquid is irradiated. One reason for the refractive index distribution in the liquid is the temperature distribution in the liquid when it is irradiated. In this research we investigate the interaction between refractive index and temperature distribution on the Transient lens effect, in order to develop fluidic optical devices

Investigation on the Interactions Among Light, Material and Temperature Field in Transient Lens Effect

Recently, analysis and diagnosis based on laser technology is progressing rapidly by means of the advancement of the technology related to optics. It is remarkable that the technology using high intensisty laser pulses, e.g. nanosecond to femtosecond laser pulses, has advanced. Using intense laser pulses gives high industrial advantages. However, there are few reports to investigate the relation between laser pulses and liquid. In this research, we investigate the influence of the local temperature distribution generated in applications that utilized cw-laser. Furthermore, we discussed the transient lens effect that is based on the interaction between light, material and temperature field experimentally and theoretically.Copyright