Cathode reaction models and performance analysis of Sm0.5Sr0.5CoO3−δ-BaCe0.8Sm0.2O3−δ composite cathode for solid oxide fuel cells with proton conducting electrolyte

Cathode reaction models for solid oxide fuel cells with proton conducting electrolyte (H-SOFC) are proposed, and the reacting orders for each elementary step with respect to oxygen and water vapor partial pressure are calculated. The limiting steps of cathode reactions are investigated with Sm_0.5Sr_0.5CoO_3−δ (SSC)-BaCe_0.8Sm_0.2O_3−δ (BCS) composite cathodes. The results suggest that the migration of protons to TPBs and the surface diffusion of might be the limiting reactions for SSC-BCS composite cathodes in wet atmosphere, while the oxygen ions transferring into electrolyte, the reducing of O_ad to , and surface diffusion of might be the limiting reactions for SSC-BCS composite cathode in dry atmosphere.     

A fiber-optic Bragg grating sensor for simultaneous static and dynamic temperature measurement on a heated cylinder in cross-flow

A fiber-optic Bragg grating (FBG) sensor is proposed to measure the local static temperature and the fluctuating temperature θ_s on the surface of a heated circular cylinder subjected to a cross-flow. In order to validate the new technique, a type-K thermocouple and a single hot wire are used to measure and the near-wake streamwise fluctuating velocity u, respectively. The FBG sensor measurement of agrees well with that simultaneously obtained by the thermocouple. The θ_s-spectrum exhibits a prominent peak at the vortex shedding frequency, (U_∞ is the free-stream velocity and d is the cylinder diameter), consistent with the u-spectrum. In fact, the θ_s and u signals are almost perfectly correlated at . Furthermore, the measured and root mean square value of θ_s are agreeable with previously reported Nusselt number data. These results demonstrate that the FBG sensor can be used to measure reliably both static and fluctuating temperatures. It is expected that the FBG sensor, because of its uniqueness in many aspects and being at an affordable cost, has an excellent prospect in temperature measurements.