Experimental Study Of Transient Heat Flux Sensor For Parameters Measurement Inside Small Fuel Cells

Small fuel cells are one of the most promising candidates for the next generation power sources of the miniature electronic devices due to their high energy density, simple structure, clean and so on. It is essential to control the parameters, such as reactants concentration and temperature, for they have important influence on the performance, efficiency and fuel utilization of the micro fuel cells. Of which, temperature plays an important role in achieving high performance of the fuel cells because it greatly affects the activity of catalyst, dehydration of polymer membrane, mass transfer and heat management of fuel cells. Therefore, getting the temperature distribution inside the fuel cells has guiding significance in achieving high performance, modulating the structure, modeling and simulation.To date, several studies have been conducted in order to monitor the temperature variations inside micro fuel cells, but thin film thermocouples are the most promising candidates among various types of temperature sensors for measuring temperature inside a operating fuel cell because of their small size, fast response and widely application range.With the miniaturization of fuel cells, the heat generated from electrochemical reaction inside the cells need to be mastered. There has not publicly reported domestic and abroad about the direct testing methods on the heat flux density inside fuel cells. Therefore, according to the special structure and the transient properties of the heat flux inside the fuel cells, this paper developed a thin-film sensor with the merits of fast response, high sensitivity and small size.In order to measure the temperature and heat flux inside the micro fuel cells, choosing the insulating silicon dioxide substrate with length of 8mm, width of 8mm, thickness of 0.1mm and the same size of graphite and stainless steel as the sensors substrate, according to the heat-sensitive of the metal film, select the Cu-Ni or Co-Sb as the thermal electrode materials for the thin film sensors. By evaporate thickness of 0.08~0.09μm Cu-Ni or Co-Sb thin film thermopiles on the insulating substrates for temperature measurements; By depositing of 0.08~0.09μm thick Cu-Ni or Co-Sb thermopile on both sides of the 0.15μm thick thermal resistance layer for heat flux measurements. When use stainless steel or graphite as the substrate, we need to deposit silicon dioxide insulation layer with the thickness of 0.1~0.15μm on the substrate first.The thin film sensors are calibrated and tested using this conduction calibration system. The experiment results proved that the thin film sensors have some advantages in response speed, application range and dimensions, which can satisfy the requirement of transient temperature and heat flux measurement inside the micro space of the fuel cells.Finally, dynamic response characteristics of the thin film sensors are tested, the response ability to transient heat flux change of the sensors and the feasibility of the testing system are verified.