【作者】 聂志华；

【导师】 郭航；

【作者基本信息】 北京工业大学 ， 热能工程， 2011， 硕士

【摘要】 小型燃料电池具有能量密度高、结构简单、清洁无污染等优点,有望成为下一代小型电子设备的电源。燃料电池中反应物的浓度、温度等参数对电池的性能、效率和燃料利用率等均有重要的影响。其中,温度在电池性能的提高上起着不可替代的作用,影响催化剂的活性、膜的含水量、传质以及电池的热管理等,因此获得燃料电池内部的温度和热流分布对提高电池的性能,改进电池的结构以及电池的热模拟有重要的指导意义。目前,国内外已经有关于运行中燃料电池内部温度分布的测试方法,但是薄膜传感器由于体积小、响应快、应用范围广等将是微小型燃料电池内部温度分布测量最具发展前景的替代品。随着燃料电池的微小型化,需要掌握电池内部电化学反应的热量收支情况,迄今为止,国内外还没有关于燃料电池内部热流密度分布直接测试方法的公开文献报道。因此,本文根据微小型燃料电池的特殊结构以及燃料电池内部热流的瞬变性,研制出一种响应速度快、灵敏度高、体积小的薄膜传感器。为了测量微小型燃料电池内部的温度和热流,选用边长为8mm,厚度为0.1mm的二氧化硅绝缘基片以及相同尺寸的石墨和不锈钢作为薄膜传感器的测头基片,根据金属薄膜的热敏性,选择铜-镍或钴-锑作为传感器的热电极材料。通过在绝缘基片上蒸镀0.08~0.09μm厚的铜-镍或钴-锑薄膜热电堆进行瞬变温度的测量;在0.15μm厚的热阻层两侧蒸镀0.08~0.09μm厚的铜-镍或钴-锑热电堆进行瞬变热流的测量。采用不锈钢或石墨作为基片时,首先要在基片上蒸镀0.1~0.15μm厚的二氧化硅绝缘层。利用本文的传导式标定系统对薄膜传感器测头进行了静态标定和动态响应测试。通过实验得出,本文研制的薄膜传感器在响应时间、应用范围和测头尺寸上存在着一定的优势,能够满足燃料电池微小空间内的瞬变温度和热流测量的需求。最后,本文利用自制的薄膜传感器进行了动态响应性能测试,验证了传感器对瞬变温度和热流的响应能力以及测试系统的可靠性。更多还原

【Abstract】 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.更多还原