A novel design for humidifying an open-cathode proton exchange membrane fuel cell using anode purge

The low performance of open-cathode proton-exchange-membrane fuel cells (OCPEMFCs) is attributed to the low-humidity ambient air supplied to the cathode using electric fans. To improve the OCPEMFC performance, this paper proposes a novel humidification method by collecting water purged from the anode and supplying it to the open cathode. The OCPEMFC performance is evaluated at various humidifier distances from the cathode inlet, and it is compared with that where no humidifier is used when the OCPEMFC operates under three different current levels of 1, 5, and 8 A. The results show that the novel design improves the stack power, and optimal performance is achieved at a humidifier distance of 2 cm. The energy efficiency achieves an improvement between 1.4% and 1.8% when a humidifier is used.     

Characteristics of membrane humidifiers for polymer electrolyte membrane fuel cells

Water management plays an important role in obtaining high performance from a polymer electrolyte membrane fuel cell (PEMFC). To reduce the volume and energy consumption of widely-used bubble humidifiers, membrane humidifiers were fabricated by using an ultrafiltration (UF) membrane and Nafion membranes. The performance of the membrane humidifiers was examined as a function of gas flow rate and operating temperature. A single cell was operated using the UF membrane humidifiers exhibiting almost the same performance with that employing bubble humidifiers.     

Heat and mass transfer characteristics in a spray chamber

This paper presents a one-dimensional mathematical model for heat and mass transfer of water droplets in a spray chamber. The model includes drop size distribution and velocity of the droplets generated by a nozzle of inlet diameter 3.2 mm. By using the conservation of mass and energy, the changes in water temperature, air temperature and humidity along the spray cone in the spray chamber can be calculated. This model is tested with two different water mass flows. The results look reasonable from practical point of view and they also show that higher water mass flow results in a higher air temperature drop and higher humidity.     

关于无梭织机车间除尘、空调与加湿的讨论

针对无梭织机车间的特点,分别对解决车间除尘,空调加,加湿三大问题的方法和措施进行了讨论,介绍了国外较为成熟的中央真空吸尘系统和国内开发的双风机真空吸尘系统的应用与效果,以喷雾风机为核心的节能空调系统以及四种送回风方式的应用实例,辅助加湿系统的采用 新型KS系列加 湿器性能。     

Experimental study on water transport in membrane humidifiers for polymer electrolyte membrane fuel cells

This paper presents an experimental setup for the measurement of water transfer in membrane humidifiers for automotive polymer electrolyte membrane (PEM) fuel cells at different process conditions. This setup was used to determine steady-state water permeation through perfluorinated sulfonic acid (PFSA)-based polymer membranes. The process conditions were varied within a relative humidity in the feed stream of RH = 30–90 %, absolute pressures of p = 1.25–2.5 bar, and temperatures of T = 320–360 K. The examined membranes are Nafion® membranes of different thicknesses (Nafion® 211, 212 and 115) and an experimental composite membrane manufactured by W. L. Gore & Associates. It was found that the overall water permeance is affected by both the mass transfer resistance of the membrane and the resistances in the boundary layers of the adjacent gas streams. The overall permeance is a strong function of water activity, with high levels of relative humidity showing the highest overall permeance. The absolute pressure only affects the overall permeance by affecting the diffusion in the boundary layers. Lower pressures are preferable for high overall water permeances. Increasing temperatures favor diffusion in the membrane and the boundary layers but lead to lower sorption into the membrane. The thicker Nafion® membranes show lower overall permeance at higher temperatures, while the overall permeance of the composite membrane shows no dependency on the temperature. Investigation of membrane humidifiers in counter-, co-, and cross-flow shows that the flow configuration in our setup has very little impact on the water flux in the humidifier.     

国内外纺织厂空气加湿技术的发展

系统介绍了国内外纺织厂空气加湿技术的现状，介绍了空调系统加湿和车间直接加湿的各种形式，现有各种纺织空气加湿设备的功能特性、适用场所，分析了目前空气加湿技术存在的主要问题，指出了今后空气加湿技术的发展方向。     

纺纱抓棉过程加湿方法探讨

探讨纺纱生产抓棉过程加湿方法。介绍分析了纤维吸放湿的影响因素,包括纤维性质、纤维紧密状态、不同加工工艺等;针对抓棉过程加湿方法,介绍了抓棉机的工艺特点、抓棉过程加湿的基本要求和原理;重点介绍了圆盘抓棉过程加湿和往复抓棉过程加湿,并分别分析了两种抓棉过程加湿的控制过程;总结了抓棉过程加湿的注意事项,并分析了抓棉过程加湿效果。认为:抓棉过程加湿是一种针对性强、见效快且能显著减少用工,提高纤维回潮率的新方法。     

BTJS-IS型高压喷雾系统在纺织厂的应用

探讨高压喷雾系统在纺织厂的应用效果。介绍了高压喷雾系统的原理,对比分析了在清棉车间和剑杆织机车间安装BTJS-IS型高压喷雾系统前后加湿情况,并与空调室加湿的效果及运行成本进行了对比。结果表明:高压喷雾系统加湿的稳定性比空调室差,但其雾化效果好,加湿能力强,成本低,安装使用方便。认为:高压喷雾系统更适合相对湿度要求较高和需要进行改造的生产车间。     

Design methodology for membrane-based plate-and-frame fuel cell humidifiers

Currently, polymer electrolyte membrane fuel cells require some method of humidification to operate effectively. External gas-to-gas membrane-based humidifiers can provide an efficient method to recycle exhaust heat and product water from the fuel cell stack. This work describes a design methodology involving a series of design equations for plate-and-frame membrane humidifiers. Humidifiers of different flow channel geometries were created with a rapid prototyping technique. These humidifier units were tested at different operating conditions in an attempt to validate the design equations. The ratio between the residence time of gas in the humidifier over the diffusion time of water from the surface of the membrane into the channel can be used as a design parameter. This ratio was shown to offer a good starting point for humidifier design, and a target range between 2.0 and 4.0 was identified (with a nominal desired value of 3.0). A humidifier design procedure and suggestions are presented based on this parameter and the packaging requirements of the humidifier in a fuel cell system. This algorithm was validated by creating a further prototype humidifier.