Numerical study on PEMFC’s geometrical parameters under different humidifying conditions

Steady-state and three-dimensional simulations were carried out to study the influences of geometrical parameters on the performance of PEMFC under different hydrating conditions. Flow fields, species transport, transport of water in polymer membrane and movement of liquid water in cathode and anode porous layers were determined, in order to accomplish a complete estimation of ohmic and concentration losses of PEMFC power. The geometrical parameters were thickness of the polymer membrane, cathode catalyst layer as well as gas channel to rib width ratio. Every simulation was made under different relative humidities of inlet flows (50 and 100%) for every change of characteristic length. Results show that the influence of the geometrical parameters on ohmic and concentration losses is of considerable importance. The performance of PEMFC is seriously affected under dehydrating conditions. However, such performance may be considerably improved by using suitable geometrical parameters. Cathode and anode liquid saturation may not only affect the transport of species, but also the polymer electrolyte water content. These results show the importance of simultaneously calculating both the water absorption and desorption through the polymer electrolyte and the liquid saturation in the cathode and anode porous mediums to obtain an actual view of ohmic and concentration losses of the PEMFC performance.     

新产品——钢带增强聚乙烯螺旋波纹管

钢带增强聚乙烯螺旋波纹管是一种创新的埋地排水管,把钢材的高刚度、高强度和聚乙烯的柔韧、耐腐结合在一起,突出的优点是环刚度高和节约原材料.     

建筑节能发展缓慢的原因及其对策

我国实施建筑节能已近10年，但仍然只停留在试点、示范的层面上，尚未扩大到整体．分析了造成建筑节能发展缓慢的原因，并提出了推行和普及建筑节能的对策．     

陕西省关中灌区灌溉耗水量与耗水结构

灌区耗水结构随着灌溉和农业耕作技术的改进,无效的蒸发、渗漏减少,有效的作物蒸腾增加。为了提高灌溉效益,一是要加强输水渠系的防渗衬砌,重点是干支渠;二是要进行农田基本建设,突出平整土地,辅以农业措施。     

夏热冬暖地区住宅平面设计与空调能耗关系分析

夏季住宅空调能耗已成为目前广州地区电力过荷的一个主要原因，而目前建筑师对住宅设计中的空调能耗因素并未有深入的考虑。本文就广州地区中高层住宅标准层平面设计中的朝向、形状、大小及层高与空调能耗关系进行了相关的分析，适用于夏热冬暖地区。     

镁法海绵钛生产工艺中大型无隔板镁电解槽的节能实践

以镁法海绵钛生产工艺中大型无隔板镁电解槽的实际节能情况为例，探讨了在镁电解生产中的非生产耗电、生产耗电、漏电等因素造成的能量浪费，阐述了生产中粗镁直流电耗、电流效率、工作电压3者之间的关系，指出了影响电解槽工作电压的有关因素及降低电解槽工作电压的途径。     

个人剂量仪两种电源电路设计的比较

个人剂量仪器一般要求采用电池供电，并且希望电池使用的时间越长越好，随着电池电压的降低，仪器的一些性能也会下降，合理的电源设计会延长电池的使用寿命，也能提高仪器性能，介绍了电池直接供电和采用电源芯片转换供电两种方法，并结合个人剂量仪主要进行了仪器功耗，电池使用寿命的比较，也进行了仪器其它性能，仪器成本，体积等方面的比较，通过比较结果，可根据仪器的实际要求来选择电源电路设计的方法。     

An on-line microcomputer-based respiratory monitor for manual materials handling

The main objective of the present study is to develop a low cost microcomputer-based respiratory system that is capable of computing the oxygen consumption and minute ventilation of individuals engaged in manual materials handling on an on-line basis. The design, specifications, and merits of the system are given. The software package developed was written in assembly language for the IBM AT personal computer.     

热轧高强钢平整机辊径参数设计技术研究

基于高强钢平整机的生产工艺特点,结合板形与辊耗问题,将带材的出口前张力与辊间压力横向分布都均匀作为目标函数,把保证所有被平整高强钢产品的机械性能满足产品大纲要求作为约束条件,提出了一套针对热轧高强钢平整机的工作辊与支承辊辊径参数设计模型.其研究结果对指导宝钢分公司1880 mm热轧平整机的工艺参数的确定与技术谈判发挥了重要作用,并具有进一步的推广价值.     

MTBE装置改造总结

对膨胀床—催化蒸馏组合工艺合成MTBE生产装置进行创新改造,使装置运行更可靠,操作更方便,能耗更低,生产更平稳。