Calculation methods for comparing the performance of pure and mixed working fluids in heat pump applications

Three methods for comparing cycle performance of working fluids, pure as well as non-azeotropic mixtures, are investigated for two applications and for two mixture pairs, HCFC22-CFC114 and HCFC22-HCFC142b, and their pure components. The methods differ in the way of calculating the heat exchange processes. They assume, respectively, equal minimum approach temperatures, equal mean temperature differences and equal heat transfer areas. Changes of coefficient of performance (COP) with composition are explained for all methods. It is shown that transport properties must be taken into account when making rigorous comparisons between working fluids. To predict the relations between fluids with high accuracy, one must use the method with equal heat transfer areas. By the method with equal mean temperature differences, the COP can be estimated with the same accuracy for mixtures as for pure fluids, and can be used for rough estimations of the COP level with different fluids. The method of equal minimum approach temperatures should be avoided for non-azeotropic mixtures.     

碳基钨涂层在退火过程中的组织和结构变化

用真空等离子体喷涂(VPS)技术在C／C复合材料基体上制备了厚度为0．5mm的钨(W)涂层，涂层的表面通过物理气相沉积(PVD)预沉积钨、铼(Re)多层作为碳(C)的扩散势垒。涂层经过1200℃--2000℃的电子束退火，其微观结构和化学构成发生变化。经测量涂层的再结晶温度约为1400℃，再结晶的活性能为63kJ／mol。当退火温度高于1300℃时，涂层表面的多层W、Re结构将由于W、Re和C之间的相互扩散而发生改变，并在1600℃以上退火lh后由于脆性碳化钨在界面的形成而完全失效，碳化钨层的厚度将随着退火漏度的升高和退火时间的延长而迅速增加。     

基于TDC控制系统的GDM通讯在宽厚板中的应用

本文以宽厚板自动控制系统为例,详细介绍了西门子TDC控制系统的特性及其应用特点,重点突出GDM全局数据内存网的软硬件配置实现方式,为那些对控制任务实时性要求很高,需高速控制和高速通讯的控制系统的实现提供了可借鉴依据。     

利用Moodle构建高校计算机基础教育-CFC的网络教学平台

CFC框架是进行计算机应用教育的主要依据,但符合各高校实际需求的CFC网络课程体系十分缺乏.本文主要论述了实施CFC的所面临的核心问题、利用Moodle搭建CFC网络课程体系的一般方法与模式、以及对如何更好地发挥Moodle网络教学功能提出了几点建议.     

冲击作用下碳纤维混凝土的力敏性试验研究

碳纤维混凝土(CFC)具有良好的力敏特性,能制成传感器用于混凝土结构的状态监测.利用钢球自由落体撞击圆柱形试样,进行了老化前后和不同撞击高度的试验,并分析了各因素对试样力敏性的影响.试验结果表明:试样的电阻变化对冲击作用响应快;老化前的试样在承载较小时,试样处于弹性区,电阻随压力增大而减小,承载较大时,试样进入弹塑性区,电阻随压力增大而增大;老化后的试样,承载即进入弹塑性区.     

21世纪的"绿色燃料"--二甲醚

被称为 2 1世纪“绿色燃料”的二甲醚具有清洁、低毒性、低蒸气压和优良的燃烧性能 ,因而成为多种产品的替代品 ,如环境友好的民用燃料、柴油和制冷剂 ,而且具有较好的市场潜力。本文主要介绍了二甲醚的生产方法、用途和国内外的发展状况     

活性炭纤维吸附装置在发泡剂CFCs回收中的应用

在冰箱拆卸过程中，聚氨酯硬质泡沫会释放出大量CFCs，而CFCs是重要的温室气体之一，因此，冰箱拆卸过程中尾气中CFCs回收受到大家重视。本文介绍了利用活性炭纤维回收家电拆卸过程中释放出氟里昂的装置。该装置自动运行，工艺先进，并且利用高效的吸附剂一活性炭纤维。运行实践表明，利用该装置可以有效的处理冰箱拆卸过程中释放出的CFCs。     

Mechanical and thermo-physical characterization of three-directional carbon fiber composites for W-7X and ITER

Carbon fiber composites (CFCs) are the first choice as plasma facing materials for the strike points of divertor targets for future nuclear fusion devices like WENDELSTEIN 7-X and ITER. For the application in these facilities several potential European 3D-CFCs were compared and qualified: (1) four material batches of NB31 produced by Snecma Propulsion Solide (SNECMA); (2) NB41, SNECMA, the upgraded version of NB31; (3) N31, SNECMA, which is densified by chemical vapor infiltration (CVI) instead of a final liquid pitch infiltration characteristic for NB31; (4) a new developmental 3D-CFC produced by DUNLOP.The characterization of the composites is comprised of thermo-physical measurements and tensile tests. The results are correlated to density and microstructure and summarized as follows: (1) NB41 provides the highest thermal conductivity in the ex-pitch direction of 375 W/(m K) at room temperature; (2) all material grades are, due to their heterogeneity, characterized by a relatively large scatter of mechanical properties; (3) the different densification process for N31 in comparison to NB31 has no influence on the material properties; (4) NB41 provides in all three directions a comparably high tensile strength with an average in the ex-pitch direction of 220 MPa; (5) the 3D-CFC from DUNLOP is comparable to NB41 but yet does not meet the specifications in the needling direction.     

PCS7 6．0在阿尔巴尼亚FUSHE-KRUJE水泥厂项目中的应用

本文主要介绍西门子过程控制系统PCS7 6．0在阿尔巴尼亚水泥厂DCS中的应用技术。充分展示了该系统的方便性、可靠性、灵活和稳定性，以及在做项目的过程中遇到的一些问题和解决的方法。     

CFC research programmes in Western Europe

The structure of CFC use in Western Europe is different from that in the USA and Japan, with the highest percentage use of CFCs in Europe in aerosols. The use of CFCs in automotive air conditioning in the EEC is much less than elsewhere and this, together with the fact that R-12 and R-22 already have similar market shares, means that the refrigeration industry in Western Europe will not be as greatly affected by CFC reduction as elsewhere. More stringent reduction programmes than those imposed by the Montreal Protocol are in force in most Western European countries, to some extent due to consumer and environmental pressure group influences. Some countries, especially in Scandinavia, are introducing additional legislation to restrict CFC use. The strongest stand has been taken by the Federal Republic of Germany, which requires a 95% reduction in CFC use by 1995, with a voluntary ban from 1992. This paper discusses in detail European research programmes into CFC replacements. Many projects have been proposed, including work on refrigerants [fundamentals (four projects), thermophysical properties (18 projects) and lubricants and materials (five projects)] and cycles and components (17 projects).