An analysis of the heat transfer rate and efficiency of TE (thermoelectric) cooling systems

The heat transfer rate and efficiency of TE (thermoelectric) cooling systems were investigated. The emphasis of the present study is focused on the use of large-scale TE refrigerators for air conditioning applications. A one-dimensional heat transfer analysis was performed to determine the cooling power and electricity consumption of the TE elements. The constant-property results are in good agreement with the variable-property solutions for TE materials and temperatures typical for air conditioning applications. A heat transfer analysis was also carried out for TE refrigerators equipped with a heat exchanger. Both parallel- and counter-flow heat exchangers were considered. Fluid temperature variations of these two flow arrangements were found to be quite different, but the efficiencies and cold fluid exit temperatures differed only slightly when a uniform current was used for all TE elements. If the length of the heat exchanger exceeds an optimal value, the cold fluid temperature begins to rise and the efficiency drops for both parallel- and counter-flow arrangements. The second law of thermodynamics was applied to the optimization of TE refrigerators operating between two constant-temperature reservoirs and between two flowing fluids. It was found that if a TE cooling system incorporates a heat exchanger, a nonuniform current distribution should be used to achieve the maximum efficiency and the lowest cold fluid temperature. The optimization results for TE refrigerators operating between two constant-temperature reservoirs are not applicable to TE cooling systems between two flowing fluids. The most energy-efficient current distribution for the parallel-flow arrangement is the one which increase in the direction of the cold fluid.     

基于网络理论的固伴火箭发动机纤维缠绕壳体优化设计

基于网络理论按爆破压强设计的纤维缠绕壳体基本方程,在结构、工艺等约束条件下,选取不同纤维材料,以壳体质量为目标,利用线性多步法和复合形法,优化设计纵向层平面缠绕、圆筒部分在环向缠绕的固体发动机纤维壳体的材料密度、纤维拉伸强度、缠绕角和极孔半径,并给出算例。计算表明,比强度是影响纤维壳体质量的最重要因素。     

基于本体的网络数据工作平台NetData

近年来,网格、语义网络等新技术迅速发展并日臻成熟。互联网发展焦点开始从信息的发布和互联转向知识的交互框架。随着语义网络迅速发展,世界各地各个领域的研究爱好者组成虚拟社区,对同一领域的知识信息一起协作研究。其中,对数据的整理、保存、检索、分析是实现语义网络远景的基础工作。本文为了帮助研究社区的研究人员更有效方便地加入社区的研究,利用长期帮助中国中医研究院建设专业结构化数据库群的项目中所取得的经验,结合了语义网络和数据库网格的研究,设计并初步实现了基于本体的网络数据工作平台。     

影响草毒果汁红色素变化的因子研究

通过试验对草莓果汁在加工及继后贮藏过程中,影响红色素变化的因子进行了研究。结果表明,迅速加热果实温度到60℃,有利于提高果汁中红色素含量;向果汁中分别加入0.1%~0.4%的抗坏血酸、酒石酸和柠檬酸对果汁具有明显的增色作用;而加入1.0%~15.0%的葡萄糖和蔗糖对果汁颜色没有影响;调整果汁pH值到4.0以下有助于保持果汁的固有颜色;采用低温避光贮存果汁可延缓草莓果汁红色素的降解。     

用AT91RM9200构建高可靠嵌入式系统

提出一种基于AT91RM9200处理器的高可靠双机温备解决方案.利用EP1C6、MAX6374设计两个冗余的外部Watchdog监控处理器系统的工作状态,利用AT91RM9200自带的Watchdog作为内部监测机制监控处理器本身的故障;设计并给出了以AT91RM9200为核心的监控机制的具体实现,包括心跳信号的发送和中断服务程序的设计.     

基于X3D的远程教育系统的设计与实现

远程教育作为一种独立的教育形态,已经从第一代的函授教育发展到现在的以网络教育为主要的形式的现代远程教育阶段。2004年,国际标准化组织通过X3D规范,从此X3D成为网络3D的标准。本文把X3D引入到远程教育系统的设计与实现当中,设计了基于X3D的远程教育系统,并对实现这个系统的关键技术和实现的过程做了详细的探讨。     

山东招远大尹格庄3000 m科学钻探施工技术

山东招远大尹格庄3000 m科学钻探项目是在胶东地区招平断裂带处施工的最深科学钻探项目,设计钻孔深度为3000 m。为达到提高钻探施工效率、降低孔内事故概率的目的,本项目采用高效稳定的XY-9DB型变频钻机、自主研发的高效长寿命金刚石钻头、CHD76系列高强度钻杆及联合研发的LZRT360型钻井液离心机,采用了P/H绳索取心液动冲击钻探技术、绳索取心涂层减阻内管技术等关键技术,进行深孔钻进施工,并针对不同地层进行了冲洗液体系的优选。该项目终孔孔深3120.35 m,终孔孔径78 mm,平均岩心采取率95.6%,平均矿心采取率97.9%。本文对此项目施工过程中钻遇复杂地层的处理方法、解决方案以及设备使用情况进行了总结,为类似深部钻探工程项目提供了参考。     

GaN-based Indium-tin-oxide light emitting diodes with nanostructured silicon upper contacts

GaN-based indium-tin-oxide (ITO) light emitting diodes (LEDs) with p-GaN, n⁺-short period superlattice (SPS) and nanostructured silicon contact layers were fabricated. It was found that surface of the ITO LED with nanostructured silicon layer was very rough. It was also found that 20 mA forward voltages measured from ITO LEDs with p-GaN, n⁺-SPS and nanostructured silicon contact layers were 6.01, 3.25 and 3.26 V, respectively. Compared with ITO LED with n⁺-SPS, it was found that output power of ITO LED with nanostructured silicon contact was 17% larger. Furthermore, it was found that ITO LED with nanostructured silicon contact was more reliable.     

叶绿素铜钠盐吸附羊毛织物的动力学研究

基于能上染绿色的天然染料很少,文章研究了叶绿素铜钠盐吸附羊毛织物的动力学过程。研究表明,在70～100℃染色温度范围内,叶绿素铜钠盐在染色初期上染羊毛速率很高,随着染色时间增加到20 min后,上染速率降低,60 min后上染百分率、织物上的染料量基本不变,上染达到平衡;叶绿素铜钠盐染后羊毛织物的颜色特征值表观深度与时间的关系与上染百分率趋势基本一致,当染色时间达到120 min后,织物K/S值不再随时间增加而提高;随着染色温度的提高,叶绿素铜钠盐上染羊毛的平衡上染百分率提高,扩散系数提高;准二级动力学模型能很好地描述叶绿素铜钠盐染羊毛织物的染色动力学,该吸附过程以化学吸附为主。