变温热源不可逆布雷顿制冷循环制冷率和制冷系数优化

用有限时间热力学方法分析变温热源不可逆简单布雷顿制冷循环的特性,分别以制冷率和制冷系数为优化目标,优化了循环中换热器的热导分配以及工质和热源间的热容率匹配,并采用数值计算分析了压比、换热器总热导、压缩机和膨胀机效率、工质热容率等参数对最优制冷率和制冷系数的影响特点.所得结果对工程制冷系统设计有一定的指导意义.     

不可逆四热源制冷循环的优化性能

研究传热遵从线性唯象律的不可逆四热源制冷循环的优化性能,导出循环的基本优化关系和最大制冷率及其相应的制冷系数.揭示了四热源制冷循环等效于一个三热源制冷循环,而且还可使四热源制冷循环转化为一个三热源制冷循环而获得更优的制冷效果.     

不可逆联合制冷循环的重要设计参数

建立一类存在热阻，热漏和内部耗散的定常流态联合制冷机循环模型，并研究其性能优化，导出制冷系数，制冷率基本优化关系和最大制冷系数及其相应的制冷率，给出了传热面积的最佳值工质最佳工作温度。所得结果适用于由任意个制冷机串接而成的联合制冷循环。     

广义三热源制冷循环的等效联合系统

首先将工作在有限高温热源和两个恒温热源之间的一类广义三热源制冷循环抽象为一个广义卡诺热机驱动一个卡诺制冷机的等效联合系统,然后应用广义卡诺热机和卡诺制冷机的有限时间热力学理论,导出广义三热源制冷循环在不可逆传热情况下的最佳制冷系数与制冷率间的关系。由此讨论这类制冷循环的各种优化性能,并给出这类制冷循环在几种特殊情况下的等效联合系统。所得的结果可为吸收式制冷机、喷射式制冷机和化学热泵等制冷设备的进一步开发和利用提供参考依据。     

联合制冷循环的优化分析

基于有限时间热力学理论,分析由两个内可逆卡诺制冷循环构成的联合制冷循环的优化性能。首先导出联合循环的制冷率与制冷系数的普遍关系，再由它求出活塞式和定常态流两种联合制冷循环在不同约束条件下的基本优化关系，并作了些有意义的讨论，获得一些对实际联合制冷循环有参考价值的新结论，同时还澄清了有关研究中存在的一些问题。     

回热式布雷顿制冷循环的性能优化

基于回热式不可逆布雷顿制冷循环模型，导出循环的制冷率、性能系数和输入功率等一些重要性能参数的一般表达式及制冷率和性能系数之间优化关系所满足的方程，研究回热和各种不可逆性对其优化性能的影响，讨论了循环的优化运行区间及其性能界限，确定了最佳传热面积。通过数值计算分析了设计参数对循环的制冷率、性能系数和输入功率的影响。     

磁埃里克森制冷循环

对磁埃里克森制冷循环作了简要的讨论和介绍.指出磁埃里克森制冷循环不具有理想(完全)的热,其制冷系数低于同样温度的卡诺制冷循环的制冷系数.但磁埃里克森制冷循环仍是磁制冷机研制中值得重视的一种循环方式.可存磁制冷技术劈展中起重要作用.     

回热式空气制冷循环的有限时间热力学分析

导出存在热阻和不可逆压缩、膨胀损失的恒温热源回热式空气制冷循环的制冷率和制冷系数与循环压比间的解析式。     

空气制冷机制冷系数影响因素的分析

通过对空气制冷机理论循环、实际循环制冷系数的分析 ,指出了影响其制冷系数的因素 ,并探讨了提高空气制冷机效率的途径 ;同时也对空气制冷机用于空调领域的一种可能的制冷循环进行了分析 ,指出了提高其制冷系数的可靠途径     

不可逆布雷顿制冷循环的性能优化

基于不可逆布雷顿制冷循环模型,导出循环制冷率和性能系数之间优化关系所应满足的方程,利用数值解,研究内不可逆性和传热不可逆性对优化性能的影响.讨论了循环的各种优化性能,所得结果对实际制冷系统的优化设计有一定的指导意义.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.