太阳能空调系统性能分析

本对太阳能高效平板集热器与热水型一级溴化锂吸收式制冷机及热水型两级溴化锂吸收式制冷机组成的空调系统进行了计算分析。结果表明,在热水温度为８２－９５℃的范围内,太阳能一级溴化锂吸收式制冷系统具有较高的效率,但系统效率随热源温度的下降而急剧降低;在热源温度为６５－８２℃的范围内,太阳能两级溴化锂吸收式制冷系统具有较突出的优越性,系统效率几乎不随热源温的变化而变化。因此,两级溴化锂吸收式制冷机与太阳能平反集热器有比较好的匹配性能。     

新型太阳能降压吸收式制冷空调系统特性的理论分析

在两级溴化锂吸收式制冷的基础上提出了一种新型高效的降压吸收式制冷循环,能够有效利用太阳能实现制冷,解决传统吸收式太阳能空调系统存在的弊端。其特点是在传统的两级吸收式循环的基础上,将高压发生器发生出的LiBr溶液与低压吸收器的吸收后的溶液混合,在发生温度与压力允许的范围内,使高压吸收器的吸收剂浓度较两级吸收式循环高,从而在相同的冷凝条件下减小了其压力。分析了新型空调系统的性能特性,理论计算结果表明影响新型系统整体效率的主要因素是LiBr溶液的浓度及驱动热源的可利用温差。新型吸收式循环热源可利用温差最高可达33.5℃,整体效率比两级吸收式系统有较大提高,最大提高46.4%,其集热面积单耗最大减小47.1%,热源单耗是两级系统的0.21,效果较明显。     

漫谈太阳能制冷与空调

太阳能取之不竭，用之不尽，对坏境没有污染，是一种最有前途的能源。如今，人们正在考虑利用太阳能制冷，因为在夏季太阳能最丰富的时候，也是人们最需要空调制冷的时候。利用太阳能对房间进行温度调节，首先要解决如何用太阳能制冷的问题。目前，用太阳能制冷主要有三种方法：一是吸收式制冷，即利用太阳辐射热能驱动溴化锂水溶液或氨水溶液的吸收式制冷系统：二是利用太阳能加热通过集热器内的低沸点工质，经汽化后通入汽轮机驱动制冷机制冷.[第一段]     

太阳能相变蓄热应用于吸收式制冷的研究

介绍了一种将太阳能相变蓄热技术应用于两级吸收式制冷的新型空调系统,简要分析了该系统的装置结构、工作原理和使用优点.对相变蓄热装置放热过程中放热盘管出水温度随放热时间的变化关系进行了实验测量,并对两级吸收式制冷系统效率进行了分析.通过研究可知,该太阳能空调系统有效解决了以往系统不稳定性和间断性问题;太阳能相变蓄热装置具有体积小、蓄热量大、放热速率大、连续放热温度均匀、便于控制热源加热温度等特点,适合储存太阳能并为吸收式制冷系统提供加热热源.综合考虑系统设备简单,加工要求低的制造特点,所以吸收式制冷以太阳能等低品位热源驱动有着良好的发展前景.     

香港一套太阳能驱动空调系统的性能

一种太阳能驱动吸收式空调系统在香港大学建造成功。系统由平板集热器阵列,溴化锂吸收式制冷装置、热水储存箱、冷却塔、风扇盘管装置、电辅助加热器、数据采集系统和辅助控制系统所组成。文中详尽地叙述了香港大学的太阳能空调系统,也讨论了在整个制冷季节过程中的性能并与意大利、新加坡的类似系统进行了比较。     

太阳能空调与热水综合系统

本文报导了建造在深圳市的太阳能空调及供热水综合系统的设计特点及一年来运行概况。该系统采用三种型式太阳能中温集热器,利用热水驱动溴化锂吸收式制冷机供冷,设有贮热及贮冷装置,用微处理机进行数据采集及自动控制。运行中,比较了三种集热器的性能。     

用于直接吸收式太阳能集热器的纳米流体研究进展

不同于传统的平板集热器和真空管集热器,直接吸收式太阳能集热器是一种集热工质直接吸收太阳辐射能量并转化为集热介质内能的新型集热器。从传热学角度,直接吸收式太阳能集热器因为减少了吸热表面到集热工质之间的传热损失而具有更高的集热性能。然而,传统的集热工质(如水、导热油、乙二醇等液体)对太阳光的吸收能力以及光热转换效率极其有限。近年来,纳米流体因其优异的传热性能和光学性能而被视为应用于直接吸收式太阳能集热器集热工质的最佳选择。本文介绍了直接吸收式太阳能集热器的传热模型,列举了用于直接吸收式太阳能集热器的纳米流体的研究进展,归纳总结了各类具有代表性的纳米流体及其光热转换性能的相关研究,最后对纳米流体在直接吸收式太阳能集热器中的应用进行了展望。     

低制冷量溴化锂吸收式制冷机的稳态和瞬态特性

为获得太阳能致冷,实际上使用过的只有溴化锂吸收式制冷机,它能够在平板集热器所允许的低温水平下工作。近来,为了太阳能降温的目的而制造出低制冷量的吸收式制冷机,其容量范围在5至35KW 之间,而所需的发生器温度据称低于100℃很多。太阳能冷却系统的一个固有的特点却是其瞬态特性。瞬态特性是非常难以估算的,因为这些机器通常并没有装置电动的溶液泵。溶液是     

热水型溴化锂两级吸收式制冷机在工业中的应用

３５０ｋＷ低温热水驱动的两级溴化锂吸收式制冷机已研制成功，并已连续运转５年。该机以热电厂冬季采暖管道输送的８６℃热水为热源，在冷却水温度３２℃的条件下，制取９℃冷媒水，供５０００ｍ２办公大楼空调。该机可在热源温度７０～８６℃下运行，热源出口温度为６０℃，机组的制冷系数为０．３３～０．３９。两级吸收式制冷机可在回收工业废热、太阳能、地热能等方面得到广泛的应用。     

纳米流体在直接吸收式太阳能高温集热器中的应用研究

对纳米流体应用于直接吸收式太阳能高温集热器领域的研究现状进行了整合。具体阐述了国外研究者在此方面的研究进展。偏重于纳米流体辐射特性的理论研究,通过理论计算,得到太阳能集热器的集热效率并结合一定的实验模型进行验证。并对可以应用于直接吸收式高温太阳能集热器中的几种纳米流体进行了实验对比测量,得到可供参考的结果。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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 Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.