超临界CO2循环冷端温度优化研究

超临界CO₂循环冷端排出的热量温度较高,优化冷端温度对于提高循环的效率有重要作用。为了获得最佳的全年平均效率,有必要引入人工制冷,使超临界CO₂循环运行在更优化的冷端温度下。针对550℃/20 MPa参数的分流再压缩方式的超临界CO₂循环,通过热力学方法,分析了自然冷却和人工制冷组合条件下,冷端温度为5~35℃的不同工况下全年平均循环效率,并对冷端温度优化方法的适用性和经济性进行了研究。选取优化的冷端温度,将自然冷却和人工制冷相结合,可提高机组的全年平均效率。对于我国北方地区,冷端温度优化方法有较佳的适用性。引入人工制冷导致机组设备投资增加,但是机组运行效率的提高带来更多的发电收入,并在机组全寿期产生可观的收入增量。     

二氧化碳复叠式制冷系统实验研究

本研究提出了一种基于CO₂固气两相升华流动的复叠式制冷系统。系统采用环保的天然工质CO₂作为冷媒。复叠式制冷系统由高温循环（HTC:High Temperature Cycle）和低温循环（LTC:Low TemperatureCycle）二个部分构成。两部分用一个中间换热器相连接。本文提出CO₂两级复叠式循环概念并进行了实验测试,利用CO₂固气两相升华流动潜热潜力,可以同时实现低于-56.6℃的制冷和80℃以上的制热。通过实验和理论计算,两级系统成功地同时实现了以上功能。此外,本文还总结了基本实验特性并做了相应的系统优化设计和分析。     

一种新型CO2工质冷热电联供系统的热力性分析

为了开发利用太阳能、地热能、工业余热等低品位热能,提出一种以CO₂作为工质的冷热电联供系统,该系统通过共用气体冷却器的方式将超临界CO₂布雷顿发电循环和跨临界CO₂压缩式制冷循环进行耦合,可同时向用户提供电力、冷媒水和生活热水。建立了该系统的热力学数学模型,并对其运行工况进行了数值模拟,模拟结果表明:系统净输出功为140.34 kW,制冷量为340.50 kW,制热量为5 332.75 kW,热效率为113.27%,?效率为41.24%;随后在此基础上对系统进行了热力学参数敏感性分析,获得了透平进口压力、透平出口压力、透平进口温度、蒸发器压力和顶循环与底循环CO₂流量比5个热力参数对系统性能的影响。     

PMMA纳米孔泡沫的制备及发泡性能研究

选用对于超临界CO₂具有高吸附能力的聚甲基丙烯酸酯(PMMA)作为基体材料,通过超临界CO₂间歇式发泡法,探究饱和阶段、发泡阶段参数以及CO₂吸附率对PMMA泡沫结构参数的影响。结果表明,在一定范围内,当其他条件相同时,降低温度或增大压力均能增加CO₂吸附率,在0 ℃、15 MPa条件下饱和48 h,PMMA中的CO₂吸附率达到最大值35.72%。将CO₂吸附率为35.72%的PMMA在40 ℃油浴中发泡30 s,可以获得泡孔密度为1.57×10¹⁵ 个/cm³、泡孔平均尺寸为35.9 nm且分布均匀的PMMA纳米孔泡沫。     

多级孔Ti-MOFs负载超细Pd纳米颗粒实现高效光热CO2还原(英文)

设计钛基金属有机骨架(MOF)实现高效光催化CO₂还原具有重要意义但仍极具挑战.本文发展了一种新的一步原位水蚀刻方法制备超细Pd纳米颗粒/多级孔Ti-MOFs高效光催化剂,其中水刻蚀在形成多级孔结构的同时也为Pd的锚定提供了丰富位点,进而在光还原的作用下一步实现Pd纳米颗粒在MOFs表面和内部的负载.得益于多级孔结构和超细Pd颗粒负载,Pd/hMUV-10在350℃光照下的CO产率高达65.9 mmol g^-1 h^-1,比目前最先进的MOF基催化剂高出约两个数量级,并超过大多数已报道的无机半导体基催化剂.在200℃相对温和的条件下,CO的产率也达到3.36 mmol g^-1 h^-1.在350℃的连续循环测试中,催化剂活性几乎没有衰减.理论计算表明,Pd负载可增强对CO₂的吸附和降低CO₂还原能垒,从而实现高效光热CO₂还原.本文所报道的Pd/hMUV-10催化剂有望在工业CO₂捕获和转化中得...     

跨临界CO2制冷技术发展现状及其改进途径综述

跨临界CO₂制冷是一种以CO₂作为制冷剂气体冷却过程在临界点以上的新型制冷技术。对近年来CO₂制冷技术的发展进行了概括及分析。针对传统制冷剂与CO₂制冷剂的特点,重点分析了二者在物理性质上的区别,说明了CO₂作为新型制冷剂的可取性;针对提升制冷系数的目标,讨论了两级压缩、膨胀机、回热器的工作原理以及对系统性能的影响。综述了新型双级压缩CO₂制冷循环的研究现状,归纳了CO₂制冷循环进一步改善性能的技术途径。     

DBD转化CO2的研究现状及进展

为了更高效地进行CO₂的转化利用,许多学者开展了多种CO₂转化方法的研究。介电阻挡放电（dielectric barrier discharge,DBD）能在低温常压的环境下还原CO₂,是CO₂转化利用的重要方法之一。为了设计出更好的DBD反应器、更佳的反应条件和催化剂,总结了近年来DBD转化CO₂的相关研究。通过分析不同研究中过程参数、稀释性气体和催化剂等因素对CO₂转化量和能量效率的影响,发现催化剂能大幅度提高DBD转化CO₂的反应效率,并介绍了DBD中一些常用的催化剂。最后简要分析了此类研究的可能发展趋势。     

面向灵活性发电的燃煤机组大气排放特性分析

随着可再生能源发电在电网中占比逐年增加,越来越多的燃煤机组参与灵活性发电。为了弄清灵活性发电燃煤机组的大气排放特性,以某亚临界600 MW和300 MW机组为例,通过对运行数据进行回归分析,获得了机组在启动、正常调峰和深度调峰阶段的CO₂、NO_x、SO₂和粉尘的排放特性。结果表明：正常调峰阶段,随着机组负荷下降,煤耗和CO₂排放因子逐渐增大,净烟气NO_x排放因子先减小后增大,SO₂排放因子略有下降;粉尘排放因子略有上升;深度调峰阶段,随机组负荷的进一步降低煤耗和CO₂排放因子明显增大,净烟气NO_x和粉尘排放因子迅速增大,SO₂排放因子继续下降;启动过程净烟气NO_x和粉尘排放因子明显高于调峰工况,SO₂排放因子略小于调峰工况。另外,调峰过程中较高的升降负荷率使得原烟气NO_x、SO₂排放因子明显增大,净烟气粉尘排放因子明显增大。     

新能源车用CO2空调系统泄漏特性仿真研究

CO₂作为一种安全、高效且环境友好的自然工质,是未来汽车空调制冷剂替代方案的重要选择。考虑到CO₂系统制冷剂泄漏导致乘员舱气体体积分数超标的舒适及安全问题,本文使用三维仿真软件STAR-CCM+搭建乘员舱CO₂制冷剂泄漏仿真模型,仿真分析两种不同泄漏速率和泄漏圆孔孔径下乘员舱乘客面部测点CO₂体积分数的动态变化情况。在50 g/s的高CO₂泄漏速率下,面部CO₂体积分数在泄漏完成时能够达到9%以上,需要切换送风模式提供新风来降低乘员舱内CO₂体积分数;在0.1 g/s的低CO₂泄漏速率下,泄漏完成时面部CO₂体积分数不超过3%,处于呼吸安全区范围。     

CO2热泵系统气冷器的热力学性能分析

针对CO₂热泵系统螺旋套管式气冷器,基于MATLAB建立了仿真模型,采用单因素分析方法,研究进水温度、CO₂压力和质量流量对气冷器换热量、■耗散、■损失、■效率以及出水温度的影响。经实验验证,在进水温度为24.5～35.0℃、CO₂压力为8.4～10.7 MPa、CO₂质量流量为0.032 6～0.047 6 kg/s工况下,气冷器模型制热量与实验数据相比总体误差在±10%以内。模拟结果表明：相比进水温度和CO₂质量流量,CO₂压力对气冷器性能的影响更为显著,且存在最优压力。在进水温度为20℃、CO₂进口温度为90℃工况下,当CO₂压力为10 MPa时气冷器■效率最高,当CO₂压力为11 MPa时气冷器换热量最大;当进水温度低于20℃时,CO₂压力为10.5 MPa时出水温度最高。     

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.     

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.     

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.……     

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...     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

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.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...