基于铀的激光氮化机理研究和数值模拟

针对工件铀的表面激光氮化工艺,考虑铀的固-液相变过程中各物理参数随温度的变化,结合计算流体软件FLUENT中流体体积函数(VOF)模型计算气-液相界面处的降膜解吸传质过程。进行了铀的瞬态激光氮化传热传质耦合数值仿真,仿真分析研究了不同工艺参数下瞬态温度场和流场的分布,同时获得渗氮量在铀表面和深度上的分布。分析结果表明,因激光局部加热引起的表面张力梯度导致的Marangoni对流对铀表面氮化过程中的传热和传质有很大的影响。其中渗氮量在不同工艺参数下的数值结果与试验结果相吻合,验证了数值模型的可行性,为激光氮化的理论分析和工艺指导提供了理论和方法。     

激光熔丝增材过程传热流动行为数值模拟

目的 研究激光熔丝增材制造过程的熔池流动特性,探究工艺参数对熔池流动与传热行为的影响.方法 建立了考虑运动丝材持续送进过程的激光熔丝增材熔池传热和流动行为数学模型.针对316L不锈钢的激光熔丝增材制造,开展了成形过程中丝材送进、熔化和凝固行为的实验和数值模拟研究.结果 模拟结果 显示在成形过程中,准稳态阶段激光辐照中心...     

横荡工况下板翅式换热器内天然气冷凝特性的模拟研究

为了定量描述海上横荡工况对板翅式换热器内天然气冷凝过程热质传递的影响规律,建立了板翅式换热器波纹翅片通道内冷凝流动与传热的数值模型。首先针对天然气冷凝过程的传热传质机理进行分析;通过翅片壁面的组分守恒建立了天然气冷凝过程的传质子模型,并基于传质速率计算得出潜热传热速率。基于提出的模型,对于不同干度下的板翅式换热器内天然气传热传质进行分析,发现当干度为0.05时,传热系数平均恶化32.9%,当干度上升至0.2时,恶化得到改善,传热系数平均降低28.7%。     

波纹翅片通道内液化天然气流动沸腾换热特性分析

波纹翅片广泛应用于液化天然气板翅式换热器中;为了对板翅式换热器进行优化设计,必须明确翅片通道内的流动沸腾机理。首先对波纹翅片流道中流体的流动和传热传质机理进行分析,建立了稳态工况下汽化相变模型。然后进行了不同质流密度、热流密度和干度工况下波纹翅片流道内流体流动换热过程的模拟,分析了质流密度、热流密度和干度对波纹翅片传热特性的影响,并与平直翅片进行了对比。结果显示:随着干度增大,波纹翅片换热系数呈现先上升后下降的趋势,且在0.5干度左右达到最大值;随着干度增加,质流密度的增大对换热性能的提升越来越明显,热流密度的增大对换热性能的提升越来越小;波纹翅片比平直翅片换热系数提高30%~150%,在低干度工况下波纹翅片强化传热效果更明显。     

40Cr轴面激光熔覆Ni60数值模拟

目的 针对激光熔覆过程中熔池内部复杂的传热和对流现象,分析激光功率和扫描速度对熔池内部温度场、流场演变和分布的影响.方法 采用双椭球热源模型,建立了40Cr轴面基体激光熔覆Ni60粉末过程的三维温度场流场数值模型,并进行试验验证.结果 熔覆过程形成了近似椭球体的熔池,最高温度位于移动光斑中心偏后方,达到了2080.4 ...     

载银二氧化钛纳米流体强化气液传热传质实验研究

在碳中和背景下,减少能源消耗、提高暖通运行能效和净化效率是在新时代亟需解决的问题。本文研究了载银二氧化钛(TiO₂-Ag)纳米流体的气液传热传质性能,探索了纳米流体在鼓泡、喷雾、填料等不同流动状态下的传热传质特性,分析了系统参数对传热传质效果的影响。结果表明：鼓泡工况相对于喷雾与填料工况的气液传热效果更好,其中气体流量的设定应同时考虑纳米流体稳定性和气液接触时间等因素来获得最佳效果,因此在本实验的设定中,选定最佳进口气体流量为4 L/min。     

化学吸附式制冷系统传热传质的数值模拟和实验研究

运用多孔介质理论分析了化学吸附式制冷系统中的吸附床，按多孔介质的质量、动量和能量传递过程建立了吸附床内流动、传热和传质耦合求解的数学模型，并根据吸附剂在吸附床内多孔介质中的流动特性，采用比经典的Darcy模型更精确的多孔介质流动模型-Ergun模型。所建立的数学模型较之现有的吸附床传热传质数学模型能更全面、准确的描述吸附床的传热传质特性。将所建立的模型对化学吸附制冷样机进行了模拟计算，计算结果和测试结果吻合得较好。数学模型和计算结果有助于深入认识吸附床的传热传质特性，并可进一步用于吸附床和系统的优化设计。     

TC4合金空心阴极真空焊接熔池动态行为的数值模拟

建立了空心阴极真空电弧焊(Hollow Cathode Vacuum Arc Welding, HCVAW)焊接TC4钛合金板(5mm厚)熔池中流体流动和传热过程动态行为的物理、数学模型,并对焊接过程进行了数值模拟计算和工艺试验、通过计算,找出了焊接速度和焊接电流等工艺参数对焊缝成型的影响规律,并计算出焊接过程中工件上的温度场分布和熔池中的流场分布,计算结果与实验结果基本相符.     

TG合金空心阴极真空焊接熔池动态行为的数值模拟

建立了空心阴极真空电弧焊（Hollow Cathoda Vacuun Arc Welding,HCVAW)焊接TC4钛合金板（5mm)熔池中流体流动和传热过程动态行为的物理,数学模型,并对焊接过程进行了数值模拟计算和工艺试验,通过计算,找出了爆接速度和爆接电流等工艺参数对爆缝成型的影响规律,并计算出焊接过程中工作上的温度场分布和熔池中的流场分布,计算结果与实验结果基本相符。     

湿工况下翅片管换热器空气侧热质传递动态模拟

析湿在翅片管换热器用作蒸发器时经常发生,对换热器的性能有重要影响。本文提出了能动态描述翅片管换热器空气侧析湿过程的数值模型,该模型不仅包括析湿过程中的传热传质模型,而且包括描述冷凝水滴形状和流动的运动模型。数值模型的计算精度较好,传热无量纲参数j_h和实验数据的平均相对误差为6.93%,传质无量纲参数j_m和实验数据的平均相对误差为12.1%。结果表明:该模型能准确描述翅片管空气侧析湿过程。     

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.……     

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.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to     

Win-Win Cooperation

正The Chinese Premier Li Keqiang's recent trip to the UK has reinforced the China-UK comprehensive strategic partnership;just as the British Prime Minister David Cameron put it,"the relationship is gaining in strength,depth and understanding"after a bucket of business deals being inked worth more than 30 billion US dollars.From the first agreement signing in 2004 to the new agreement of mutual standards recognition and adoption in     

Systematic Approach for Emerging Industry

正A national directory of standards complexes for strategic emerging sectors was recently developed and released jointly by 12governmental departments,namely,SAC,NDRC,MOST,MIIT,MEP,MOA,AQSIQ,State Forest Administration,State Administration of Science and Technology for National Defense,State Oceanic Administration and National Railway Administration.     

Strictest Pollutants Emission Standards

正Four new national standards on air pollutant emission control offi cially issued by the Ministry of Environment Protection(MEP)together with AQSIQ and SAC has been brought into force from July 1,2014.The Emission standard for air pollutants of coal-burning,oil-burning and gasfi red boilers,which is the strictest emission standard historically,will tackle the stubborn pollution problem of boilers and waste incineration in most of China’s regions.     

Instructions to Authors

New Carbon Materials is a bimonthly journal published with the permission of the Ministry of Science and Technology and of the State News and Publication Agency.The journal is sponsored by the Institute of Coal Chemistry,Chinese Academy of Sciences,and is published by Science Press.Aims and Scope     

Progress on Standards Copyright Protection

正Recently,National Copyright Administration of China(NCAC)has rewarded 215 organizations and 179 individuals for their outstanding efforts on investigating standards copyright infringement and piracy in 2013.Hua Jianhua,the Deputy-Director of National Standards Copyright Protection Workgroup Office won a third prize of the national individual award.In 2012,SAC set up the national standards copyright protection working group,and developed policies to crack down standards infringement and piracy behaviors and to strengthen standards copyright protection.