基于非稳态RANS模型的冷库库门渗风研究

伴随冷库总量的快速增长,冷库的能耗问题已越来越受到关注。库门渗风作为冷库的一项占比很大的热负荷是冷库能耗研究的一个重点。本文采用非稳态RANS模型对库门渗风建立了动态模拟模型,利用对一座库高和门高之比为2:1的冷库不同库内外温差和冷风机运行模式下的实测数据进行验证,结果表明：所建模型预测的渗风量、测量点当地风速和温度的数值和变化趋势都与实验值有较好的吻合,在开门时间40 s内渗风量模拟误差在±10%以内。利用该模型对渗风的特性和机理进行了模拟分析,结果表明,受风机水平方向风场影响,风机开时库内温度均比风机关时低。库内外空气密度差较小,库内冷空气受重力的影响不大,因此渗风量随开门时间呈线性变化。     

冷链运输装备渗风模型构建与实验研究

冷链运输装备渗风直接影响运输安全与能耗,但是有的冷链运输装备标准采用压差法所测得的渗风量值难以表征车辆运行时的实际状况。针对这一问题,对冷链运输装备的渗风机制进行分析,得到渗风量与装备运行速度、老化状况、装备状况的相互关系,推导并得到冷链运输装备渗风计算模型,在实验基础上得到渗风指数、当量渗风面积等相关参数的确定方法。研究表明上述模型能较好的反映冷藏运输装备渗风特性,可为冷藏车气密性状况的整体评价和优化控制提供参考。     

液态法制备金属基复合材料浸渗动力学模型的研究进展

液态制备法因具有成本低、工艺简单和可操作性强等特点而广泛应用于金属基复合材料的工业化生产。其中,液态浸渗法制备复合材料的关键在于浸渗过程,因此如何控制浸渗过程中的工艺参数来制造高质量的复合材料是人们一直关注的课题。综述了液态法制备金属基复合材料的浸渗动力学模型研究现状,分析了当前研究中存在的问题,提出了相关建议,展望了复合材料浸渗动力学模型的发展趋势。     

长期风荷载作用下冷却塔失效分析的数学模型

本文基于广义样条子域法，在合理构造冷却域计算模型的基础上，建立了研究长期风荷载作用下冷却失效机理分析的数学模型。该模型采用矩阵逆摄动法考虑长期风荷载作用下冷却塔的失效过程。并通过引入一个“区域失效系数”来判断各区域的失效程度，为冷却塔在长期风荷载作用下的失峁机理分析奠定了理论基础。     

岩石爆破的逾渗模型

本文在分析几种典型的岩石爆破损伤模型的基础上，发现岩石爆破损伤演化具有明显的逾渗效应。采用逾渗来描述岩石爆破损伤断裂这一动态过程是可行的，并提出了进一步可能的研究途径。     

纯镁材表面Zn，Al混合粉合金扩渗层形成的机制

根据纯镁材在扩渗温度不变的条件下,扩渗合金层形成特征随着扩渗时间的变化.研究了纯镁表面扩渗(Zn,Al)合金层的形成机制.结果表明:扩渗温度在390℃时,表面合金化过程中反应扩渗机理是镁表面合金化过程的关键阶段;扩渗时间由4 h延长至8 h,开始形成Al6Mg10Zn金属间化合物反应层,随后进一步发展为更加稳定的Al5Mg11Zn4金属间化合物.Zn元素的扩渗量对Al6Mg10Zn和Al5Mg11Zn4的转换起主控作用,并建立了相应的扩渗合金化模型.     

双层辉光离子渗金属渗入机理的研究

本文从理论上分析了双层辉光离子渗金属的溅射问题及渗入机理，提出了四种渗入模型。     

涂渗剂空心阴极放电离子渗硼的研究

本文对涂有相同渗硼膏剂的试样，分别采用空气炉、真空炉及真空空心阴极放电加热这三种不同的方法，进行了渗硼试验研究，初步得出２小时保温时间以下，空心阴极放电加热法渗速明显大于其余两种，并从物理及化学方面探讨了渗速提高的原因。     

碳钢与不锈钢表面高浓度渗铬法

在氩气气氛下，应用固体渗铬填料法对碳钢、不锈钢作了表面高铬浓度的渗铬处理，探讨了渗铬温度、时间和渗铬组分对渗层表面铬含量、厚度，试样增重和物相组分影响，碳钢、不锈钢的表面渗铬浓度分别达８０－９４ｗｔ％和７０－８２ｗｔ％。     

钢的硼—铬—稀土洪参层脆性行为研究

研究的钢的Ｂ－Ｃｒ－ＲＥ共渗层和渗硼层的脆性行为，表明，Ｂ－Ｃｒ－ＲＥ共渗层脆性明显低于渗硼层，且沿渗层不同深度的脆性分布呈“浴盆”型。进行适当渗后热处理可以降低渗层脆性。同时，地铬及稀土元素降低渗层脆性的机理作了探讨 。     

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.……     

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.     

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 ...     

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.