低温试验箱隔热层传热特性的实验研究

研究了1台在给定时间内达到-30 ℃的低温型试验用小型制冷低温试验箱,该试验箱配有全自动的微机控制系统能完成各项试验的数据记录.主要针对低温箱围护结构(隔热层)在降温阶段非稳态传热特性进行了实验研究.通过试验数据分析,对隔热层在降温过程的一维大平板非稳态传热问题进行了内部温度场随时间变化关系的的讨论,同时对低温箱隔热层随时间变化的放热量进行了数据拟合并得出了简化公式,为这类有特殊要求的制冷装置在节能节材方面的设计提供了的一定的参考数据.     

复合材料包装箱保温功能设计及验证

目的为满足包装箱保温功能技术要求,探究包装箱保温层厚度设计方案。方法基于低导热系数聚氨酯保温材料,通过傅里叶定律及安全系数理论分析确定包装箱保温层厚度,再对实物包装箱按照GJB 150.4.A—2009《军用装备实验室环境试验方法》进行高低温试验并验证。结果在高低温试验中,当箱内温度为22.2℃,箱外温度为40℃时,4 h后箱内最高温度可达29.2℃;当箱内温度为25.5℃,箱外温度为?30℃时,4 h后箱内最低温度降至2℃。通过分析,得出箱体内部温度与时间以及箱体温差之间的关系,箱体外部升温1℃时,箱体内部升温速率为0.037~0.1℃/h;箱体外部降温1℃时,降温速率为0.07~0.094℃/h。结论该设计方案能满足包装箱保温功能技术要求。     

基于热力学排气的液氮贮箱控压技术研究（英文）

液氢、液氧等低温推进剂在漏热影响下在轨贮箱压力将逐渐升高,采用热力学排气技术的低温贮箱在常重力环境下开展了压力控制原理验证试验,在对试验系统及热力学排气原理进行分析的基础上,贮箱内压力和液相温度随着时间的变化曲线在混合和并行模式中分别给出,测试结果显示在混合模式中单次控压循环时间逐渐缩短,而在并行模式中随试验开展时间逐渐增加,与混合模式阶段相比,液相温度的上升速率明显降低,验证了热力学排气在控制低温贮箱压力方面的效能。     

复叠式空气源热泵热水器结霜工况下的机组运行参数研究

复叠式空气源热泵热水器可以在冬季低温(-25℃)下最高提供80℃热水,但是机组结霜问题对机组的效率和供热性能影响较大。通过研究复叠式热泵热水器的结霜规律以及结霜对机组性能的影响,为进一步研究并优化除霜控制方法提供依据。系统分为低温级循环和高温级循环,低温级循环为室外系统,高温级循环及蒸发冷凝器部分为室内系统,热泵循环低温级采用R410A作为循环工质,高温级采用R134a,热泵系统高温级冷凝温度为80℃,低温级的蒸发温度可达-40℃。通过在焓差实验室实验进行研究。测试复叠式热泵的结霜过程时间与结霜量,得到不同室外温湿度与结霜量之间的关系。结霜量通过测量低温级蒸发器进出口含湿量的方法获得,并分析结霜对于机组实际耗电量以及COP等性能参数的影响。     

不同降温速率对肾细胞内、外冰形成温度的影响

分别采用低温显微镜和差示扫描量热仪测定胞内冰和胞外冰的形成温度,分析了胞内、外冰晶产生温度和降温速率的关系,并通过低温显微镜获得了降温过程中肾细胞形态的变化。由实验结果可知:在降温速率小于10℃/min的情况下,肾细胞内鲜有冰晶的产生,并且降温速率升高导致胞内冰形成温度的降低。     

基于温差发电技术的节能环保燃气灶的研制

目的:探讨节能环保燃气灶研制及应用。方法:将双灶头燃气灶的一侧按照节能环保燃气灶的设计方案改造,在两侧灶具内加入等重的水,加热相同时间。间隔30s记录两灶具水温、节能环内、外水箱温度、电流、电压。结果:普通燃气灶具内水温总和:7319.5℃,节能环保燃气灶具内水温总和:7592.9℃,二者总温差:273.4℃。节能环内水箱温度总和:7217.1℃;外水箱温度总和:5044℃,二者温差:2173.1℃;总电流:5.2021A,总电压:64.6515V,发电总量:0.00003121k Wh。结论:节能环保燃气灶具有升温快、降温慢、热能利用率高、节能、环保、安全等特点。     

90K低温下带预冷的林德制冷机的系统设计

为了获得90K的低温,提出1套带预冷循环的林德制冷系统,并分别对该系统的预冷循环和制冷循环进行了设计.预冷系统和制冷循环的制冷剂分别为R404A 和 R740.无热负荷时,设定低温箱的温度90 K,制冷量为140 W.该系统整体结构简单,获取温度低,在低温领域有较广泛的应用.     

空气源热泵除霜性能测试系统设计

为实现空气源热泵产品除霜性能测试工况的低温高湿环境，设计一种长期低温运行设备及其温度耦合控制系统，通过2套制冷系统的除霜模式与制冷模式的交替循环，解决因蒸发器结霜而导致制冷量下降问题。基于实际测试系统和研究，提出切入除霜、除霜结束的判定依据：电加热输出为零且环境测试间内干球温度高于设定值0.1℃作为切入除霜判定依据；在除霜过程中，蒸发器制冷剂出口温度高于环境测试间干球温度10℃,且蒸发器空气侧阻力小于150 Pa作为除霜结束判定依据。该方案能够解决环境测试间内因空气处理机组蒸发器除霜需求而造成的干球温度和相对湿度的剧烈波动问题，保证环境测试间内低温高湿环境工况的长期稳定，提高除霜工况的测试准确性。     

基于减压降温原理的过冷液氮冷却系统研制

随着超导技术的迅速发展,为超导材料提供低温环境的制冷系统得到了越来越多的关注。本文详细介绍了一种基于减压降温原理的高温超导电机过冷氮冷却系统,包括技术指标及相关要求、总体结构、关键技术、热负荷分析与计算等。系统采用减压降温获得过冷液氮,冷却电机中超导线圈。液氮进口温度68K,出口温度72K。主要由供液杜瓦、过冷箱、抽空泵、超导线圈杜瓦、返液杜瓦、低温管路及温度仪表组成。试验证明,该冷却系统设计合理、操作方便,成功实现了超导电机的加载运行。     

用于生物材料低温保存的一种新的冷却技术

许多生物材料的低温保存,要求在0℃至-40℃的这段危险区内保持匀速降温,而且希望能缩短相变阶段的时间。本文分析了用程序控制降温仪或用“两步法”这二种冷却技术所存在的问题,提出了一种全新的冷却技术,这就是用浸有盐水或酒精等溶液的纱布包裹在盛生物材料的塑料袋外,然后直接放入-60℃低温箱中,经过一段时间后再放到液氮中。这种新技术不仅能使生物材料均匀降温,而且可以明显地缩短相变阶段的时间,达到了很好的低温保存效果。本文还运用传热学理论建立了该技术的物理——数学模型,并给出了对实用有指导意义的分析。     

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.     

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...     

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.     

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.     

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