HFCs混合制冷剂热力性质的研究

为了利用PR方程和Huron-Vidal混合规则对三元混合制冷剂的热力性质进行精确计算,通过对10组二元HFCs混合制冷剂的汽液相平衡实验数据进行热力学关联,得出了相应的NRTL模型参数,由优选得到的过量Gibbs自由能NRTL模型的相互作用系数预测了构成R407C和R404A的三元混合制冷剂R32／R125／R134a以及R125／R143a／R134a的汽液相平衡,结果表明,泡点压力实验值和计算值的算术平均相对偏差小于0．42％,各组分的汽相组成实验值和计算值基本吻合。最后还应用相关热力性质分别对R32／R125和R407C进行了理论制冷循环分析计算并和其他模型的计算结果进行了比较。     

三元混合制冷剂R32+R161+R1234yf气液相平衡实验研究

本文研究了含R1234yf的三元混合制冷剂的气液相平衡性质和模型,利用基于液相单相循环法搭建的气液相平衡实验装置,对温度范围为283.15～323.15 K的三元混合制冷工质R32+R161+R1234yf进行了实验研究,共得到45组实验数据。同时采用Peng-Robinson-Stryjek-Vera(PRSV)状态方程结合Wong-Sandler(WS)混合法则和Non-Random Two-Liquid(NRTL)活度系数模型,在前期工作得到的二元混合工质的模型参数的基础上,对三元混合工质气液相平衡性质进行推算。最后将模型推算结果与实验数据进行对比,结果表明系统压力平均绝对偏差AAD_p为0.34%,系统组分R32和R161的气相摩尔分数平均绝对偏差AAD_y_1和AAD_y_2分别为0.002和0.001。     

制冷剂/润滑油汽液相平衡实验系统的研制与验证

针对制冷剂/润滑油相平衡测量,本文研制了一套基于循环法的高精度制冷剂/润滑油气液相平衡实验系统。该实验系统在循环系统上安装了可拆卸的样品罐,将循环法与称重分析法结合,避免了等体积饱和法由于理想假设而产生的系统误差,可适用于温度范围为263.15~373.15K的制冷剂/润滑油气液相平衡的测量。测量了温度为293.35?323.33K的R290的饱和蒸气压,与NIST数据库相比,最大相对误差为-0.18%。同时,测量了温度为303.35K的R290和角鲨烷的相平衡,并使用Aspen Plus中的PR方程结合单流体的van der Waals混合规则对实验结果及文献值进行了关联,本文和文献的最大相对误差分别为-0.37%和-0.76%。     

R1234yf/R290/R134a系气液相平衡的模拟

本文从理论方面研究了混合制冷剂的相平衡特性,基于Peng-Robinson(PR)状态方程与Wong-Sandler(WS)混合法则,结合Predictive Soave Redlich Kwong(PSRK)方程中使用的UNIFAC基团贡献法,构建了混合物气液相平衡预测模型(PRWS-UNIFAC-PSRK)。结果表明:二元混合物R32/R1234yf的压力及气相质量分数的模拟结果与实验值偏差分别在±2.5%和±0.02内;三元混合物R134a/R1234yf/R600a的压力及气相组分质量分数计算值与实验数据的偏差基本在±3%和±0.04内;建立了R1234yf/R290/R134a系的三元相平衡图,当质量分数在0.25/0.70/0.05左右时存在共沸点。通过采用多参数状态方程,改进活度系数模型,获取更为准确的二元相互作用系数,可进一步提高模型的预测精度。     

四种制冷剂重力再循环蒸发器的理论计算与实验研究

本文建立了均相流模型,对四种制冷剂重力再循环蒸发器进行理论分析,并搭建重力再循环制冷系统实验台,在不同工况下对比了实验结果与理论计算结果。以R404A为例,当保温体内空气温度从0℃下降到-25℃时,传热系数的理论值与实验值的偏差从15.91%逐渐减小到3.01%,制冷量的理论值与实验值的偏差从14.43%逐渐减小到2.07%。保温体内空气温度越低,偏差的幅度越小,重力再循环制冷系统的运行状态和理论运行状态较吻合。应用该模型对四种制冷剂运行状态进行预测,预测结果表明:相比于其他三种制冷剂,当液柱高度较低时,R410A的传热系数和制冷量最大。     

冷水机组采用R22／R114的理论和试验研究

在 LS—500型冷水机组中用 R22 R114取代 R22作为制冷剂进行试验,在相同的最低蒸发温度和最高冷凝温度试验条件下,结果表明 R22/R114较 R22有明显节能效果,COP 提高30～40(?),量冷量有不同程度下降。以 MH—81方程为基础,采用常数混合法则计算R22 R111的汽液相平衡和热力性质。对冷水机组进行的模拟计算与试验结果较为吻合。     

非共沸混合制冷剂气液相平衡参数的计算

本文研究了改进的RKS方程在非共沸混合制冷剂气液相平衡参数计算中的应用，计算了非共沸混合物R14／R23的气液相平衡数据，结果表明：改进的RKS方程用于计算非共沸混合物的气液相平衡具有较好的准确性。     

添加剂对静态条件下HCFC-141b水合物生成的促进作用

本文针对静态条件下水合物形成诱导时间长、生长缓慢、随机性大的问题,实验研究了静态系统中HCFC-141b(R141b)制冷剂水合物的生成促进技术以及表面活性剂SDS、Cu丝对HCFC-141b水合物形成的促进作用。研究结果表明SDS和Cu丝可大幅缩短HCFC-141b水合物形成诱导时间,促进静态条件下水合物的快速生成。实验发现SDS+Cu丝促进体系中的SDS添加量存在最佳质量浓度,SDS的最佳质量浓度为0.1%,在此条件下水合物形成平均诱导时间约为1.3 h,水合物生成重复性好,生成的水合物密实。     

基于COSMO-RS的单工质气液相平衡热物性计算方法

本文对基于真实溶剂似导体模型(COSMO-RS)的单工质制冷剂气液相平衡热物性的模拟精度进行了研究。研究结果表明,调节分子的表面面积比例因子可以改善模型精度。将制冷剂单工质分为无机物、碳氢化合物(HCs)和氢氟烃类化合物(HFCs)3类,在最佳比例因子参数下,模拟值与NIST实验值的相对误差,无机物CO_2和NH_3分别在±3%和±1%以内,HCs和HFCs在±2%以内。在此基础上,分析各类工质的尺寸因子参数的变化规律,并拟合出各类单工质的饱和蒸气压方程,为新型单工质的气液相平衡热物性预测提供了新方法。     

浅谈凝析气藏水合物生成预测和防治措施

本文根据凝析气藏水合物的特点,介绍了水合物生成预测的主要方法相平衡常数法;根据水合物的生成条件,阐述了防止水合物形成和排除已生成水合物的常用技术,包括除水法、加热法、降压法、加化学添加剂法等。目前吉林油田凝析气藏水合物的防治技术主要采取加热力学抑制剂法。     

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.     

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 ...