异型材挤出模头压力降的数值计算

介绍了一种基于横截面法的异型材挤出成型中熔体在模头内流动压力降的数值计算方法，可用于预测截面复杂的异型材挤出模头的压力降：并通过算例说明了数值计算结果的可靠性和用途。     

塑料异型材挤出口模设计的数值模拟概述

从挤出口模设计原则出发,综述了数值模拟技术在塑料异型材口模流道的曲面构型,入口角和压缩比、降低或消除挤出胀大和挤出口模成型段的设计、熔体流动平衡和压力降的研究进展,以及口模设计的发展趋势.     

塑料异型材挤塑模模头校核

通过对塑料异型材挤出模模头结构进行分析,以聚合物流变学为理论基础,对机头流道的不同区域分别建立压力降计算公式和熔体停留时间计算公式,同时,通过对分流支架及型芯连接螺相进行受力分析,从而建立强度校核公式,最后介绍了以PBA为工具对AutoCAD进行二次开发,并编制了塑料异型材挤出模的分析验算程序。     

不等壁厚塑料异型材挤出模头稳定性的研究

针对塑料门窗发展中对不等壁厚异型材的需要,通过对不同结构的不等壁厚流道中熔体流动过程的数值模拟,展现出流道结构设计对模头挤出稳定性的影响,指出了合理的阻流块设计是对模头挤出稳定性更有利的出口平均流速调节方法,为不等壁厚异型材挤出模头的合理设计提供了依据。     

壁面滑移对塑料异型材共挤影响的数值模拟研究

在壁面滑移的边界条件下,利用流体有限元分析软件Polyflow,采用Giesekus本构方程,对L型塑料异型材进行了三维等温共挤出数值模拟。分析了滑移系数对共挤出胀大和粘性包围、口模出口面的剪切速率场及共挤出口模压力降的影响。研究表明,随着滑移系数的增大,共挤出胀大和粘性包围、口模出口面的最大剪切速率及口模压力降也逐渐增大,且滑移系数介于105和108之间时增速最大;滑移系数越小,共挤出制品质量越好。     

塑料挤出模头设计简析

挤出模是异型材挤出生产中的关键设备之一。挤出模主要由挤出模头和定型模组成，异型材挤出模头的主要功能就是将挤出机挤出的熔融塑料流束改变成截面近似于所需异型材截面的料坯。因此，在成型机组中，挤出机的挤出模头是非常重要的，它决定了型材的形状和型材制品质量的好坏，是挤出模设计中重点考虑问题之一。     

塑料异型材挤出成型的流动平衡分析

介绍了一种基于横截面法和流动路径法混合的异型材挤出成型中熔体流动平衡的分析方法，可用于确定具有多个分支流道、截面复杂的异型材挤出模头出口处物料的平均流速，帮助设计者判断模头流道设计是否合理，且计算量较小，适于工程应用。     

塑料异型材挤出模头稳定性设计的数值方法

根据挤出模头设计的最小横向流动理论，运用ANSYS有限元分析软件，模拟分析了两副模头分流段流道的三维非牛顿流场，讨论了分流段流道设计对模头稳定挤出的影响；指出分流段流道设计满足流动平衡条件时，流道横向流动最小，模头的稳定性能较好；并通过两副实际使用的挤出模具，验证了理论分析与实际的一致性，从而给出了塑料异型材挤出模头稳定性设计的数值方法。     

塑料异型材挤出膜中的压力分布

本文对塑料异型材挤出模机头典型流道结构进行了分析，给出了各种类型流道的压力降计算公式，并用一实例说明了文中所述方法的正确性。     

塑料异型材挤出模中的压力分布

本文对塑料异型材挤出模机头典型流道结构进行了分析，给出了各种类型流道的压力降计算公式，并用一实例说明文中所述方法的正确性。     

萃取精馏分离丁烷/丁烯

介绍了两种分离丁烷 /丁烯的方法 ,即乙腈 (ACN)法和二甲基甲酰胺 (DMF)法。对两种工艺流程进行了计算对比 ,DMF法工艺流程比ACN法简单 ,只需 3个塔。计算结果表明 ,DMF法再沸器和冷凝器能耗分别比ACN法降低 33.7%和 2 2 .7% ,选择DMF法萃取精馏分离丁烷 /丁烯效果较好。     

重量法和红外法测定外排水石油类物质的比较

针对锦州市环保监测站分析锦州石化公司外排水中石油类物质采用重量法,而公司环保监测站采用红外光度法引起的数据差异争端,对两种分析方法进行了对比.结论为重量法灵敏度低不适合分析含油低的外排水样,而红外法灵敏度高,分析含油低的外排水方法可靠、数据合理.建议外排水样采用红外光度法.     

Comparison of Eulerian-Lagrangian and Eulerian-Eulerian method for dilute gas-solid flow with side inlet

A Eulerian-Lagrangian method is implemented to simulate turbulent two-phase gas-solid riser flow, using a mean-field/probability density function (PDF) method. The mean-field method is applied to the gas phase while the PDF method is applied to the solid phase. Using the PDF method for the solid phase is advantageous as there is no need for closure models for the convection term in the momentum equation contrary to the situation where the mean-field method is used. The present method is implemented to investigate the influence of a side inlet on the flow pattern in a dilute gas-solid riser configuration. When applying the Eulerian-Lagrangian method, a perfect correspondence with the experimental observations is obtained. On the contrary, when using the Eulerian-Eulerian method significant differences with the experimental data are observed.     

新型曲线拟合法及在翅片管传热性能试验中的应用

引　言对于换热器的传热性能试验 ,往往需要得出换热面某一侧的对流换热系数及其换热规律 ,这就相应地需要根据换热器类型采用合适的试验方法 .一些学者针对具体的试件采用了各种形式的对流换热系数试验方法[1～ 3] ,但都存在各自的应用局限性 .曲线拟合法也是经常用到的一种方法[4 ,5] ,但常规的曲线拟合法或者存在较多的限定条件 ,或者拟合结果不太准确 .本文介绍的新型曲线拟合法限定条件少 ,拟合结果准确 ,试验方便 ,是一种行之有效的对流换热系数的试验方法 .1　新型曲线拟合法的原理1.1　一种简单的换热情形两种流体通过平壁进行热量…     

氟硅酸钾容量法测定磷矿石中的活性二氧化硅

介绍用硫磷混合酸分解样品,采用氟硅酸钾容量法测定磷矿石的活性二氧化硅,方法简单快速。结果表明,该方法的SD<0.03;CV<3.0,加标回收率在96.4%~104.8%,适合磷矿石中活性二氧化硅的测定。     

A new spectrophotometric method for the determination of ferrous iron in the presence of ferric iron

A new spectrophotometric method for the determination of ferrous iron concentration in samples containing ferric iron is presented. This new method is a modification of the Muir o-phenanthroline ferrous iron determination method. The new method consists of the quantitative spectrophotometric determination of Fe(II) by o-phenanthroline, but in which the ferric iron is complexed with sodium fluoride to eliminate interferences. A critical experimental comparison between the Muir spectrophotometric method, the Kolthoff titrametric method and the new proposed method is presented. Whenever Fe(III) accounts for more than 50% of the total iron in a sample, the method of Muir overestimates Fe(II). The proposed method has a range of 1–10 μg ferrous iron. It is as insensitive to other metal ions as the original method of Muir and is insensitive to Fe(III) up to a point where Fe(III) might be as high as 95% total iron. The proposed method is suitable for Fe(II) determination in bacterial leaching systems, where Fe(II) might be as low as 1% of total iron.     

An improved phosphorus assay for oils without carcinogenic hydrazine sulfate

An improved spectrophotometric method for phosphorus determination in oils is proposed. The proposed new method has made significant improvements in safety, sensitivity, and efficiency in comparison with the current American Oil Chemists’ Society (AOCS) Official Method (Ca 12–55, corrected 1992). The AOCS method employs hydrazine sulfate as the reducing agent to generate molybdenum blue. Hydrazine sulfate is a known carcinogen in laboratory animals and a suspected human carcinogen. The chemical also irritates skin and mucous membranes. In the improved method ascorbic acid is used as the reducing agent. Ascorbic acid is equally effective as hydrazine sulfate for the color reaction. The improved method is approximately 75 times more sensitive than the AOCS method. The sensitivity is improved by measuring absorbance at the absorption peak, 825 nm, and reducing the final volume of reaction mixture for color reaction. The AOCS method determines phosphorus by measuring absorbance at 650 nm, which is about 40% of that at the absorption peak. The efficiency of this improved method is also significantly increased by reducing sample size and the volumes of sample preparation. Therefore, the improved method is more cost-effective than the AOCS method because less chemical reagents and smaller glassware are used, and the hazardous chemical waste disposal cost is eliminated. The improved method also avoids concentrated HCl and 50% KOH for sample preparation.     

Quantitative determination of traces of free gossypol in fats,oils, and fatty acids by paper chromatography

Summary A quantitative method for the determination of traces of free gossypol in oils and fatty acids was developed. The method is based on the concentration of gossypol by extraction and quantitative paper chromatography of the extract. The method is specific for free gossypol and is not subject to interferences. The new method is both accurate and reproducible. The lower limit of detection is 10 p.p.m. The method is intended primarily for p.p.m. levels but is suitable for all concentrations. With slight modifications the method is applicable to meals. Presented at the fall meeting of the American Oil Chemists’ Society, Cincinnati, O., September 30 to October 2, 1957.     

对乙酰氨基酚的合成

本文总结了国内外近年来合成对乙酰氨基酚生产工艺的研究进展,主要介绍了传统二步法、新型二步法、一步法、逐步还原法和生化法,分析了各工艺的优缺点,提出了从环保上和经济上来考虑,新型二步法是对乙酰氨基酚合成的最好方法。     

复杂逆流多效蒸发系统常规设计的模型与算法

建立了有冷凝水闪蒸和额外蒸汽引出的复杂逆流多效蒸发系统的数学模型 ,常规逆流多效蒸发模型只是该模型的一个特例。提出一种新算法———迭代法结合矩阵法求解模型并给出算法框图。迭代法结合矩阵法与目前较先进的Broyden法相比 ,具有对初值要求不高、收敛稳定性好、收敛速度快等优点 ,是求解多效蒸发问题的一种新的有效方法。算例表明 :模型可用于复杂逆流多效蒸发系统的快速求解 ;对三效逆流蒸发NaOH溶液系统 ,采用冷凝水闪蒸可节省加热生蒸汽 10 %左右 ,节能效果显著 ;逆流多效蒸发采用生蒸汽或引出额外蒸汽预热原料液不仅不会节能 ,反而造成热能损失