Kenics型静态混合器的结构优化与数值模拟

基于三维有限元数值模拟方法,对应用于高黏聚酯熔体直纺工业丝过程中熔体管道输送的Kenics型静态混合器进行结构优化;对静态混合器内示踪粒子的流动轨迹进行统计学处理,通过停留时间分布、分离尺度、面积伸展率以及时间平均效率表征流动特性与混合性能。结果表明:相比传统静态混合器,当静态混合器的元件旋转角度为120°时,静态混合器的分离尺度降低,分散混合能力增强,拉伸作用增强,混合特性提高;相同管径下元件长径比为0.75时,静态混合器的混合能力较长径比为1.00或1.25时都有明显的提高;随元件长径比增加,混合效果逐渐变差,流动方式趋近于理想平推流动。     

Visualizing the topography of coating surfaces

An optical system for imaging the topography of (coating) surfaces using a video monitor is described. The grey level of the image correlates with the slope of the surface. The principle of operation of the method is explained and some applications are indicated.     

静态过滤器在盐水精制中的应用

目前国内使用的盐水过滤器包括国产PE精密过滤器、戈尔(GORE)膜液体过滤器以及美国颇尔(PALL)公司推出的新型通用舒马赫FT型表面过滤器，它们的过滤过程及反洗过程均具有静态过滤器的特征。笔者对静态过滤器的特征及影响过滤器性能的主要参数进行了分析，并对过滤器的滤芯结构、过滤形式、运行特征进行了比较。认为戈尔过滤器具有膜薄、滤芯有柔性、易清洗及装置较简单等优点。     

Experimental analysis of static pressure in bins

A pressure transducer with a pressure-high sensitive semiconductor gauge was used to measure distribution of vertical pressure at the base and horizontal wall pressure in a bin packed with glass beads, which are typical cohesionless particles.Even when the glass beads were uniformly supplied to the bin, the vertical pressure at the base was distributed unevenly, with the maximum and minimum values. This seems to be attributable to the “arching” which results from its nonhomogeneous configuration. In addition, the results indicate that the larger the diameter of the bin, the more numerous the extreme values of vertical and horizontal pressure become.This implies that the distribution of particles is the principal mechanism affecting the distribution of pressure in a powder bed. Consequently, to analyze the mechanism of a powder bed, the transference of force among the particles should be evaluated considering the distribution of the particles and paying careful attention to each of the particles in the powder bed.     

静态混合器在环保领域的应用

简述静态混合器的概念和特点 ,指出静态混合器在环保领域的应用及应用原理 ,列举了若干应用实例 ,期望能促进在环保领域进一步推广应用静态混合器。     

Controlling static electricity in PVC packaging

The importance of establishing a more sophisticated approach for the control of static electricity in PVC packaging has been underscored by the microelectronics industry and its need for protecting products from electrostatic discharge. Four basic classifications; conductive, static dissipative, antistatic, and insulative, as well as a series of acceptable definitions are now available. Insulative PVC is made conductive by the inclusion of conductive carbon blacks. Antistatic PVC is prepared by the incorporation of an antistatic additive in the compound or by topical application of an antistat from solution. There are no static dissipative additives as such. A more sophisticated approach, such as lamination of different materials is required to prepare a static dissipative product.     

Liquid dispersion in static in-line mixers

Liquid/liquid dispersion in static mixers has been investigated using Lightnin “In-liner” mixing elements. The average drop size was found to decrease with increasing residence time, gradually approaching an equilibrium size whose magnitude agrees reasonably well with Kolmogoroff's theory for drop rupture in turbulent flows. The efficiency at which mechanical energy is utilized in the generation of new interfacial area was evaluated as a function of design and operating conditions and was found to be highest when the final drop size is much larger than the achievable equilibrium value.     

X-ray topography studies of dislocations in single crystal CVD diamond

X-ray topography has been used to study single crystal diamond samples homoepitaxially grown by microwave plasma-assisted chemical vapour deposition (CVD) on high pressure high temperature (HPHT) and CVD synthetic diamond substrates. Clusters of dislocations in the CVD diamond layers emanated from points at or near the interface with the substrate. The Burgers vectors of observed dislocations have been determined from sets of {111} projection topographs. Dislocations have line directions close to the [001] growth direction and are either edge or 45° mixed dislocations. Where groups of dislocations originated at isolated points they tended to be of the edge variety. Where the substrate surface was deliberately damaged before growth, two sets of dislocations were observed to have propagated from each line of damage and there was a tendency for dislocations to be of the 45° mixed variety with a component of their Burgers vector parallel to the polishing direction. It is demonstrated that X-ray topography can be used to deduce the growth history of CVD synthetic diamond samples produced in multiple growth stages.     

Measurement of temperature fields in mixing vessels using optical topography

Experimental investigation of stirring processes require the measurement of temperature changes and concentration profiles in all the zones of the mixing volume. The conversion of simultaneous chemical reactions during the mixing process depends on the local temperature and concentration. The time-dependent temperature and concentration fields can be recorded for the entire mixing volume with the use of optical tomography and correlated with time. This technique offers the possibility of continuous measurement of temperature and concentration changes during the mixing process throughout the measurement volume. In the described investigations, optical tomography is used to examine the transport and equalization processes during mixing in stirred vessels.     

静态混合器在氯冷凝器中的应用

介绍浙江巨化股份有限公司电化厂采用在氯冷凝器中安装静态混合器的方法来提高液氯液化量的工艺改进方案,并对该工艺进行了理论计算与实际效果的对比,分析了理论与实际存在偏差的原因。     

Sensitivity analysis in static optimization of fermentation plants

Biotechnological processes are often characterized by uncertain model parameters, input variables which are difficult to handle and ill defined cost functions. Nevertheless, it is desirable to define optimal operating points. Starting with a robust approach for numerical optimization, the paper presents three different methods for evaluating the sensitivity of an optimal operating point to uncertain parameters or disturbances of the input variables. It is shown that sensitivity analysis can provide useful guidelines for designing biotechnical plants with invariant optimum operation in the presence of changing inputs or parameters.     

Evolution of surface topography in one-dimensional laser machining of structural alumina

High energy lasers are an emerging industrial tool to fabricate complex shapes on hard and brittle structural ceramics such as alumina. The selection of laser processing parameters and the prediction of material removal rates during the laser machining are the critical issues. This paper was attempted to present the state of the art of laser machining of alumina using an integrated experimental and computational approach. A multistep computational model based on COMSOL? Multiphysics was developed to study the influence of various single-pulse laser energy densities and associated physical phenomena (recoil pressure, Marangoni convection, and surface tension) on the temperature history, fluid velocity, crater size, and surface topography. A pulsed Nd:YAG laser was employed to machine alumina under different processing conditions. The surface topography of laser machined alumina was measured by an optical profilometer and the results were compared with the computationally predicted topographic parameters with reasonably close agreement.     

Surface topography and mechanical properties of carbon fibres

Surface topography of polyacrylonitrile based carbon fibres preoxidized under a variety of conditions has been studied in detail. Only those carbon fibres processed under optimum conditions are found to possess defect free surface topography. Changes in surface topography and the tensile strength of carbon fibres with processing conditions have been discussed.     

静态混合器在硝基苯生产中应用的侧流试验研究

介绍了静态混合器的混合原理,及其在硝基苯生产的中和、水洗工序的应用情况,与原来采用的釜式搅拌器进行了比较,结果表明,采用静态混合器进行酸性硝基苯的中和与水洗,酚盐的去除率能达到生产要求,软水的消耗量可降低50%。     

均四甲苯静态结晶动力学研究

均四甲苯与其同分异构体沸点相近、熔点相差较大,不适合采用精馏精制,而宜采用熔融结晶方法进行分离。在考虑固液相界面温度随冷剂温度变化的前提下,采用解析迭代法研究均四甲苯熔融结晶动力学并设计实验进行验证。利用非线性最小二乘法对等温实验数据进行拟合得到不同冷剂温度下的组合动力学参数,并通过多项式拟合得到了组合动力学参数随冷剂温度的变化关系。将其应用于模拟非等温结晶过程的晶体生长,计算结果与实验数据基本吻合,表明该模型能很好地预测晶层生长过程。     

Controlling flows in microchannels with patterned surface charge and topography

This Account reviews two procedures for controlling the flow of fluids in microchannels. The first procedure involves patterning the density of charge on the inner surfaces of a channel. These patterns generate recirculating electroosmotic flows in the presence of a steady electric field. The second procedure involves patterning topography on an inner surface of a channel. These patterns generate recirculation in the cross-section of steady, pressure-driven flows. This Account summarizes applications of these flow to mixing and to controlling dispersion (band broadening).     

V型静态选粉机的改造

辊压机挤压做功能力差、入磨物料粗等工艺问题系下料溜子结构不合理与V型选粉机出风口导风叶片偏多致V型静态选粉机分级效果差引起.在下料溜子增加“品”字型排列的V型折流板和封堵V型静态选粉机出风口部分导风叶片后,V型静态选粉机分级效果得到明显改善,辊压机运行更加稳定,挤压效果明显提高,水泥磨粉磨能力有较大幅度增加,系统产量提...     

我厂立式电收尘器的改造

０前言我厂有４条３．０m×８８．６５m湿法窑水泥生产线,窑尾均配有４０m２立式电除尘器。立式电除尘器大多应用于老式水泥回转窑的窑尾,因技术和管理等原因,除尘效率难以大幅度地提高,除尘器出口粉尘排放浓度长期不能达到国家环保要求。一些水泥厂已将立式电除尘器改造成为卧式电除尘器,但目前国内仍有数十台设备在使用。本文就我厂对立式除尘器实施成功改造的经验作一介绍。１立式电除尘器存在问题我厂立式电除尘器运行故障统计见表１,运用中存在的主要问题,则主要有下述方面。（１）电除尘器的原星形阴极线不易张紧（其采用的是…