Flow and Flow Decay of Refractory Castables

Installation of refractory castables depend not only on flow,but also on how soon the flow is lost because of setting.The loss of flow(flow decay)has always been one of the main problems of refractory castable manufacturers,a problem that has not been too well described in literature.The flow decay has been studied for a castable system based on alumina,pointing out some general trends.The flow decay was found very temperature sensitive,being strongly accelerated by temperature increases.To compensate for excessive flow loss,a retarder like citric acid may be used.Thus flow decay was measured as a function of citric acid(retarder) addition at 35℃.     

Flow Regime Identification of Gas-liquid Two-phase Flow Based on HHT

A new method to identify flow regime in two-phase flow was presented, based on signal processing of differential pressure using Hilbert Huang transform （HHT）. Signals obtained from a Venturi meter were decomposed into different intrinsic mode functions （IMFs） with HHT, then the energy fraction of each intrinsic mode and the mean value of residual function were calculated, from which the rules of flow regime identification were summarized. Experiments were carried out on two-phase flow in the horizontal tubes with 50mm and 40mm inner diameter, while water flowrate was in the range of 1.3m^3.h^-1 to 10.5m^3.h^-1, oil flowrate was from 4.2m^3.h^-1 to 7.0m^3.h^-1 and gas flowrate from 0 to 15m^3.h^-1. The results show that the proposed rules have high precision for single phase, bubbly, and slug, plug flow regirne identification, which are independent of not only properties of two-phase fluid. In addition, the method can meet the need of industrial application because of its simple calculation.     

Method to Characterize the Air Flow and Water Removal Characteristics during Vacuum Dewatering. Part I—Experimental Method

An experimental method using a novel design to characterize the air flow and water removal during vacuum dewatering in paper manufacturing is discussed. The experimental setup involves the intermittent application of vacuum, similar to commercial systems, using a rotating disk with slot opening arrangement. The system is capable of commercially realistic residence times of the order of milliseconds. The intermittent application of vacuum simulates vacuum dewatering on commercial paper machines. The air flow rate is calculated from changes in pressure and temperature in the vacuum tank underneath the sample. The role and importance of air flow during vacuum dewatering is studied by accurately measuring the air flow, properly taking into account the leaks during vacuum dewatering. The method described here provides for the first time accurate air flow and water removal data during vacuum dewatering. Methods of analysis of the experimental data are also presented. This information can be used to better understand the water removal process as well the role and importance of air flow during vacuum dewatering.     

浅析白垩储库Mass Flow的设计

库的Mass Flow设计是指库应按照物料性质选择合适的仓角、内衬材料、仓的形状、储存时间及出口开口尺寸,以保证物料在库内不结拱、不堵塞。用此法来指导白垩储库的设计,可提高库储运的可靠性,从而减少投产后的维护工作量。     

应用SolidWorks Flow Simulation优化定子结构

应用Solid Works Flow Simulation软件对1款乳化头的4个不同定子结构进行了CFD(计算流体力学)分析,通过仿真计算,直观获得了釜内不同乳化头周围的流体速度分布云图和流线轨迹;通过粒子示踪法模拟了制胶物料在乳化头作用下的分布状态;最后在定子外围设定草绘面,并获取该面上的平均速度,以定量预测和对比不用定子结构的乳化效果。研究结果表明:通过CFD分析,可从4个方案中选择最佳结构的定子,从而达到优化定子的目的;在4个定子结构中,无顶梢且上宽下窄型出料口的定子具有相对最好的分散效果。     

In Situ Investigation of Two-Phase Flow Patterns in Flow Fields of PEFC’s Using Neutron Radiography

A novel in situ method for the investigation of the two-phase flow patterns occurring in the flow fields of polymer electrolyte fuel cells (PEFC’s) has been developed. In these experiments, the gas / liquid two-phase flow in hydrogen fuel cells as well as in direct methanol fuel cells (DMFC’s) has been studied. Unique results and the promising use of neutron radiography for PEFC research are shown. Its current limitations but also future developments and opportunities are discussed.     

Modeling of a Reverse Flow Reactor for Methanol Synthesis Modeling of a Reverse Flow Reactor for Methanol Synthesis

An accurate one-dimensional, heterogeneous model taking account of axial dispersion and heat transfer to the reactor wall, and heat conduction through the reactor wall for methanol synthesis in a bench scale reactor under periodic reversal of flow direction is presented. Adjustable parameters in this model are the effectiveness factors for each of the three reactions occurring in the synthesis and a factor for the bed to wall heat transfer coefficient correlation. Experimental data were used to evaluate these parameters and reasonable values of these parameters were obtained. The model was found to closely predict the reactor performance under a wide range of operating conditions, such as carbon oxide concentrations, volumetric flow rate, and cyclic period.     

基于Mold Flow的电机机壳的优化设计

利用模流分析软件Mold Flow在计算机上对注塑成型过程进行模拟分析,在产品制造前期对产品制造过程中的变形进行预测并修正。通过计算机辅助设计,不仅缩短了产品的设计开发周期,而且保证了产品的制造精度,提高了电机的精度和使用寿命。     

基于SolidWorks Flow Simulation乳化头效果分析

应用SolidWorks软件的Flow Simulation插件对乳化头部件进行了计算流体力学(CFD)分析,模拟了4个CFD项目:(1)流体为水、转速3 000 r/min;(2)流体为一种高黏度流体、转速3 000r/min;(3)流体为水、转速6 000 r/min;(4)流体为一种高黏度流体、转速6 000 r/min。通过流体动力学仿真分析,获得了不同黏度的流体、不同转速下的流场运动分布速度云图及带矢量云图;通过粒子轨迹示踪法,直观地观察到物料粒子在乳化头作用下的分散效果。当流体黏度低时,提高转速可明显提高分散效果,而当流体黏度高时,提高转速对分散效果的改善并不明显。因此,CFD流体分析可为乳化头结构的优化设计提供有力的参考。     

Numerical Study of Solid-Liquid Two-Phase Flow in Stirred Tanks with Rushton Impeller (Ⅰ) Formulation and Simulation of Flow Field

Three-dimensional solid-liquid flow is mathematically formulated by means of the "two-fluid" approach and the two-phase k-ε-Ap turbulence model. The turbulent fluctuation correlations appearing in the Reynolds time averaged governing equations are fully incorporated. The solid-liquid flow field and solid concentration distribution in baffled stirred tanks with a standard Rushton impeller are numerically simulated using an improved "inner-outer" iterative procedure. The flow pattern is identified via the velocity vector plots and a recirculation loop with higher solid concentration is observed in the central vicinity beneath the impeller. Comparison of     

Three Dimensional Simulation of Liquid Flow on Distillation Tray

The liquid flow on a single-pass sieve distillation tray is simulated with a three-dimensional computational fluid dynamics (CFD) program with the K-ε turbulence model. In the model, a source term SMi is formulated in the Navier-Stokes equations to represent the interfacial momentum transfer and another term SC is added to the mass transfer equation as the source of interfacial mass transfer. The simulation provides the detailed information of the three-dimensional distribution of liquid velocity on the tray, the circulation area and the concentration profile along the height of liquid layer.     

Numerical Simulation on Gas-Solid Two-Phase Turbulent Flow in FCC Riser Reactors(Ⅱ) Numerical Simulation on the Gas-Solid Two-Phase Turbulent Flow

Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion model for FCC riser reactors given in Part Ⅰ of the present paper.Detailed information about the turbulentflow fields in the riser reactor obtained revealed the basic characteristics of the gas-solid two-phase turbulentflows when heat transfer and catalytic cracking reactions were co-existing in the riser.Results showed that thedistributions of the flow,the turbulence kinetic energy and the catalyst particle concentration are not uniform inthe axial,radial and tangential directions.The most complicated part of the riser reactor is the feed injectingzone.The complicated configuration of the turbulent gas-solid two-phase flows would exert a great influence onthe results of interphase heat transfer and cracking reactions.     

The Flow and Fracture of Advanced Glasses — an Overview

Editors' note: On appropriate occasions, the International Journal of Applied Glass Science will engage the services of Guest Editors to help focus on topics of special interest to the international glass community. In this inaugural issue of this initiative, Professors Tanguy Rouxel and Richard Brow have accomplished just that in their overview of the subject “Flow and Fracture of Advanced Glasses.” An introduction to this material and brief biographical sketches are given below. Our sincere thanks are extended to them for their help and cooperation throughout this undertaking, and especially the authors who contributed so much of their time, energy, and talents to making this special issue possible.     

Local Measurement of Gas-Liquid Bubbly Flow with a Double-Sensor Probe

A double-sensor probe was used to measure local interfacial parameters of a gas-liquid bubbly flow in a horizontal tube. The parameters included void fraction, interfacial concentration, bubble size distribution, bubble frequency and bubble interface velocity. The authors paid special attention to the probe design and construction for minimizing measurement errors. Measures were also taken in the design of sensor ends for preventing corrosions in the flow. This is an effort to improve the current double-sensor probe technique to meet the ever-increasing needs to local varameter measurements in gas-liquid two-phase flows.     

Computational Fluid-dynamics of Liquid Phase Flow on Distillation Column Trays

A computational fluid-dynamics model is presented for predicting the two-phase two-dimensional liquid phase flow on a distillation column tray based on the modification of Navier-Stokes Equation by considering both the resistance and the enhanced turbulence created by the uprising vapor. Experimental measurement of the local liquid phase velocity on an air-water simulator of 1.2m in diameter by using the hot film anemometer is briefly described. Two of the conventional fluid-dynamic constants are readjusted for the case of liquid flow on a tray by fitting the experimental data. The predicted local liquid phase velocity and direction of flow by the present model are confirmed satisfactorily by the authors' experimental measurements and by the data from literature. By the aid of the present model, the concentration field on the tray can be computed for the evaluation of the enhancement of liquid phase concentration across a tray. The advantages of applying computational fluid-dynamics to tray column design     

应用Flow 2000软件分析功能块成型结构的设计

利用Flow 2000软件，从3个方面对塑料异型材挤出模头中功能块成型结构的设计进行了分析，即进行部分功能块的结构改进、流道中功能块局部流速过慢的处理、流道中功能块局部流速过快的处理。从而确保成型区上功能块的流道截面图形设计及平直段长度的设计满足挤出模头流道设计的基本要求，提高了挤出模具的设计水平，缩小了与国外设计上的差距。     

A Hydrodynamic Modei for Slug Frequency in Horizontal Gas-Liquid Two-Phase Flow

The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrody-namic modei was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug frequency on the frequency of unstable interfacial wave. Using air and water, experimental verification of the modei was carried out in a large range of flow parameters. Six electrical probes were installed at different positions of a horizontal plexiglass pipe to detect slug frequency development. The pipe is 30m long and its inner diameter is 24 mm. It is observed experimentally that the interfacial wave frequency at the inlet is about l to 3 times the frequency of stable slug. The slug frequencies predicted by the modei fit well with Tronconi (1990) modei and the experimental data. The combination of the hydrodynamic modei and the experimental data results in a conclusion that the frequency of equilibrium liquid slug is approximately half the miniraum frequency of interfacial wave.     

基于Poly Flow模拟分析的新型流道系统设计与分析

塑料板膜挤出机头是挤出热塑性板片材的关键性部件。设计不良几何流道将会导致口模出口挤出速度不均及物料在机头内滞留而热分解,从而引起挤出板片材的横向厚度不均及产品质量下降等问题。本文基于PolyFlow数值模拟分析,以直锥管衣架式机头为基础,提出一种新的流线型流道系统设计方法。经优化设计参数,从模拟结果中取得了良好的挤出效果。并通过了初步的实验验证。