Modeling of Caked Contacts in DEMs

When modeling the caking properties of bulk solids, it is not only necessary to incorporate the yield properties of individual particle contacts, but also to extend them to a many‐particle system. To accomplish this by means of Distinct Element Method (DEM) simulations a contact model for (spherical) particles, including a yield criterion for combined load is proposed. An application to the simulation of a caking test is presented and compared to experiments.     

Model for Gas‐Liquid Flow through Wet Porous Medium

A method involving bubbling of air through a fibrous filter immersed in water has recently been investigated (Agranovski et al. [1]). Experimental results showed that the removal efficiency for ultra‐fine aerosols by such filters was greatly increased compared to dry filters. Nuclear Magnetic Resonance (NMR) imaging was used to examine the wet filter and to determine the nature of the gas flow inside the filter (Agranovski et al. [2]). It was found that tortuous preferential pathways (or flow tubes) develop within the filter through which the air flows and the distribution of air and water inside the porous medium has been investigated. The aim of this paper is to investigate the geometry of the pathways and to make estimates of the flow velocities and particle removal efficiency in such pathways. A mathematical model of the flow of air along the preferred pathways has been developed and verified experimentally. Even for the highest realistic gas velocity the flow field was essentially laminar (Re ≈ 250). We solved Laplace's equation for stream function to map trajectories of particles and gas molecules to investigate the possibility of their removal from the carrier.     

不同流场状态对球形氢氧化镍生长粒度的影响

在相同的搅拌桨线速度、晶化时间、化学条件下,采用化学沉淀法分别应用八斜叶涡轮圆盘桨、推进式螺旋桨、Intermig桨分别制备球形氢氧化镍晶体。采用SEM技术考察各个样品的微观形貌,并结合PIV物理模拟技术分析不同桨型状态下反应器内的流场特性,研究表明:采用八斜叶涡轮圆盘桨是样品的球形度最佳,采用Intermig桨时样品的粒度d0.5最大。讨论了不同桨型对球形氢氧化镍晶体松装密度的影响。     

Validation of Gas Flow Measurement During Ozone Generator Performance Testing

Key measurements for ozone generator efficiency testing include generator power, ozone concentration, and gas flow rate. Accurate gas flow measurement must address numerous issues such as: meter precision, meter calibration, gas density changes due to variations in molecular composition, and gas compression and expansion changes due to variation in temperature and pressure. Preferably, the gas flowmeter for performance testing is one that can be field-verified for accuracy. Orifice-plate, flow-tube and venturi differential pressure flowmeters have these characteristics and have been frequently used to obtain gas flow readings of record during ozone generator performance tests. This paper discusses the importance of field-verification, provides reference equations and example calculations, and presents issues and considerations for quality assurance.     

气力流槽的设计计算

气力流槽是一种常用的固体粉料、粒料的输送设备。它适用范围广,结构简单,制造价格低廉。本文从理论上论述了影响气力输送物料流量的各个因素,为设计和使用设备提供了理论依据。     

两级石油化工流程泵的结构设计及应用

对离心式石油化工流程泵的不同结构进行了比较 ,指出了流程泵第 1级采用双吸叶轮、压水室为双涡室结构对于提高汽蚀性能和平衡径向力的重要作用。理论分析、试验结果及工业应用表明 ,采用小叶片出口角 β2 、少叶片数Z和大叶片包角θ的叶轮以及X形分布的两个中间过渡流道 ,能减轻泵的振动 ,提高效率 ,扩大高效区范围     

空气输送流槽的设计计算

空气输送流槽是一种利用压缩空气作为动力来输送物料的装置。本文介绍了空气输送流槽的输送原理和结构,并以炭黑输送为例,提出了设计计算空气输送流槽的简易方法。     

脉动流参数对旋流器分离性能的影响

介绍了脉动实验系统及相关的实验参数,研究了脉动流的一些主要参数对水力旋流器分离性能的影响,详细分析了脉动周期比、流量脉动幅值比和雷诺数等参数对水力旋流器用于细颗粒分离性能的影响。结果表明,在脉动周期比为0.68及流量脉动幅值比为2%左右等条件下,流量的脉动反而会提高水力旋流器的分离效率。     

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℃.     

离心流动包衣造粒装置

从流场分析与造粒机理出发 ,剖析离心流动包衣造粒机的组成、设计原则和制造与操作的技术要点。     

以铝矾土为原料制备氧化铝瓷球的原料设计和性能研究

针对目前精细氧化铝陶瓷存在的性能和价格矛盾,利用中国丰富的天然铝矾土矿物为主要原料,选用优化的工艺过程,添加少量的其他助剂,制备出了性能高的研磨介质.所制得的产品具有颜色白、性能高、烧成温度低、耗能少、资源消耗少、生产成本低等特点,减少了环境污染,实现了铝矾土的高附加值应用和高性能陶瓷的低成本制造,具有广阔的应用前景.     

多媒体制作的素材与流程分析

Macromedia Authorware是基于流程的多媒体创作软件,各功能模块可以独立制作,组合而成,本文着重分析了素材准备、流程录入、程序调试过程中常见的问题与对策,对多媒体制作具有良好的指导意义。     

Formation and Growth of Crystal Bridges in Bulk Solids

Solidification and caking of bulk solids often occurs during storage or while being transported to the customer. To investigate the formation and growth of solid bridges between two discrete particles, the modification of the contact region between these two particles stored in a climatic chamber is examined. The effect of load, temperature, relative humidity, and storage time on the formation of a bridge is analyzed. The objective is to describe the behavior of crystalline or salt‐like granules under real storage conditions.     

衣架式挤出模的流动模型分析及其简化设计的容许条件

从理论上分析了衣架式挤出模的两个流动模型,即熔体在扇形区内等压线平行于模唇(PIPDO)模型和任一流动路径上熔体的压力损失均相等(PLFPE)模型,并证明了这两个流动模型的等效关系。考虑到"蛤壳现象"对挤出模流动均匀性的影响,提出了挤出模简化设计的容许条件。