Experimental study of a liquid film flowing over a perforation

Perforations are one of the recognized geometrical features that contribute to liquid redistribution in corrugated sheet packings. Our experimental study focuses on a simplified but relevant configuration: a thin liquid film flowing on either side of a vertical plate with a circular perforation. We focus on the curtain mode when the liquid fills the perforation. Confocal chromatic imaging reveals a capillary ridge upstream of the perforation, an inertial ridge downstream, and a varicose capillary wave standing on the liquid curtain. We show that the wavelength is selected such that the velocity of the wave both satisfies Taylor's dispersion relation and matches the curtain local speed. We examine the effect of perforation size, supply conditions, and liquid properties on the curtain transition. Lastly, we propose a simple model based on a momentum balance that describes the effect of these parameters on the Reynolds number at which curtain forms.     

流动液膜的数值模拟研究综述

液膜流动现象广泛存在于自然界中,作为一种高效传热传质技术,其在化工等领域有着广泛的应用。近几年来,国内外学者越来越热衷于运用数值模拟技术来研究液膜的流动特性及传热传质特性。本文归纳分析了数值模拟研究中液膜自由液面的追踪方法。总结了不同壁面结构、不同壁面倾角、液体物性、液相流量与气相流速4个方面对液膜的流动特性的影响规律,以及改变壁面倾角、入口雷诺数、入口添加扰动时表面波呈现的波动特性。此外,还论述了流动液膜的传热传质特性的研究现状。所得结论对流动液膜的数值模拟研究具有一定的参考价值,最后提出了用数值模拟方法研究液膜流动的缺陷与不足,展望了更加科学合理地研究流动液膜的方法。     

Interaction dynamics of a spherical particle with a suspended liquid film

Hydrodynamics of collision interactions between a particle and gas‐liquid interface such as droplet/film is of keen interest in many engineering applications. The collision interaction between a suspended liquid (water) film of thickness 3.41 ± 0.04 mm and an impacting hydrophilic particle (glass ballotini) of different diameters (1.1–3.0 mm) in low particle impact Weber number ( ) range (1.4–33) is reported. Two distinct outcomes were observed—particle retention in the film at lower Weber number and complete penetration of the film toward higher Weber number cases. A collision parameter was defined based on energy balance approach to demarcate these two interaction regimes which agreed reasonably well with the experimental outcomes. It was shown that the liquid ligament forming in the complete penetration cases breaks up purely by “dripping/end pinch‐off” mechanism and not due to capillary wave instability. An analytical model based on energy balance approach was proposed to determine the liquid mass entrainment associated with the ligament which compared well with the experimental measurements. A good correlation between the %film mass entrained and the particle Bond number ( ) was obtained which indicated a dependency of Bo^1.72. Computationally, a three‐dimensional CFD model was developed to simulate these interactions using different contact angle boundary conditions which in general showed reasonable agreement with experiment but also indicated deficiency of a constant contact angle value to depict the interaction physics in entirety. The computed force profiles from computational fluid dynamics (CFD) model suggest dominance of the pressure force over the viscous force almost by an order of magnitude in all the Weber number cases studied. © 2015 American Institute of Chemical Engineers AIChE J, 62: 295–314, 2016     

阳树脂合成柠檬酸钙的电化学自动分析系统

基于流动注射流通式Na/Ca微电极串联动态电化学自动检测系统,给出了一种阳树脂在线离子交换连续合成高纯度柠檬酸钙的新方法,并实现了对阳树脂柱的运行状态及流出液中柠檬酸钙含量的同时自动在线监测。通过对此系统的相关影响因素进行了考察和优选,得到的结果是:检测系统的总离子强度调节缓冲液由80 mmol·L^-1 tris、175 mmol·L^-1 H₃BO₃、1 mmol·L^-1 KCl和0.025 mmol·L^-1 CaCl₂的混合液(pH 8.0)构成,样品注入体积为150 μl,总流量为2.26 ml·min^-1,混合盘管长度为120 cm(I.D.0.5 mm);检测系统的测定范围分别为2.0～1000 mmol·L^-1 Na⁺,0.2～50 mmol·L^-1 Ca²⁺;相对标准偏差(RSD)小于 0.68%;其检测下限分别为1.12 mmol·L^-1 Na⁺,0.093 mmol·L^-1 Ca²⁺。     

单个固体颗粒促进薄液膜破裂的格子Boltzmann研究

采用等温格子Boltzmann方法两相流模型结合颗粒运动模型对单个颗粒与薄液膜之间的相互作用进行了研究。通过模拟直观展示了单个球形疏水颗粒导致液膜破裂的详细过程,模拟结果表明与薄液膜接触的球形疏水颗粒会导致液膜弯曲变形从而产生毛细力,毛细力会驱动液膜在颗粒表面移动从而导致液膜破裂。疏水颗粒的接触角对液膜破裂的时间有明显影响,模拟发现接触角为106.7°的疏水颗粒导致液膜破裂时间最短。此外,当液膜的厚度发生变化时,颗粒导致液膜破裂的时间也会不同。     

超声脉冲反射法和激光吸收光谱法同步测量流动液膜厚度

液膜流动现象在工业过程中广泛存在,对流动液膜厚度测量方法的测量研究至关重要。首先利用已知液膜厚度的标准具（100～1000 μm）对超声脉冲反射法和激光吸收光谱法精度进行验证;结果表明,超声脉冲反射法测量液膜厚度的平均测量误差为1.07%,激光吸收光谱法测量液膜厚度的平均测量误差为1.29%。同时结合两种方法对流动液膜进行研究,结果表明,当液膜在低速/中速/高速流动时,两种方法测量流动液膜的平均厚度吻合良好,平均厚度差值分别为16.59、16.26、13.36 μm,流动液膜厚度的标准方差的相对偏差分别为0.29%、7.71%、25.37%,且在三种不同速度下两种方法测得在1s的周期内液膜波动次数一致。     

液氨卧罐液体实时连续泄漏建模及分析

基于范德瓦耳斯方程和流体力学理论,考虑液氨卧罐泄漏时罐压和液面面积变化,建立了液氨卧罐液体实时连续泄漏模型.利用模型对某制冷企业液氨卧罐进行数学模拟,并将计算结果与PHAST模拟结果进行对比分析.结果 表明,液面高度h下降幅度先减缓后变大,液体泄漏质量流率Qm和泄漏孔处液体泄漏速率v的下降幅度及泄漏液体质量m的增加幅度...     

A particle analyser for measuring particle size distribution and shape,on-line or in the laboratory

Norsk Hydro has developed a Particle Analyser for on-line or laboratory use, which measures particle size, size distribution and the deviation from sphericity (called nonspherical).The principle for this system is that the particles fall in a monolayer curtain in front of a high resolution CCD camera. The computer unit in the analyser measures and calculates the particle size and a sphericity factor for each particle. The data are presented as four real time trend curves, shown simultaneously for the on-line version. These curves show % oversize and fines, d₅₀ and the percentage nonspherical particles. For the laboratory version the data are presented in table and cumulative form.The on-line particle analyser has been installed in two of Norsk Hydro's prilling plants in Norway. The analyser has in both plants improved the product quality during the two years of installation.     

A phenomenological model for non-Faradaic material loss in flowing electrolyte without solid particle

The non-Faradaic material loss is the difference between the material loss measured by the weight loss method and the one determined by Faraday's secondary law. Being observable in flowing corrosive electrolytes, it is promoted by increasing wall shear stress and anodic dissolution, is reduced by the increasing strength of electrode, and disappears in quiescent electrolytes or under cathodic protection. Therefore, the non-Faradaic material loss is likely a result of certain corrosion-aided mechanical damage mechanisms. A phenomenological model is proposed for the quantitative evaluation of the non-Faradaic material loss. The applicability of this model has been verified by the test data measured in both aqueous and non-aqueous electrolytes.     

On the particle terminal velocity in a gas-liquid medium with liquid as the continuous phase

A mechanistic model was developed to describe the terminal velocity of spherical particles in a gas-liquid medium with liquid as the continuous phase. The model was established based on the momentum balance of a single particle taking into consideration the drag and buoyancy forces due to the liquid phase and the bubble-wake and particle interaction. The bubble-wake and particle interaction coefficient was shown to be a function of the particle properties only. A comparison of the particle terminal velocity between the model prediction and experimental data obtained in this study was also made over a wide range of particle size and gas velocity.     

基于粒子滤波联合估计的气相聚乙烯质量指标在线估计

针对气相聚乙烯生产中各种复杂的工况造成在线估计精度下降的现象,基于乙烯聚合机理并利用特征建模方法建立了聚乙烯质量指标预测模型,结合扩展卡尔曼滤波,提出了粒子滤波联合估计方法,即将状态和修正系数组成增广状态向量,实现对质量指标预测模型的在线滤波修正,并分析了基于粒子滤波估计的收敛性。所提方法在中石化某气相聚乙烯装置的长周期运行结果证实了所提方法的可行性和有效性,为实施聚乙烯装置的先进控制奠定了基础。     

液体洗涤剂连续配料工艺开发

简要介绍了国内液体洗涤剂的生产技术现状,阐述了间歇法生产工艺存在的不足及研发连续化生产工艺的必要性;针对间歇法生产工艺的生产瓶颈进行了分析,重点说明了在连续配料工艺生产中的改进措施;根据液体洗涤剂生产工艺及液体洗涤剂产品质量的影响因素,对生产工艺技术和投资两个方面的优势进行了比较分析,最后提出了连续配料工艺的技术优势、发展方向和应用前景。     

颗粒分析的样品制备

０引言在水泥工业中，用于检测的样品很多，如水泥、生料、煤粉及粉尘等，准确测试各样品的粒度分布，可为粉磨系统及相关设备提供工艺参数调整依据和检测生产控制过程中出现的问题。而在实际粒度分析中，经常出现许多错误的结果，经研究发现大部分都是因样品制备不合格而造成的，这是因为样品制备是保证正确测试的首要条件。样品制备是正式进行粒度测试前样品及测试条件的准备过程，包括样品的采集、缩分、分析样品用量的确定、分散介质、分散剂的选择、分散剂用量的确定及分散效果检查等。笔者曾在不同原理仪器上做过样品的制备试验（主要…     

Evidences for liquid encapsulation in PMMA ultra-thin film grown by liquid injection Photo-CVD

This paper deals with the characterization of ultra-thin films of PMMA grown by an original photo-assisted Chemical Vapor Deposition process equipped with a pulsed liquid injection system to deliver the monomer. The nanometric thick films showed a good ability to encapsulate a liquid phase as microdroplets protected by a thin polymeric tight membrane in the form of blisters. Techniques that are capable to analyze these heterogeneous structures at micro- and nanoscopic scale such as Raman Confocal Spectroscopy and Atomic Force Microscopy were used to characterize these polymer films. The liquid droplets were found to be monomer encapsulated by a PMMA film. The specific properties of these ultra-thin films exhibit self-healing capabilities at microscopic scale making them attractive for functionalization of surfaces and interfaces.     

Tailored surface roughnesses for enhanced deposition of fine liquid droplets from a flowing gas

Separating fine liquid droplets from a gas stream is an important operation in many industrial applications. In this paper, the effect of surface roughness on the deposition of droplets was investigated in a series of wind tunnel experiments. The roughness was modelled by 2-D rectangular ridges oriented at 45° to the flow direction. The rate of droplet deposition onto the surface was measured by a conductivity method. It was found that the deposition of droplets onto the roughened surface was enhanced by the roughness and the enhancement increased with ridge size-based Reynolds number. The maximum enhancement of droplet deposition on roughened surfaces over that of the smooth surfaces was observed to be around 150%. Data obtained for droplets with different sizes also indicated that the deposition rate of fine droplets was more dependent on the Reynolds than that of the large droplets. For relatively larger droplets, the enhancement of deposition is mainly caused by momentum-dominated impact. However, for fine droplets this is mainly due to the enhancement of local turbulence.     

A model-based scheme for the on-line optimization of a liquid extraction process

The on-line optimization of a liquid extraction process using a model-based scheme is described. Four steady-state process models are first investigated for their ability to predict the process performance; these models are subsequently used in the optimization study. The optimization scheme incorporates a simple model-updating technique and is based on an efficient method for constrained optimization which has been developed as part of this study. Rapid convergence to the true process optimum occurs, provided the predictions of the direction of change of the objective function are locally correct. In a few cases, however, poor model predictions result in failure to converge, or give convergence to a point other than the true optimum.     

连续通过式清洗机防范窜液的改进设刮

针对连续通过式清洗机存在的窜液问题,通过采取诸如风刀吹干系统设计、挡水板设计等技术改进方案,有效地防范了窜液问题的发生,并应用于生产实际,且收到了良好的效果。     

颗粒堆积型多孔介质内部液体形态实验研究及机理分析

实验研究了不同含湿率时堆积颗粒聚集状态和试样表观体积的变化,并分析了内在影响机理。含湿率较低时液体在试样内部的主要存在形式为液桥,含湿率较高时液体主要以联通液的形式存在,两种形态水分发生转换的临界含湿率由水在颗粒表面的表观接触角决定。试样内部液体形态及分布的演化,导致液体对颗粒的作用力发生变化,进而影响颗粒的聚集状态以及试样的宏观表观体积变化。利用建立的模型推导了液体形态发生转换的临界含湿率与表观接触角之间的函数关系,计算结果与实验具有较好的一致性。     

Thermodynamic analysis of liquid source chemical vapor deposition process for the preparation of a Ba-Sr-Ti oxide film

The equilibrium concentrations of the chemical species in a Ba-Sr-Ti-C-H-O system, corresponding to a liquid source chemical vapor deposition (LSCVD) process used in the preparation of barium strontium titanium oxide (BST) films, were determined by thermodynamic calculations. Ba(dipivaloylmethanato)2, Sr(dipivaloylmethanato)2, and Ti(tetra-isopropoxide) were assumed as the metal sources, and tetrahydrofuran (THF) and O₂ as the solvent and oxidant, respectively. An increase in the amounts of THF, a major source of graphite production, significantly increases the equilibrium concentrations of metal oxides and carbonates in the system. On the other hand, an increase in the O₂ content decreases the graphite content and increases the amount of carbonates. Based on these results, the conditions for an LSCVD process that produces minimum amounts of carbon impurities in a BST film were identified as a function of the process temperature and the O₂/THF ratio. The results of the equilibrium calculations are in reasonable agreement with experimental data, which indicates that the results can be used as a basis for identifying LSCVD conditions needed to prepare BST films with defined compositions. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.