Influence of Bubble Bouncing on Mass Transfer and Chemical Reaction

The hydrodynamics of bubbly flows is dominated by bubble‐induced turbulence and bubble‐bubble interactions. Both phenomena influence the gas‐liquid mass transfer as well as the mixing of reactants. If the time scales of mass transfer and mixing are in the same order as the time scales of a parallel‐consecutive reaction, the yield and selectivity will be affected by the local hydrodynamics. An experimental setup is presented that enables the investigation of mass transfer during well‐defined and adjustable bubble collisions. The influence of CO₂ bubble collisions on mass transfer is measured and modeled with a modified Sherwood number correlation. Further visualization of the concentration field in the vicinity of O₂ bubbles by means of laser‐induced fluorescence demonstrates the dependency of mass transfer from a chemical reaction and permits the development of a first model approach.     

Influence of Chemical Reaction on Heat and Mass Transfer in MHD Radiative Flow due to Non-Coaxial Rotations of Disk and Fluid at Infinity

Theoretical Foundations of Chemical Engineering - An exact solution of the problem regarding influence of chemical reaction and buoyant force on the heat and mass transfer in a radiative flow due...     

Influence of Dispersed Particulates on Mass Transport in Cross-Corrugated Structures

A study of the effect of particulate solids on mass transport behaviour in cross-corrugated membrane systems is reported. The electrochemical limiting current technique was employed to determine the mass transfer coefficients. The influence of cross-corrugated structures, to simulate membranes, and the effect of the orientation of flow to the angle of corrugation (0°, 45° and 90°) on the mass transfer coefficient is reported. The effect of particulate solids on mass transport was investigated using SiO₂, at concentrations of up to 0.2 wt %. The presence of SiO₂, at a concentration lower than 0.2%, gave higher values of mass transfer coefficient compared to those in the absence of the solid. The mass transport correlations showed that even at low values of Reynolds number there is evidence of turbulence.     

微波辐射对淀粉化学变性反应的影响

传统化学变性淀粉主要是在常规加热条件下通过化学反应进行合成,普遍存在着反应时间长、产率低、能耗高等问题,而微波辐射技术可使淀粉的化学变性反应进行得快速、高效、节能和环保。文章简要阐述了微波促进淀粉化学变性反应机理,分析了微波辐射技术对不同类型化学变性淀粉合成反应影响,指出微波作为绿色合成技术在化学变性淀粉合成中具有重要的应用前景。     

Mass Transport and Chemical Demixing of Y-Ba-Cu-O Compounds During Sintering in Temperature Gradients

A thin cylindrical powder compact (3-mm diameter by 20-mm) with a nominal composition of YBa₂Cu₃O_x was sintered in a static temperature gradient of 25°C/mm in air for 12 h. The temperature at the hot end of the sample was maintained at 940°±5°C. Considerable mass transport and chemical demixing occurred along the length of the sample. The results are consistent with the formation of a liquid phase at the hot end of the sample, transport of the liquid down the temperature gradient, and the formation of different eutectic compositions along the length of the sample. The implications for processing high-T_c superconductors in the system Y-Ba-Cu-O are discussed.     

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.     

溶胀对中空纤维膜萃取器中的流动和传质性能的影响

溶胀是中空纤维膜萃取工业化必须要解决的关键问题之一。本文通过拍摄电镜照片，观察了溶胀前后中空纤维膜表面形态，孔隙率，膜孔径，膜孔道弯曲状况等微观结构的变化。结果表明，溶胀会使中空纤维膜孔隙率减小，膜孔径变小，弯曲因子增大，通过测量发现，溶胀后膜长度增加，而膜的内外径，膜厚基本不变。本文还研究了溶胀时间对中空纤维膜器中的流动及传质效果的影响，通过测量聚丙烯和聚砜中空纤维膜器管程和壳程的停留时间分布曲线表明，对于装填密度较高的膜器，溶胀时间对壳程和管程中的流动状况的影响可以忽略。此外，本文以正辛醇－苯胺－水为实验体系，在中空纤维膜器中进行了循环逆流传质实验。实验证明，由于溶胀使纤维膜阻增加，膜器的传质性能随时间的增加而下降。     

刮膜式分子蒸馏中液体流动形态的研究

分子蒸馏是一种高效的液液分离技术,但由于缺乏对其流体力学性质的认识,使得该项技术还多停留在实验室阶段.本实验通过高速摄像法,以水和丙三醇溶液作为测试液体,在冷模常压下,对在不同操作工况下蒸发壁面上的液膜形态进行图像记录,来研究刮膜式分子蒸馏设备内的流体力学性质.实验发现在整个操作过程中壁面主要出现4种不同的液膜形态:点状分布、线状分布、部分成膜和整体成膜.根据实验数据作出的壁面液体流型图证实了液膜形态与过程的转速,进料速度及物料性质有关.除此之外利用量纲分析法对影响成膜的各因素进行分析,得到与成膜过程相关的三个无量纲数∏1、∏2和∏3.使用非线性最小二乘法对实验数据进行拟合,得到整体成膜状态下方程∏3=f(∏1,∏2)的具体形式,再利用丙三醇作为测试液体验证了方程∏3=f(∏1,∏2)的准确性.结果表明成膜临界速度u*cr作为判断壁面流型的标准是可行的,其大小与过程的雷诺数、韦伯数及设备的高径比有关.成膜临界速度u*cr经验关联式的提出为分子蒸馏设备的理论研究和工业应用提供了参考.     

绘制甲醛标准工作曲线涉及的化学反应及影响因素探讨

采用乙酰丙酮分光光度法正确测定水性涂料中游离甲醛含量的关键是绘制甲醛标准工作曲线,对甲醛标准曲线绘制过程中所涉及的化学反应及影响因素作了分析和探讨。     

Nonlinear Heat and Mass Transfer with Consideration of Deformation in a Chemical Reaction Wave

A new approach is developed to perform mathematical modeling of heat transfer with consideration of deformation of a physical system in a chemical reaction zone. This approach describes boundary conditions using fractional differential-integral calculus. A numerical analysis using the model proposed is undertaken to examine processes during nonlinear heat transfer accompanied by deformation of a physical system due to intense gas release in chemical reactions, particularly in processes of the production of materials by self-propagating high-temperature synthesis.     

基于神经网络的两相流流型识别方法研究

采集了水平管内气水两相流动的差压信号,利用概率密度函数(PDF)对差压信号特征进行了分析;定义了PDF的四个特征参数,即PDF波峰个数K1、波峰峰值K2、波峰位置K3、以及PDF的方差K4来反映流型的特征。运用四个参数构成的特征向量对径向基函数(RBF)神经网络进行训练并识别流型,结果表明,该方法具有识别速度快、准确率高的特点,从而为两相流的流型识别提供了一种有效的手段。     

气液两相鼓泡塔流区及其过渡的混沌分析

应用确定性混饨分析技术,以气液两相鼓泡塔内的压力波动时间序列为分析对象,系统研究了鼓泡塔系统的混饨特性．结果表明,鼓泡塔内气液两相流动系统为混饨动力学系统,混饨特征参数最大Ｌｙａｐｕｎｏｖ指数、Ｋｏｌｍｏｇｏｒｏｖ熵和关联维数Ｄ２等可以有效地表征鼓泡塔的流区及其过渡．混沌分析为定量判别鼓泡塔的流区及其过渡提供了新途径．操作条件对鼓泡塔内气液两相流动的混沌特性影响显著,表现为混沌特征参数值随表观气速增加而增加,随表观液速增加而减小,但是,混沌特性随空间位置的变化不显著．     

喷射泵式气、液反应器的流型及其转变规律

本文研究了喷射泵式气、液反应器的四种流型及其转变规律.基于动量原理及能量、质量守恒定律,导得了判定反应器正常工作流型的判别式.实验验证了这种判别式.     

氢键对物质性质与化学反应的广泛影响

氢键是一种特殊的化学键合形式,在很多物质体系中存在着广泛的影响.在无机化学、有机化学、分析化学、生物化学、高分子材料等领域中,氢键都显现了特殊的重要性.讨论了氢键对物质的物理性质、酸碱性、物质结构与化学反应等方面的影响.     

气液并流筛板流态的模拟

文章利用CFX软件对开孔率为17%、150×120 mm的矩形气液并流筛板的气液两相流态进行模拟,分析了气液两相并流筛板的传质传热机理及筛板压降产生的主要原因。通过模拟研究了气液两相并流时气相和液相流量变化分别对塔板压降产生的影响。     

伴有二级不可逆反应的非牛顿幂律流体薄膜流中化学吸收的研究

本文对伴有二级不可逆反应的非牛顿幂律流体降膜流中的吸收过程进行了研究,提出扩散反应方程和它的解,并得到实验验证.     

基于流体诱发振动的非接触式湿气流流型识别(英文)

A novel noninvasive approach, based on flow-induced vibration, to the online flow regime identification for wet gas flow in a horizontal pipeline is proposed. Research into the flow-induced vibration response for the wet gas flow was conducted under the conditions of pipe diameter 50 mm, pressure from 0.25 MPa to 0.35 MPa, Lockhart-Martinelli parameter from 0.02 to 0.6, and gas Froude Number from 0.5 to 2.7. The flow-induced vibration signals were measured by a transducer installed on outside wall of pipe, and then the normalized energy features from different frequency bands in the vibration signals were extracted through 4-scale wavelet package transform. A “binary tree” multi-class support vector machine(MCSVM) classifier, with the normalized feature vector as inputs, and Gaussian radial basis function as kernel function, was developed to identify the three typical flow regimes in-cluding stratified wavy flow, annular mist flow, and slug flow for wet gas flow. The results show that the method can identify effec-tively flow regimes and its identification accuracy is about 93.3%. Comparing with the other classifiers, the MCSVM classifier has higher accuracy, especially under the case of small samples. The noninvasive measurement approach has great application prospect in online flow regime identification.