液体蒸汽向单气泡中传质过程的数值分析

<正>当气体通过液相介质时,由于气液界面和气相主体间存在液体蒸汽的浓度差,使液体迅速蒸发,可以大大强化对流传热及沸腾传热.此外,在鼓泡设备中,这种溶剂汽化现象亦可能对气含率及传质带来很大影响.因此,定量地分析液体蒸汽向气泡中传质的过程是很有意义的.此过程为具人体积变化的自由边界问题.对于核状沸腾过程的自由边界问题已有很多研究,其气泡长大的控制步骤为兴高采烈相可能提供的气化潜热速率,而由于气泡中质量传递控制的移动边界问题尚未见有研究.本文提出了液体溶剂向单气泡中传质的数学模型,获得了数值解.并且对各种影响因素进行了讨论.     

气泡在粘弹性液体中溶解的研究进展

在发泡塑料的制造过程中，均相气体－聚合物体系的形成直接影响了制品的物理机械性能，因此了解气泡在粘弹性液体中的溶解机理成为必然。本文讲述了气泡在流体中塌陷行为的研究进展。对Rayleigh对低粘度牛顿流体，Foqer和Goddand在无线量线性Maxwell模型的粘弹性体，Tanasawa和Tang用oldroyd三常数粘弹模型等科学家的研究行为做了概述，总结出影响此过程的复杂的影响因素，并指出进一步的研究方向。     

基于图像处理的气固流化床中气泡行为的分析

以数字图像处理为基础,实现对流化床中气泡的成长、聚合和分裂行为的分析.利用高速摄像机拍摄气固两相流的气泡运动图像,从中选取气泡上升、聚舍和分裂三种典型图像序列.经过图像处理后,分别对其进行气泡识别和参数的获取.然后根据获取的数据,首先分析了气泡上升过程中面积、形心、等效直径等参数的变化趋势和变化规律,接着对聚合中的聚合...     

液-固流化床中单个变形气泡的上升速度

以气泡在上升运动过程中的受力分析为基础,建立了描述单个变形气泡在液－固流化床中上升速度的理论模。应用该模型分别对球形和球帽形气泡在液－固流化床中的上升速度进行了计算,并将计算民在不同的床内压力,温度与颗粒相体积分数下气泡上升速度的实验测量数据进行了比较。     

微孔发泡的气泡成核理论研究现状

对经典成核理论进行了探讨,分析了其在描述流场中气泡成核时的局限性;详细讨论了国内外关于剪切流场中气泡成核的理论模型,并指出了气泡成核研究的未来发展方向。     

筛板上液体横向流动时气泡的形成特性

An apparatus,desinged to simulate bubbling of a sieve tray operated in froth regime,was employed. Bubble contact angles in and above the incipient weeping regimer for an air-water-plexiglas system were investigated. The influence of both liquid cross-flow and gas up-flow upon bubble contact angles was examined. A model considering the influence of liquid cross-flow was developed to predict bubble size from a sieve hole in froth operation regime.The comparison shows that the bubble sizes predicted by the present model are consistent with our experimental values and the available published experimental data.     

剪切流场中微孔发泡的气泡成核理论研究现状

分析了经典成核理论对于动态聚合物熔体中气泡成核的局限性；概括了剪切流场中气泡成核的研究进展，并对剪切流场中泡核拉伸模型、空穴成核模型进行了详细的分析和讨论，指出了其对气泡成核过程解释的不足；介绍了最新的气泡成核中的剪切能成核理论，该理论较完善地解释了剪切流场中气泡成核过程；最后指出了气泡成核研究的发展方向。     

气-液-固三相流化床中气泡大小分布的随机模型

本文利用马尔柯夫过程理论,建立了一个包括气泡上升速率、气泡大小以及气泡在床内出现位置的随机模型.利用热力学理论分析了模型参数.同时,本文利用四组元组合电导探针测定了气泡大小及其分布密度,验证了随机模型.结果表明,模型值与实验拟合很好.     

气泡驱动液固流化床内二元颗粒的流化行为

采用密度稍重于和稍轻于流体的两种颗粒,研究了气泡驱动液固流化床内二元颗粒的流化行为。通过测量压差和拍摄视频的方法确定了初始流化气速U_in,g、固含率和气含率。重颗粒的U_in,g通过流化床底部的压差变化确定,轻颗粒的U_in,g则通过观察得到。研究表明,在气泡驱动的液固流化床内,重颗粒和轻颗粒的初始流化气速都随藏量的增加而增加,但重颗粒增加幅度更大。完全流化后,重颗粒固含率在轴向上分布不均匀,而轻颗粒则分布较为均匀。在二元颗粒体系内,上部轻颗粒的流化受到下部重颗粒的影响而底部重颗粒的流化不受轻颗粒影响,导致重颗粒U_in,g和固含率分布主要受自身藏量影响,而轻颗粒U_in,g随二元颗粒的总藏量变化。     

固含率对沸腾床反应器气泡行为的影响

采用动态气体逸出法,在高7.0 m、直径0.3 m的有机玻璃塔中研究了固含率对沸腾床反应器内气泡行为特性的影响。在表观气速2.16~21.62 cm/s和固含率9.8%~39.0%（体积分数）范围内测定了反应器内的总气含率、大小气泡含率、大小气泡上升速度及其尺寸等参数。结果表明：总气含率随着表观气速的增大而增大,随着固含率的增大而减小。随着表观气速的增大,大气泡含率、大气泡直径及其上升速度均呈增大趋势;小气泡含率明显增大,但小气泡上升速度和直径趋于减小。随着固含率的增大,大气泡含率略有降低,但大气泡直径及其上升速度都明显增大;当固含率超过19.5%（体积分数）后,小气泡上升速度几乎下降为0;当固含率达到29.3%（体积分数）时,小气泡基本消失。     

Hydrogen and Oxygen Bubble Attachment to a Bitumen Drop

Air bubble – bitumen attachment is a critical step in the flotation of bitumen from mined oil sand. In this study, single bubble – bitumen drop attachment was observed directly using a novel experimental technique. Induction time is determined and used as an indication of bubble‐bitumen attachment potency for both hydrogen and oxygen bubbles. The attachment tests were conducted in deaerated municipal water (City of Edmonton tap water) at temperatures ranging from 22–50°C. Induction times measured for hydrogen bubble attachment were shorter than those for oxygen bubbles. Coalescence tests were also conducted in the absence of bitumen, and showed that hydrogen bubbles coalesced more rapidly than oxygen bubbles in both deaerated municipal water and clear (solids‐free) process water.     

Pulsation Model of the Detachment of a Vapor Bubble from a Solid Wall

A pulsation model is suggested for the detachment of a vapor bubble that is growing on a solid wall according to a prescribed law.     

Bubble Formation in Thin Polymer Films on Solid Substrates

Bubble formation takes place in thin polymer films on hydrophilic solid substrates when heated after annealing. The bubbles form only when the polymer has unsaturated carbon double bonds. Therefore, staining of such a polymer prevents the formation. The formation is also prevented by heating at atmospheric pressure rather than under vacuum. The size of the bubble decreases with increasing temperature and also with increasing time.     

液晶玻璃基板气泡缺陷分析与对策

基于液晶玻璃生产中气泡缺陷分析,就气泡缺陷的分类、产生原因及对策方法展开分析讨论,为液晶玻璃生产气泡缺陷分析对策提供思路,提高对策效率。     

多层鼓泡塔中液体轴向混合的研究

本文分两部分,在第Ⅰ部分中以实验验证了级内完全混合——级间有返混模型用于多层鼓泡塔的适用性。在空气-水系统中,用稳态示踪方法分别测定各级间的返混系数。从统计力学的观点,将本文及西胁昭雄在大孔径、大开孔率范围的实验结果进行了统一关联,得到一较普遍的关系式。第Ⅱ部分研究了碳酸镍铵溶液中不饱和硫化物在鼓泡塔中的氧化行为,应用返混模型及氧化速度方程,对塔内轴向不饱和硫浓度分布进行了计算,与实验结果比较,两者能基本相符。解析求出了塔内最佳氧化温度,也能与实验结果符合。     

鼓泡塔中液相环流速度分布模型

提出鼓泡塔中液相环流预测的一维流动模型和相应的湍流封闭关系式,并对模型求解方法进行了改进。通过模拟结果和文献数据的对比分析表明,环流速度与塔内液相的流型密切相关。在平稳鼓泡流和剧烈湍流两种流型下,应用本文推荐的涡粘系数关系式可预测液相环流速度的分布,精度令人满意。     

Cavitation Bubble in a Heavy Viscous Liquid

The motion of a cavitation bubble in a heavy viscous liquid is considered. The results of filming of the process are analyzed. A laboratory facility for modeling this phenomenon is described.     

Solid Particle Effects in Centi-scale Slurry Bubble Columns

Both solid particles and column diameter affect the gas holdup and flow regimes in slurry bubble columns, but investigations of the combined effects are not to be found. This study shows the simultaneous impacts on the overall gas holdup and flow regime transitions and determines the dominant effects in slurry bubble columns on the centi-scale containing solid particle concentrations up to 20 vol %. Additional tomography measurements are presented to visualize the gas phase flow and the spatial gas phase distribution in the column.     

Liquid Phase RTD Studies in Sectionalized Bubble Column

The liquid phase backmixing has been reduced significantly by introducing horizontal perforated sieve plates into a 6.2 cm diameter and 77 cm height and in a 20 cm diameter and 90 cm height bubble columns. For the visbreaking operation of the petroleum residue, where the bubble column is used as soaker such a sectionalization has been suggested. The effect of the introduction of different gas quantities at various axial locations has also been studied to check the effect of increasing gas quantity formed in the visbreaking operation. The nonideality in the liquid phase backmixing has been studied by measuring liquid phase RTD and analysed by using one parameter dispersion model. A new parameter FP (flow parameter) has been defined and a correlation to predict liquid phase dispersion coefficient has been developed which covers the entire range of variables used in the present work.     

Turbulent Liquid Flow in a Gas-Liquid Bubble Column

The radial distribution of the axial component of time-average liquid velocity and tur-bulent intensity in a gas-liquld bubble column was investigated experimentally using Laser Doppler Anemometer (LDA). The effects of operating parameters on liquid turbulent intensity are studied and an empirlcal relationship between turbulent intensity and viscosity was established, Such a relationship can he used convenieutly in the calculation of liquid velocity profilea in bubble columns.