甘油水溶液中气液传质过程的研究

对二氧化碳气泡群在不同质量分数的甘油水溶液中的气液传质过程进行了研究。利用二氧化碳探针测定了不同操作条件下二氧化碳的体积传质系数,通过图像处理技术得到了气泡群的界面面积,考察了液相质量分数,气体流量对体积传质系数、界面面积和传质系数的影响。结果表明:体积传质系数均随气体流量的增大而增大,随溶液质量分数的增大而减小。气体流量通过影响界面面积对传质速率产生作用,而甘油水溶液的质量分数对传质速率的影响则归因于黏度对传质系数的影响。     

毛细管中泰勒流液侧传质特性及其强化机理的CFD模拟

采用计算流体力学（CFD）的方法,研究了圆管中泰勒流的液侧传质特性,分析了泰勒气泡上局部传质特性,并研究了气泡上升速度、液膜长度和液栓长度对液膜处和气泡半球帽处平均传质系数的影响。结果表明,泰勒气泡表面局部传质系数存在3个峰值,液膜处的平均传质系数随气泡上升速度增大显著增大,随液膜长度增大而减小,而半球帽处的平均传质系数随气泡速度和液膜长度的增大变化较小,即膜接触时间增加时,液膜处的传质系数降低,而半球帽处传质系数变化较小。另外,引入场协同原则对单元胞内速度场和浓度场进行分析,解释了局部传质特性及强化机理。最后,给出了分别预测短和长膜接触时间下泰勒流液侧体积传质系数的关联式,该式在较宽的管径尺度范围（0.25～3 mm）内的预测误差在±20%以内。     

微通道内气-液传质研究

以CO₂-H₂O为模型体系，实验考察了当量直径为667 μm的单通道和16个并行通道内的气-液传质行为.实验发现，液体表观速度增加，单通道内液侧体积传质系数明显提高;同一液体表观速度下，液侧体积传质系数随气体表观速度增加而增加;在实验数据基础上关联了液侧体积传质系数与气-液两相流参数间的关系.微通道内的液侧体积传质系数较常规尺度气-液接触设备至少高1～2个数量级.并讨论了并行微通道内气-液两相流分配特性对整体传质性能的影响，表明合理设计气、液流动分布结构，可保证微通道内优异的传质特性.     

结构化多相反应器内泰勒流的液侧传质特性

采用定态溶氧法,实验测定了结构化反应器内的液侧体积传质系数.考察了表观气、液速度对液侧体积传质系数的影响,比较了三种不同孔密度的结构化载体(50、100和400 cpsi)内的液侧体积传质系数.结果表明,在实验的操作条件下,床层内的液侧体积传质系数随液体表观速度增大而增大:同-液速下,随气体表观速度增大亦增大.比较不同...     

2,3,6-三甲基苯酚气-液-液氧化反应与传质过程

对2,3,6-三甲基苯酚(TMP)的气-液-液纯氧常压三相氧化反应与传质过程进行了研究。该反应为液膜传质控制的快速反应,氧气消耗速率对原料TMP为1级。在液膜控制条件下探讨了水相体积分数(ε)、搅拌转速(n)、搅拌桨直径(d)和通气量(V)对反应的影响。结果表明,体系在e达到0.58后产生相变,相变后液相体积传质系数随ε变化趋势发生改变,液相体积传质系数(k_L(O₂)a)随n、d、V的增加而增大。综合考虑上述因素对k_L(O₂)a的影响,得到了液相体积传质系数的量纲一关联式,根据关联式计算得到的液相体积传质系数值与实验值接近,平均相对偏差为4.53%,表明关联式拟合效果较好。     

第二液相的加入对气液传质系数的影响

以搅拌罐中的水吸收CO2为研究体系,分别采用异戊醇、苯和正己烷为第2液相,通过实验考察了第2液相的加入对气液传质的影响.实验结果表明:第2液相的加入对气液体积传质系数KLa有很大的影响,且不同的第2液相的影响程度也不同.在一定的操作条件下,KLa均随搅拌速度和第2液相体积分数的增加呈先增大后减小的趋势,随表观气速(在一...     

定-转子反应器气液传质特性实验研究

采用氮气-水脱氧体系,在转子转速为300～1450 r·min-1、水流量为0.75～2.0 m3·h-1、氮气流量为1.5～4.0 m3·h-1的实验条件下,研究了定-转子反应器(RSR)的气液传质特性,初步考察了操作参数及结构参数对RSR气液传质性能的影响.实验结果表明:液体出口氧含量随转子转速(N)、气体流量(Gv)的增加而降低,随液体流量(GL)的增加而升高,液相体积传质系数(kxa) 随N,GL和GV的增加而增大.结构参数对定-转子反应器的气液传质特性具有显著的影响,定-转子反应器内部的转子层数越多,传质单元数NTU越大,传质效果越好.最后采用因次分析法推导出了定-转子反应器液相体积传质系数关联式,且进行了统计检验,所得关联式与实验数据拟合较好.     

微通道内离子液体/乙醇混合溶液吸收CO_2的传质特性

采用高速摄像仪对微通道内离子液体/乙醇混合溶液吸收CO_2的传质行为进行了实验研究。考察了弹状流型下气液两相流量比和离子液体浓度对液侧体积传质系数kLa和液侧传质系数kL的影响。当离子液体浓度不变时,kLa、kL均随气液流量比的升高而增大并逐渐趋于恒定。当液相流量不变时,对于不同浓度的离子液体溶液,液侧体积传质系数kLa和液侧传质系数kL随气液流量比的变化曲线出现了交叉点。在交叉点之前,kLa和kL均随着离子液体浓度的增大而减小;在交叉点之后,kLa和kL均随着离子液体浓度的增大而增大。提出了用于预测液侧体积传质系数kLa的新的量纲1经验关联式,预测效果良好。     

循环浆态床气液传质系数的研究

以空气-水-玻璃微珠和空气-石蜡油-玻璃微珠两种三相系统为研究对象,在常温常压下分别考察了液体介质的粘度等物性因素,表观气速、固含率、液体循环量等操作因素,气体分布器、分隔板等结构因素对循环浆态床反应器气液传质特性的影响.实验结果表明,气液传质系数随表观气速的增加而增加,随液体粘度和固含率的增大而减小,当表观气速和固含率增加到一定程度后,传质系数趋于稳定;低气速下,玻璃烧结板的传质效果较好,而较高气速时,多孔板和新型锐孔分布器的传质效果较好;分隔板能显著增大气液传质系数.对多孔板分布器实验数据进行了拟合,得出气液传质系数的经验关联式,关联式计算值与实验结果吻合良好.     

板上充气状态下立体传质塔板液体提升量研究

以空气-水为实验物系,在直径为600 mm的实验塔内,通过向板上液层中充气来模拟板上的泡沫状态,测定了立体传质塔板CTST液体提升量的变化情况。考察了不同操作条件下板上气体体积分数对液体提升量的影响,并由实验数据拟合出板孔动能因子、板上液层气体体积分数、板上清液层高度对相对液体提升量影响的关联式。结果表明:相对液体提升量随着板上液层中气体体积分数的增加而降低;气体体积分数相同时,相对液体提升量随着板上清液层高度的增大而增加、随板孔动能因子的增大而减少。     

The influence of molecular diffusion on mass transfer between turbulent liquids

The influence of molecular diffusion on liquid—liquid mass transfer in a stirred transfer cell has been found by measuring the rates transfer of helium and iso-butane from water to toluene and dekalin. These solutes have very different diffusion coefficients, their presence does not alter the physical properties of the liquids and, because their equilibrium distributions strongly favour the organic phases, the water phase mass transfer coefficient could be determined and was found to depend on the square root of the diffusion coefficient.The results are compared with the predictions of a model for liquid—liquid mass transfer under turbulent conditions, based on the approach of an eddy to the interface being restrained by interfacial tension and gravitational forces and taking into account eddy pressure fluctuations in both phases. This model provides a correlation for these results, as well as water phase mass transfer coefficients for the transfer of iso-butane from water to n-octanol, and previous stirred transfer cell results.     

高含硫天然气管道泄漏数值模拟

高含硫天然气管道经长期的内外腐蚀,经常发生泄漏事故.为了减少和降低天然气管道泄漏事故对人的危害,对甲烷及硫化氢的扩散规律进行研究日趋重要.利用计算流体力学的方法,采用仿真软件对高含硫天然气架空及埋地管道穿孔泄漏后的甲烷、硫化氢气体的扩散进行了数值模拟.架空管道泄漏初期为体积分数等值线呈对称分布的射流,泄漏至60s后无爆...     

超稠油埋地热输管道保温失效的数值模拟

针对超稠油埋地管道高温输送的特点,建立了热输管道的稳态传热模型,考虑了自然对流换热对温度场分布的影响,利用CFD软件对管道保温失效前后的温度场进行了数值模拟并进行了对比分析,进而为管道安全检测提供一定的理论指导。     

热油管道横向温度场分布理论研究

热油管道输送过程中,管道温度场的分布是不断变化的。本文根据确定临界状态,分析输油管道周围土壤温度场分布,研究埋地热油管道的周围土壤温度分布曲线。     

煤层气集输管路三种排液方式模拟研究

为了比较煤层气集输管路三种排液方式的排液效果,以相态计算与两相流计算为基础建立煤层气集输管路排液模拟模型。利用该模型仿真模拟了清管排液、低点安装分水阀、起点空冷预脱水三种排液过程。分析了排液效果。通过模拟结果发现:清管操作对管内液体的清除效果最好,可以有效降低管路沿线的液量;低点安装分水阀操作对装置所在位置及附近区域的效果是连续的,但对管路全线液量控制效果有局限性;起点空冷预脱水操作对管内液体的控制主要体现在有效的控制管内液体累积速度方面,对管路积液量的控制效果较为持久。     

Internal Mass Transfer during Isothermal Drying of a Porous Solid Containing Multicomponent Liquid Mixtures

Internal mass transfer in a porous solid partially saturated with multicomponent liquids has been experimentally and theoretically studied. Isothermal drying experiments were performed using a jacketed wind tunnel where the transient composition profiles and total liquid content of a cylindrical sample were determined. Sand samples wetted with the ternary liquid mixtures water-methanol-ethanol and 2-propanol-methanol-ethanol were dried at two different initial compositions and temperatures. A mathematical model including mass transfer by capillary movement of the liquid and interactive diffusion in both gas and liquid phase was developed. To simulate the capillary movement of liquid mixtures, parameters experimentally determined for single liquids where weighed according to liquid composition. A fairly good agreement between theoretical and experimental liquid composition profiles was obtained provided that axial dispersion is included in the model.     

Internal Mass Transfer during Isothermal Drying of a Porous Solid Containing Multicomponent Liquid Mixtures

Abstract

Internal mass transfer in a porous solid partially saturated with multicomponent liquids has been experimentally and theoretically studied. Isothermal drying experiments were performed using a jacketed wind tunnel where the transient composition profiles and total liquid content of a cylindrical sample were determined. Sand samples wetted with the ternary liquid mixtures water-methanol-ethanol and 2-propanol-methanol-ethanol were dried at two different initial compositions and temperatures. A mathematical model including mass transfer by capillary movement of the liquid and interactive diffusion in both gas and liquid phase was developed. To simulate the capillary movement of liquid mixtures, parameters experimentally determined for single liquids where weighed according to liquid composition. A fairly good agreement between theoretical and experimental liquid composition profiles was obtained provided that axial dispersion is included in the model.     

Passage of a bubble through the interface between a shear-thinning heavier liquid and a Newtonian lighter liquid

Abstract

Numerical simulations are carried out to study the phenomenon of passage of a bubble through the interface between two initially quiescent liquids. The heavier liquid is a viscous shear-thinning liquid whereas the lighter liquid is a viscous Newtonian liquid. The computational model, which is based on axisymmetric computational domain and VOF (volume of fluid) method, is validated by using the data reported in literature. The validated computational model is then used to perform parametric analysis to understand the effects of bubble diameter, interfacial tension between the two liquids and flow index of the heavier liquid on the drainage time, drainage height, retention time and retention height of the bubble at the liquid–liquid interface. Finally, correlations for retention time and retention height are proposed.     

Concentration-dependent molecular diffusion coefficient of gaseous ethane in liquid toluene

We report new experimental data on concentration-dependent molecular diffusion coefficient of ethane in toluene at temperatures ranging from 21 to 125°C and pressures up to 4.14 MPa. An analytical model has also been developed for estimation of the diffusion coefficient utilizing the experimental data of the interface velocity as a result of swelling and the rate of gas dissolution in the liquid phase. It is shown that the diffusion coefficient of ethane in toluene is dependent on the initial mass fraction of the gaseous component in the liquid. In addition, the effect of concentration dependency of the molecular diffusion coefficient on diffusive mass flux is quantified. The results reveal that the assumption of a constant diffusion coefficient introduces ~10–60% error in calculation of diffusional mass transfer flux. The developed methodology finds application in estimation of the concentration-dependent molecular diffusion coefficient of gases in liquids.     

Liquid—liquid mass transfer in systems agitated by submerged jets

Mass transfer across a plane interface has been investigated for liquid—liquid systems, with the liquid phases agitated by vertically opposed, submerged jets, one in each phase. Mass transfer coefficients were determined for the systems ethyl acetate—water and butanol—water, and for the transfer of dissolved helium between water and toluene, and toluene between toluene and water. The latter two solutes provided a wide range of molecular diffusion coefficients. When turbulent eddies penetrated to the interface the mass transfer coefficients were found to be proportional to D^0.5, and could be represented by the Levich-Davies mass transfer model for mass transfer between turbulent liquids. The characteristic turbulence velocities in this model were related to the velocities of the liquids from the jet nozzles, and to the equipment dimensions (e.g. the distances of the jets from the interface, the radius of the vessel and the diameters of the jet nozzles) by an expression based on the hydrodynamic behaviour of jets.For the low interfacial tension system butanol—water, a flat disc had to be placed in the interface at the region of jet impingement, to prevent disruption of the interface, but, even so, only a limited range of jet flow rates could be used. Only at the highest flow rates were turbulent conditions obtained, and most of the experimental mass transfer coefficients for this system were between the values predicted by the Levich-Davies model and the Levich “three-zone” model for boundary layer flow.