共查询到17条相似文献,搜索用时 265 毫秒
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通过纹影系统对乙醇溶液解吸CO2的过程进行了实验研究,液层自由界面的俯视纹影图记录了对流结构的演化过程,并捕捉到了Marangoni对流结构的初始形态。相应的胞型结构因发展空间的限制,由初始的近圆形逐渐变成了多边形结构。利用纹影图片的灰度分布信息,对单个胞型结构的出现、发展及分裂阶段进行了定性分析,发现界面非均匀传质所引发的界面对流在其胞型发展的过程中将会导致界面的变形。湍动的后期,液层表面将布满多边形结构,且胞型结构基本保持不变。相应纹影图片的颜色差异随解吸的进行逐渐减小,即随着传质推动力的减小,湍动强度也将减弱。 相似文献
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采用光学纹影系统对乙醇和水双组分解吸传质过程的对流结构的界面湍动进行了定性观察和定量分析。建立了一套水平非稳态气液传质设备,试验观测了乙醇和水体系中液相组分向气相传质过程的Marangoni界面对流结构。还通过对传统纹影方法的改进,对乙醇解吸传质过程的浓度(本文用质量分数表示)梯度场进行了定量测量。定量分析表明乙醇和水系统解吸过程中,引发界面湍动的原因是局部较大的表面张力梯度。定量分析的结果很好的解释了伴随Marangoni效应的传质过程的混乱的对流结构,为进一步对界面湍动现象的分析提供了帮助。 相似文献
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双光路纹影仪观察气液传质界面湍动现象 总被引:2,自引:1,他引:1
建立了双光路纹影仪实验系统,并利用双光路纹影仪,同时从垂直和平行于界面两个方向对氯苯吸收、解吸CO2的传质对流结构进行了观察,发现在氯苯吸收CO2时,没有明显的对流结构,只是在垂直界面的纹影图像中观察到逐渐变粗的暗条纹。在氯苯解吸CO2时,在垂直和平行于界面两个方向都观察到了明显的对流结构,在垂直界面的纹影图像中开始时出现分层现象,随着解吸的进行,对流加剧,分层现象被破坏;平行界面方向的对流结构发展较快,优先在平行界面的纹影图像中观察到明显的对流结构。由于传质的热效应,两个方向的对流结构都有向中心运动的趋势。实验表明,双光路纹影仪实验系统能观察界面传质对流过程的三维变化,可深化对界面传质对流过程的认识。 相似文献
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通过纹影光路观察了特定气液传质装置中乙醇吸收CO2过程所引发的Rayleigh对流在垂直界面方向上的发展过程。随着溶质吸收的进行,液层的流体稳定性变弱,扰动加剧气液界面失稳并发生湍动,进而发展为羽状流并逐步向液相主体发展,在此过程中伴随着对流胞的融合与增长。液层的浓度分布可通过对相应液层纹影图像进行定量分析获得。液层浓度分布和瞬时传质系数变化表征了Rayleigh对流的引发与发展及其对传质过程的强化效果,界面浓度分布及临界Rayleigh数解释了非均匀传质对湍动的引发机理。羽状流将高浓度液体快速带入主体,加速了近界面液层与主体液层的混合,增强了气液传质。 相似文献
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《化工学报》2016,(11)
通过纹影光路观察了特定气液传质装置中乙醇吸收CO2过程所引发的Rayleigh对流在垂直界面方向上的发展过程。随着溶质吸收的进行,液层的流体稳定性变弱,扰动加剧气液界面失稳并发生湍动,进而发展为羽状流并逐步向液相主体发展,在此过程中伴随着对流胞的融合与增长。液层的浓度分布可通过对相应液层纹影图像进行定量分析获得。液层浓度分布和瞬时传质系数变化表征了Rayleigh对流的引发与发展及其对传质过程的强化效果,界面浓度分布及临界Rayleigh数解释了非均匀传质对湍动的引发机理。羽状流将高浓度液体快速带入主体,加速了近界面液层与主体液层的混合,增强了气液传质。 相似文献
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通过纹影光路,捕捉到低表面张力溶质从水中解吸导致的气液界面失稳过程及后续的对流结构图像.乙醇、异丙醇和丙酮水溶液中的现象相似:传质开始进行时,界面出现一个迅速变大的湍动区,湍动区扩张的同时,其边缘区域产生很多圆形的小胞,这些小胞逐渐演化成多边形,短暂的界面失稳过程之后,界面对流结构逐步发展为环形;但在乙酸乙酯体系中,界面对流结构一直都是团状的,而且湍动强度更为剧烈.结果表明,界面对流结构特点和剧烈程度取决于实验条件和体系的物理性质. 相似文献
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单组分扩散过程中界面湍动对流结构的观察 总被引:1,自引:0,他引:1
利用激光纹影仪从垂直和平行于界面两个方向对静止和流动乙醇吸收、解吸C02的传质对流结构进行了观察,发现在液相主体中明显存在传质导致的液体对流现象,同时发现对流结构在液相流动方向取向具有优先性。研究界面对流对增大传质速率,探索微观传质机理和寻求强化传质途径具有理论和实际意义。 相似文献
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In gas-liquid mass transfer processes,interfacial turbulence may occur due to the surface tension gradient and the density gradient produced by mass transfer near the interface.The interfacial turbulence can enhance the mass transfer since it intensifies the movement of interfacial fluid.By means of the shadowgraph optical method,the interfacial turbulence patterns vertical to the interface were observed directly in the volatilization process of binary systems.The images of the amplified interfacial turbulence showed the variation of concentration and the fluid movement under the interface.Two patterns of interfacial turbulence were observed in the experiments:plume and vortex.With the plume,the interfacial fluid moved slowly and penetrated the liquid deeply.With the vortex,the interfacial turbulence occurred in the vicinity of the liquid interface and the fluid moves quite fast.A qualitative analysis was carried out based on the mechanism of Rayleigh-Bénard convection induced by density gradient and Marangoni convection induced by surface tension gradient. 相似文献
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In gas-liquid mass transfer processes,Marangoni convection may occur due to the surface tension gradient produced by mass transfer near the interface.With a falling soap film tunnel and the Schlieren optical method,the Marangoni convection patterns along the film surface were observed directly in the desorption process of acetone from the falling soap film.The Schlieren images showed the regular roll convection in the thin falling soap film during the acetone desorption.The hydraulic characteristics were determined experimentally by measuring the variation of acetone concentration in the film and the surface tension of the soap liquid.The results show that the acetone concentration gradient vertical to the falling direction is very small because the thickness of the soap film is in the order of 10-6 m.The variation of acetone concentration along the falling film is large,so there is a significant surface tension gradient,resulting in the Marangoni roll convection.The experimental results and a qualitative analysis may be helpful to understand the mechanism of Marangoni convection near the interface in the mass transfer. 相似文献
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针对乙醇吸收CO2过程中,由CO2通过界面向液体乙醇传递所导致的Rayleigh对流现象的模拟,建立了二维格子Boltzmann方法(LBM)。采用浓度分布函数和流体质点密度函数的双分布模型格子Boltzmann方法,同时引入由浓度差导致的重度差作为外加力,实现了流体中浓度场与速度场的模拟。应用所建立的LBM方法,对界面具有多个离散CO2扩散源的二维区域液相Rayleigh对流现象进行了模拟,结果显示,模拟得到的浓度分布结构与文献中实验结果相一致。通过考察Rayleigh对流和浓度分布结构,分析了Rayleigh对流存在条件下的传递规律。通过采用LBM方法对浓度场模拟可以定量给出液相界面瞬时传质通量。计算结果表明,瞬时传质通量随时间的增长先增加后减小,这种变化与相似文献
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应用二维非稳态格子Boltzmann方法研究了异丙醇-水溶液和丙酮-乙酸乙酯溶液解吸过程中Rayleigh对流的临界开始时间、流动特征及其对界面传质的影响,并与相关文献对比. 结果表明,临界开始时间随界面浓度增加呈先缓慢增大再迅速增大最后趋于稳定的变化趋势. Rayleigh对流结构经历了从有序到无序的发展过程,是不断更新的耗散结构. Rayleigh对流主要作用于液相主体,使液相主体具有较大的湍动速度(10-4~10-3 m/s). 液相主体中存在许多循环流动,促进了界面更新及界面与液相主体之间液体的交换与混合. 传质增强因子(介于2~6之间)表明Rayleigh对流能有效提高解吸过程传质速率,强化界面传质过程. 相似文献
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PD Dr.‐Ing. habil. S. Raatz Dr.‐Ing. P. Klapper Prof. Dr.‐Ing. habil. G. Härtel 《化学,工程师,技术》2010,82(10):1705-1711
The interfacial tension is a material parameter describing the interface between two fluid phases. It is also a changing physical value in mass transfer processes beyond equilibrium. Thus, the measurement of change in interfacial tension characterizes adsorption and mass transfer processes at liquid‐liquid interfaces. The units of a pendant drop tensiometer can represent a mini mass transfer cell. 相似文献
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By using a hybrid lattice-Boltzmann–finite-difference method (hybrid LBM–FDM method), three-dimensional simulations of solutal interfacial convection were conducted for the process of CO2 absorption into ethanol. A self-renewal interface model is adopted as an interfacial perturbation model. The simulation results revealed some three-dimensional features of the induced interfacial convection, such as the development of diverging cellular flow and Rayleigh plume-like convection in liquid phase. The concentration distribution of the simulation result is validated and found to be in wel agreement with the Schlieren visualization results qualitatively. Addi-tionally, the mass transfer enhancements by interfacial convection were investigated via both simulation and experiment for the absorption process, and the mass transfer is shown to be enhanced by the interfacial convec-tion by about two-fold comparing with that by diffusion. 相似文献