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Marangoni效应对填料塔精馏传质过程的影响 总被引:4,自引:1,他引:4
通过 4种正体系、 5种负体系的精馏实验 ,考察了Marangoni效应对填料塔中传质过程的影响。结果表明 :正体系的气相体积总传质系数KGa与组成无关 ,仅受气相流量 qG 的影响 ,可用关联式KGa =AqGB,和B =0 .94± 0 .0 4表示 ;而对负体系 ,由于Marangoni效应的存在 ,顺着液相流动方向 ,KGa逐渐减小。其关联式为KGa =AqGBMsC,B =1.0 5± 0 .0 4,C =0 .3± 0 .0 5 ,该式的平均误差约为 6%。 相似文献
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通过实验测量不同醇类表面活性剂在全浓度范围下的气泡聚并时间,进而研究表面活性剂种类及其浓度对气泡聚并的影响。结果表明,加入醇类表面活性剂后,相比于纯液体体系,气泡聚并受到明显抑制,液膜更加稳定,气泡聚并时间延长。低浓度范围内,气泡聚并时间随着表面活性剂浓度的升高显著增长,而在高浓度范围内,气泡聚并时间随着浓度的升高显著缩短。醇类表面活性剂对气泡聚并的抑制作用存在临界浓度。实验测得异丙醇和乙醇对气泡聚并抑制作用最强时对应的临界摩尔分数,分别为0.0030和0.0096。此外,对比不同醇对气泡聚并的抑制作用,发现长碳链醇由于更强空间力而具有更强的抑制气泡聚并能力。最后根据Andrew模型分析表明,表面张力梯度是体现表面活性剂抑制气泡聚并能力的主要因素之一。 相似文献
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塔板上气泡直径的模拟计算 总被引:1,自引:0,他引:1
塔板上气液泡沫层传质面积对传质速率影响很大.传质面积由气泡的直径、大小分布和浓度所决定.气泡大小受塔板上流体力学状况影响,要对塔板上的气泡直径和分布进行可靠的模拟计算,就要对板上泡沫层的流体力学状况有着透彻了解,而板上流体力学状况十分复杂,因此,气泡直径的模拟计算和测定都很困难.气泡直径的模拟计算有两类方法--局部法和总体法.先简介局部法模拟计算气泡直径方法,然后进行总体法模拟计算气泡直径研究.通过建立一个数学模型,对塔板上泡沫层的气泡直径进行模拟计算,模拟计算结果和文献报道的实验测定结果基本一致. 相似文献
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<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. 相似文献
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对2个小气泡或小液滴之间的聚并进行了动力学分析,并考虑范德华力的影响,得到了界面无切向运动时气泡或液滴聚并所需时间与气泡直径、流体主体和界面性质的关系。 相似文献
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气液界面Marangoni效应对传质系数的影响 总被引:1,自引:0,他引:1
在气液相际传质过程中,界面Marangoni湍动会对传质过程产生重要的影响,为此,建立了一套气液接触传质设备,以使得通过N2与异丙醇稀溶液逆流接触将液体中使表面张力降低的溶质解吸出来,从而引发Marangoni湍动,提高传质速率。发生Marangoni对流时,液相的传质系数比只依靠扩散传质而不考虑Marangoni效应时大,因此引出增强因子F这一概念,通过计算F的值即可判断Marangoni效应对传质速率影响的程度。提出了一个包括Marangoni准数的计算传质系数关联式,其计算结果与实验结果相符. 相似文献
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An experimental investigation was made to measure interfacial area, a, and liquid‐side volumetric mass transfer coefficient, kLa, in a downflow bubble column by chemical methods viz., absorbing CO2 in aqueous sodium hydroxide and sodium carbonate/bicarbonate buffer solution respectively. The effect of gas and liquid flowrate and nozzle sizes on a and kLa were investigated. The experimental data obtained in the present system were analyzed and correlations were developed to predict a and kLa in terms of superficial gas velocity. The variation of a and kLa with specific power input were shown in graphical plot and compared with other gas‐liquid systems. 相似文献
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This paper focuses on the mechanism of interfacial mass transfer of a single bubble, based on the chemical potential driving force, an approach for calculating interfacial concentration in practical process is proposed. The absorption processes of bubble under both quiescent and mobile conditions are analyzed and discussed respectively. For a stationary absorption, only in the case of liquid bulk concentration near saturated value, the interfacial concentration could close to the equilibrium value ; For a moving bubble, under ordinary operating condition (Yo〉l), the interfacial concentration is far from its equilibrium. Only under bulk concentration near saturated value or a smaller Yo(Yo〈0.1) which may involve the complication of additional resistance at interface induced by surface contamination or surfactant added, the interfacial concentration could be approximate to equilibrium value. The interfacial concentration close to the interface on liquid side for a single CO2 bubble absorbed by methanol is measured using a modern optical instrumentation in which the laser holographic interference method is adopted with a real-time and amplification technique. Experimental results show that the interfacial concentration decreases significantly with increasing Re and is far from the equilibrium one in a larger Re range. Experiments validate the proposed model. 相似文献
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For the mass transfer to single drops during the stage of steady buoyancy-driven motion, experimental measurement is complicated with the terminal effect of additional mass transfer during drop formation and coalescence at the drop collector. Analysis reveals that consistent operating conditions and experimental procedure are of critical significance for minimizing the terminal effect of drop coalescence on the accuracy of mass transfer The novel design of a totally-closed extraction column is proposed for this purpose, which guarantees that the volumetric rate of drop phase injection is exactly equal to that of withdrawal of drops. Tests in two extraction systems demonstrate that the experimental repeatability is improved greatly and the terminal effect of mass transfer during drop coalescence is brought well under control. 相似文献
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以分子热力学为基础 ,对气体吸收过程进行了理论分析 ,导出了传质通量的数学表达式。根据该文分析 ,气液界面传质的源动力来自界面处气液两相的不平衡 ,即只要有传质发生 ,液相界面处的浓度就不会达到与气相呈平衡的浓度。对于气相阻力可以忽略的吸收过程 ,两相传质速率的大小主要取决于液相的溶质界面浓度和液膜厚度 ,影响溶质界面浓度和液膜厚度的主要因素是近界面液相侧的流场分布。利用近界面浓度与液膜厚度的激光测定结果 ,计算了甲醇、乙醇及正丙醇吸收CO2 气泡的传质通量 ,计算结果与实验值吻合良好 相似文献