共查询到19条相似文献,搜索用时 203 毫秒
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激光全息干涉法测量液相质扩散系数数字图像处理的研究 总被引:2,自引:2,他引:0
用He-Ne激光器、CCD和图像采集系统等仪器设备,搭建了数字激光全息干涉法测量液相质扩散系数的实验系统,并测试获得了浓度为0.33 mol/l KCl水溶液在298.15 K温度下的全息干涉图像,采用了图像增强、全息干涉条纹图再现及相位展开等数字图像处理过程的关键技术对全息干涉图进行处理,得到了相位展开后物光相位差,经换算后获得了该溶液的质扩散系数.为化工工程上研究替代制冷荆急需的质扩散系数测量提供了有效的方法. 相似文献
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通过对相际间力学特性的分析,结合湍流的流动特征,考虑了冰体存在孔隙和毛细作用,给出了临界条件(0℃)湿度差驱动下溶液蒸发冷冻过程中的质扩散分析模型,并对溶液在不同状态下(液态、液固共存和固态)气流界面间的质扩散变化规律进行了研究,结果表明,随着溶液从液态向固态的转变,其表面质扩散系数逐渐减小,即表面质扩散能力逐渐减弱,因此,对于溶液自身蒸发冻结过程而言,为了强化溶液表面的质传递和冻结,应控制冻结过程中溶液表面的结冰状况。这一研究结果为蒸发冷冻传质的研究以及强化蒸发冻结的工程应用提供了理论指导和参考。 相似文献
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介绍数字全息干涉法测量原理.设计并搭建基于数字全息干涉法和新的扩散槽测量质扩散系数的实验系统,并使用此系统测量了浓度为0.33 mol/l的KCl水溶液在温度为291.8、294.7、298.8、299.8、305.4、308.5、315.2 K条件下的质扩散系数,实验结果表明实验值和文献参考值之间相对偏差绝对值的平均数为1.3%,验证了试验系统的精确性和可靠性.最后,在此系统上测量了浓度为0.1 mol/1的蔗糖水溶液在288.15~338.15 K温度范围内的质扩散系数.为测量工程上急需新型燃料替代工质和新型制冷剂替代工质的质扩散系数提供了一种新的有效方法. 相似文献
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用干涉测量法测定了若干条件下蔗糖溶液的扩散系数D。并测定了表面活性剂对D值的影响。当温度为15.5℃(室温)时,浓度为5%的蔗糖溶液的D值为4.62×10~(-6)cm~2/s。相同条件下含有1%表面活性剂的蔗糖溶液的D值为3.73×10~(-6)cm~2/s。结果表明表面活性剂可降低蔗糖溶液的D值。 相似文献
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针对湿度(绝对湿度)差驱动下溶液的蒸发冷冻过程进行了分析研究,在热质平衡理论的基础上,考虑溶液表面冰体的形面变化特征,建立了蒸发冷冻过程中溶液表面冰体生长的热力学非稳态模型,分析了不同蒸发冷冻时刻,气-液界面间湿度(绝对湿度)差、气流速度以及气-液界面间质扩散对溶液表面冰体发展分布的影响,研究表明湿度(绝对湿度)差、气流速度和质扩散系数对溶液的蒸发冷冻作用明显。该理论模型及研究结果为强化湿度差驱动下溶液的蒸发冷冻及工程应用提供了理论指导和依据。 相似文献
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在气相中求取扩散系数的估计法,已有文章介绍。本文就现有的液相中扩散系数的估计法,综合介绍如下。由于液体的理论至今仍未清楚,因此溶质扩散入溶剂的扩散系数,至今亦未得到正确而概括的估计公式。在化工单元操作中,扩散过程日见重要,而扩散系数又为研究扩散过程及设计扩散装 相似文献
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Adsorption breakthrough curves for bisolute systems of dissolved organics on activated carbon are measured in fixed beds.Results for strongly adsorbable species indicate that at low liquid concentrations (X<0.1 mmol/l.) only external mass transfer resistance is rate determining.However, at higher liquid concentrations internal mass transfer becomes increasingly significant. Breakthrough behaviour is predicted using alternatively three different models with different assumptions about diffusion in the liquid filled pores and diffusion on the surface in series with external film diffusion.Multi-solute adsorption equilibria are predicted from single-solute data using the ideal adsorbed solution theory developed by Myers and Prausnitz, while the single-solute equilibria are represented by Freundlich isotherms. The external mass transfer coefficient for each component is calculated by a general correlation for heat and mass transfer in fixed beds. The internal diffusion coefficient for each component is determined in batch reactor tests with the single-solute system.Systematic deviations between measured breakthrough curves and those calculated from different models using only single-solute data are observed in all experiments with mixed solutes if there is significant internal diffusional resistance and marked displacement of one component inside the carbon particles. The deviations may be due to mutual interference of diffusing molecules. A better agreement between calculated and observed breakthrough curves can be obtained using an extended model in which mixture data are required. 相似文献
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利用凝胶内溶质分子向缓冲溶液中扩散的方法,测定了溶菌酶、β-乳球蛋白、卵清蛋白、牛血清白蛋白和γ-球蛋白5种蛋白在聚丙烯酰胺凝胶中的有效扩散系数和分配系数,研究了单体质量浓度、交联度和蛋白分子粒径等因素的影响,讨论了聚丙烯酰胺凝胶中蛋白分子的扩散和分配机制,发现不能用Ogston理论解释聚丙烯酰胺凝胶中蛋白分子的扩散和分配特性 相似文献
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The mathematical formulation of mass transfer in food processes is often based on the diffusion equation with the diffusion coeffcients considered as effective parameters. In some cases, more than one specie can be simultaneously diffusing in opposite directions. Therefore, the movement of one component could affect the movement of the remaining components. The aim of this work is to describe a mathematical procedure to obtain the diffusion coeffcients of different species that simultaneously diffuse in such a situation that each mass flux is affected by the existence of the others. The correspondent microscopic mass balances combined with Fick's law were simultaneously solved using a numerical finite difference method. 相似文献
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The mathematical formulation of mass transfer in food processes is often based on the diffusion equation with the diffusion coeffcients considered as effective parameters. In some cases, more than one specie can be simultaneously diffusing in opposite directions. Therefore, the movement of one component could affect the movement of the remaining components. The aim of this work is to describe a mathematical procedure to obtain the diffusion coeffcients of different species that simultaneously diffuse in such a situation that each mass flux is affected by the existence of the others. The correspondent microscopic mass balances combined with Fick's law were simultaneously solved using a numerical finite difference method. 相似文献
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In this paper, we present a theoretical analysis of the frequency response of a continuous-flow adsorber with periodic modulation
of the inlet flow-rate to measure multicomponent diffusion kinetics in porous media. Micropore diffusion kinetics is assumed
for the intraparticle mass transfer mechanism and three different shapes of microparticle are considered: slab, cylinder,
and sphere. Simulation results for a binary system show that the frequency response of the faster diffusing component is strongly
influenced by the slower component. The out-of-phase characteristic function of the frequency response of the faster diffusing
component shows maximum and minimum points. The deviation between these maximum and minimum values becomes smaller when the
cross-terms of diffusivity go to zero, while the deviation becomes larger when the cross-terms of the adsorption equilibrium
constant go to zero. Contrary to the behaviour of the out-of-phase function of the faster diffusing component, the out-of-phase
function of the slower diffusing component shows no extrema at all. The in-phase characteristic function of the frequency
response of the continuous-flow adsorber is not affected by the overflow parameter. 相似文献
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《分离科学与技术》2012,47(11):1805-1820
Abstract Batch dynamics for the uptake of potassium from crude polyols on Amberlite 252, a strong acid ion-exchange resin, are obtained over a wide range of conditions. Experimental data have been analyzed using a homogeneous model with finite solution volume. An increase of diffusion coefficients with the resin weight used in the purification is observed. An asymptotic maximum value, approaching the value of the diffusion coefficient in bulk solution, is reached for high resin weights or low values of external concentration. The heterogeneous nature of the resin matrix and the large size of the diffusing molecule is proposed as an explanation of this behavior. The proposed purification procedure finds general applicability for other polyol types, being economically and technically feasible. 相似文献
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Mass transport with varying diffusion- and solubility coefficient through a catalytic membrane layer
Mass transport, accompanied by chemical reaction through membrane reactor has been investigated in the case of varying diffusion coefficient and solubility coefficient. In reality, both parameters might depend on the concentration and/or on the inhomogeneity of the membrane layer. General mathematical models were developed to describe the mass transport, taking into account the external mass transfer resistances as well, when the solubility coefficient can vary, e.g. according to the Langmuir–Hinschelwood adsorption theory or when the value of diffusion coefficient depends on the concentration/anisotropy in the membrane. A general solution has been given that can be applied to most of the mathematical functions of the parameters mentioned. The concentration distribution and the mass transfer rate will be given in closed mathematical forms. The value of the mass transfer rates could be strongly altered by the varying diffusion- and/or solubility coefficient. The mathematical model and the effect of the varying parameters have been discussed in this paper. 相似文献
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Conclusions It is proposed to determine the diffusion coefficient by the moving boundary method, without using a solution of the diffusion equation, by studying the finishing stage of boundary movement in appropriate coordinates, which take account of the symmetry and characteristic dimensions of the system.The method is suitable for systems with the symmetry of a plate, a round cylinder, or a sphere, at an arbitrary dependence of the diffusion coefficient on concentration of the diffusing substance.In the case of spinning solutions, the studies may be carried out by observing the movement of the optical boundary in a round drop which is flattened out in the gap between two transparent plates, where, at a certain moment of time, a liquid containing the diffusing substance is introduced.Translated from Khimicheskie Volokna, No. 2, pp. 43–44, March–April, 1984. 相似文献