Drop deformation dynamics and gel kinetics in a co-flowing water-in-oil system.
Drop deformation dynamics and gel kinetics in a co-flowing water-in-oil system.
复制标题
共流油包水系统中的液滴变形动力学和凝胶动力学。
DOI：
10.1016/j.jcis.2005.01.054
复制
发表时间：
2005
影响因子：
9.9
通讯作者：
A. Hermansson
中科院分区：
文献类型：
--
作者：
B. Walther;C. Cramer;Armin Tiemeyer;L. Hamberg;P. Fischer;E. Windhab;A. Hermansson
研究了油包水体系快速连续流动过程中的液滴变形和叠加凝胶动力学。高度单分散的液滴在双毛细管中产生，然后通过狭窄的矩形通道几何形状变形。采用非灵变形实验建立了该过程，并与现有理论进行了比较。随后，加入温度诱导滴凝胶，研究其在短时间尺度和高温梯度下对变形和凝胶动力学的影响。分散相为κ-卡拉胶溶液，外加钠离子和钾离子进行凝胶实验。连续相采用葵花籽油。农灵实验表明，剪切力能使液滴变形为椭球体。即使在水滴变形和流动条件不稳定的情况下，与泰勒的小变形理论的比较也令人惊讶地好。叠加胶凝对变形过程的影响清楚地表明了分散相和连续相流变特性的改变。在冷却连续相时，变形首先增加，直到凝胶形成开始，此时由于液滴粘度/粘弹性的增加，变形明显减少。然后使用水滴变形分析来检测在短至1.8 s的处理时间内高冷却速率下凝胶动力学的差异。
Drop deformation and superimposed gel kinetics were studied in a fast continuous-flow process for a water-in-oil system. Highly monodisperse drops were generated in a double capillary and then deformed passing through a narrowing rectangular channel geometry. Nongelling deformation experiments were used to establish the process and compare it with existing theories. Thereafter, temperature induced drop gelation was included to study its effect on deformation and gel kinetics on short timescales and at high temperature gradients. The disperse phase was a κ-carrageenan solution with additional sodium and potassium ions for gelation experiments. Sunflower oil was used for the continuous phases. Nongelling experiments showed that shear forces are able to deform drops into ellipsoids. A comparison with the small deformation theory by Taylor was surprisingly good even when drop deformation and flow conditions were not in steady state. Superimposed gelation on the deformation process showed clearly the impact of the altered rheological properties of the dispersed and continuous phase. Deformation first increased on cooling the continuous phase until the onset of gel formation, where a pronounced decrease in deformation due to increasing droplet viscosity/viscoelasticity was observed. Drop deformation analyses were then used to detect differences in gelation kinetics at high cooling rate within process times as short as 1.8 s.