Measurement and modeling of the flow behavior of aqueous foams using a recirculating pipe rheometer
Measurement and modeling of the flow behavior of aqueous foams using a recirculating pipe rheometer
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DOI：
10.1016/j.colsurfa.2005.01.012
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发表时间：
2005-08-01
影响因子：
5.2
通讯作者：
Moan, M
中科院分区：
文献类型：
--
作者：
Herzhaft, B;Kakadjian, S;Moan, M
描述了与泡沫生成系统相关联的再循环管道流变仪。除了通过直管测量体积流量和压降外，该系统还可以同时在线测量泡沫质地、泡沫密度、温度和在线静压。使用该设备，我们测量了通过添加表面活性剂稳定的泡沫在类似于10至10（3）s（-1）的剪切速率范围内的稳态流动曲线。数据已针对泡沫在管壁处的明显滑动进行了校正。泡沫的流动行为被检查作为气体体积分数φ（或泡沫质量）的函数，范围从20至85%，在不同的静压和各种浓度的添加的表面活性剂。体积分数高达phi = 50%的泡沫包含孤立的球形气泡。它们的粘度是牛顿型的，并且由体积分数而不是由气泡尺寸分布控制，如对于中等浓度的乳液与Taylor-Mooney粘度模型的预测的良好一致性所示。对于高体积分数泡沫（φ>= 60%），气泡被薄液膜分离。这些泡沫的粘度/剪切应力曲线显示出超出表观动态屈服应力的严重剪切变稀行为以及向高剪切应力渐近线的趋势。它们的剪切应力/剪切速率等效曲线可以用Herschel-Bulkley模型拟合。经验泡沫和乳液模型，其中包括物理参数的预测，也进行了分析。由瓦尔科和Economides提出的体积均衡方法假定一个合适的参数是与泡沫压缩性有关的膨胀比，但无论流动曲线的类型如何，该方法都不能将稳态流动曲线简化为主曲线。在另一方面，该模型描述的剪切粘度作为毛细管数的函数，被发现足以描述具有屈服应力的泡沫体的行为，但只有高达75%的体积分数。最后，考虑了Prud'homme和Otsubo提出的高浓度乳液的标度分析，我们证明，在固定的高体积分数下，对于不同浓度的添加表面活性剂获得的剪切粘度与界面张力与Sauter直径的比率成比例，反映了总界面面积的重要性。(c)2005 Elsevier B. V.保留所有权利。
A recirculating pipe rheometer associated with a foam generation system is described. In addition to the measurement of the volumetric flow rate and the pressure drop through straight pipes, the system allows simultaneous online measurement of the foam texture, foam density, temperature and inline static pressure. With this equipment, we measured steady-state flow curves of foams, stabilized by addition of a surfactant, over a shear rate range of similar to 10 to 10(3) s(-1). The data have been corrected for the apparent slip of the foam at the pipe wall. The flow behavior of foams is examined as a function of the gas volume fraction phi (or foam quality) ranging from 20 to 85%, at different static pressures and for various concentrations of the added surfactant. Foams at volume fractions up to phi = 50% contain isolated spherical bubbles. Their viscosity is Newtonian and governed by the volume fraction and not by the bubble size distribution, as shown by the good agreement with the predictions of the Taylor-Mooney viscosity model for moderately concentrated emulsions, For high volume fraction foams (phi >= 60%), the bubbles are separated by a thin liquid film. The viscosity/shear stress curves of these foams show a severe shear-thinning behavior beyond an apparent dynamic yield stress and a tendency to a high shear stress asymptote. Their shear stress/shear rate equivalent curves are adequately fitted by the Herschel-Bulkley model. The predictions of empirical foam and emulsion models, which incorporate physical parameters, are also analyzed. The volume equalization method, proposed by Valko and Economides, which assumes that a suitable parameter is the expansion ratio related to the foam compressibility, fails to reduce the steady-state flow curves to a master curve, whatever the type of flow curve. On the other hand, the model of Princen and Kiss, which describes the shear viscosity as a function of the capillary number, is found adequate to describe the behavior of foams having a yield stress, but only for volume fractions up to 75%. Finally, the scaling analysis proposed by Prud'homme and Otsubo for highly concentrated emulsions is considered, We demonstrate that, at a fixed high volume fraction, the shear viscosities obtained for various concentrations of added surfactant scale with the ratio of the interfacial tension to the Sauter diameter, reflecting the importance of the total interfacial area. (c) 2005 Elsevier B.V. All rights reserved.