Characterization of rheological properties of systems containing sugar substitutes and carrageenan

The effects of addition of κ-carrageenan to solutions containing 40% (w/w) sugar substitute on the rheological properties of these systems were investigated at 25 °C using a rotational viscometer at rotational speeds of 6, 12, 30, and 60 rev min⁻¹. The flow behaviour of the solutions was adequately described by the power law model with or without yield stress. The consistency index ( K ) and the flow behaviour index ( n ) were determined from shear stress vs. shear rate data. The flow parameters of the solutions depended on the carrageenan concentration. The apparent viscosities of the systems decreased with increasing shear rate, indicating pseudoplastic behaviour. The final carrageenan concentration was found to be an effective factor controlling the degree of sliminess of the model food systems studied.     

Gas-liquid mass transfer in three-phase fluidized beds with viscous pseudoplastic liquids

Liquid phase volumetric mass transfer coefficients for oxygen were determined in three-phase fluidized beds of 8 mm glass spheres fluidized by a cocurrent flow of air and pseudoplastic polysaccharide solutions (carboxymethyl cellulose, xanthan). A semi-theoretical relation for the effective shear rate was suggested. The mass transfer coefficients could be correlated, together with literature data for particle diameters of 3 mm and 5 mm in other liquids, using the terminal velocity as the particle-specific property.     

A Unified Model for the Mixing of Non‐Newtonian Fluids in the Laminar,Transition, and Turbulent Region

Summary: Non‐Newtonian fluid behavior has significant influence on quantities in chemical engineering like power input, mixing time, heat transfer etc. In the laminar flow region, the concept of effective viscosity by Metzner and Otto is well established. In the transition region between laminar and turbulent flow, the existing concepts use three and even more empirical parameters to determine the specific power input. Here, a unified and general but simple approach is introduced to calculate the power input for shear thinning fluids over the whole flow region using just one empirical parameter. The Metzner‐Otto relation is obtained as a limiting case for the laminar region. The empirical parameter of the new approach is related to the Metzner‐Otto constant. The concept is validated for eight different stirrer systems. Mixing time and maximum shear rate and heat transfer can also be calculated using this approach. The new concept presented should also be applicable for other apparatuses, e.g., static mixers.

Comparison of experimental data and a curve calculated according to the new method (solid line).     

Rheological characteristics of foamed gel for mine fire control

Foamed gel as a new type of fire extinguishing material is used to prevent the spontaneous combustion of coal. In order to make a comprehensive study on rheological characteristics of foamed gel for mine fire control, by using type NDJ‐5s digital viscometer, the factors such as mass concentration of the mixture mixed by thickener and crosslinker, foaming multiple, added salts (NaCl, CaCl₂, AlCl₃), pH value and temperature having influences on the rheological properties of foamed gel have been investigated in this paper. It can be found that foamed gel shows the characteristic of non‐Newtonian fluids and has shear‐thinning properties. With increasing of mass concentration of the mixture, the thixotropy response becomes more significant. When the foaming multiple reaches 20, the apparent viscosity gets the maximum value. The obvious viscosity characteristic of ‘polyelectrolyte solution’ is observed in aqueous salt solutions when added salts are put into the solution. Under different conditions of pH values, foamed gel has higher sensitivity to acid than alkaline. Zero shear viscosity, depending on temperature, decreases with the temperature increasing. Meanwhile, the fire performances of foamed gel are studied experimentally and theoretically. Copyright © 2014 John Wiley & Sons, Ltd.     

槐花蜂蜜的流变性能

采用ＮＤＪ－７９型旋转粘度计测定了不同水份含量的山东槐花蜜在３０℃～７０℃温度范围内的流变特性，并考察了水份含量和温度对其粘度的影响规律，回归出了二者对粘度影响的经验方程。结果表明在所考察的范围内，槐花蜜为假塑性流体，符合幂律方程的τ＝Ｋγｎ；温度对其表观粘度的影响符合Ａｒｒｈｅｎｉｕｓ方程；水份含量对槐花蜜的表观粘度和流体性质的影响显著，含水量越少，非牛顿性越显著；反之牛顿性越显著。表观粘度与温度和水份符合经验式ηａ，１００＝２．８４９５２×１０－１０×ｅｘｐ（４９７６．４３／Ｔ）×Ｗ－３．０２１７２。据此可在一定范围内预测蜂蜜的粘度和流变特性，为工业加工生产提供了一定的理论依据     

白乳胶与硅溶胶复配粘结剂对铸铁件消失模铸造涂料性能的影响

为改善铸铁件消失模铸造涂料的性能,分别研究了单一粘结剂白乳胶与硅溶胶,以及二者复配溶液对涂料性能的影响。结果表明,采用单一粘结剂,无论是白乳胶还是硅溶胶,其加入量在2%~3%时,都能较好地满足涂料的使用要求。当二者进行复配后,白乳胶与硅溶胶的配比为2:3时,涂料的综合性能要比单一使用粘结剂更优,其悬浮性、触变性更好,流杯粘度、涂层强度和透气性适宜,而且涂挂性和高温抗裂性良好,是带有一定屈服值的较理想假塑性流体。     

聚合物在环形空间中雷诺数和临界流速、流量的计算

从非牛顿流体运动方程和幂律流体本构方程出发，导出了聚合物在环形空间中精确的流量，压差表达式，并由此得出雷诺数的计算公式；根据实验数据给出了聚合物在环形空间中流动的临界雷诺数，临界平均流速和临界流量的计算公式，为三次采油中的单管分层注聚合物提供了理论依据。     

RHEOLOGICAL BEHAVIOR OF CONCENTRATED INULIN SOLUTION: INFLUENCE OF SOLUBLE SOLIDS CONCENTRATION AND TEMPERATURE

Inulin is a storage polysaccharide present in more than 30,000 vegetable products, including chicory roots, that are considered suitable for industrial application. The objective of this work was to evaluate the influence of temperature and the soluble solids concentration on the rheological behavior of a concentrated inulin solution obtained from a centrifugation process from chicory roots, after freezing at − 24C. For all the evaluated soluble solids concentrations, inulin solutions showed a rheological behavior of a highly pseudoplastic fluid, with high resistance to flow at low strain rates followed by a breakdown of the structure when the shear rate increased. The effect of temperature on the apparent viscosity of inulin solutions can be represented by the Arrhenius equation. The rheological behavior of inulin solutions can be represented by the Herschel–Bulkley, Casson, Cross and Power Law equations, where the consistency index increases as temperature rises and the soluble solids concentration as well.

PRACTICAL APPLICATIONS

The main objective of this work was to analyze the rheological behavior of a concentrated inulin solution obtained from chicory roots, to check the possibility of its application to obtain powder inulin.
The concentrated inulin solution was obtained by diffusion in hot water, followed by concentration by evaporation and phase separation conducted by lowering the temperature (−24C) and centrifugation at a velocity of 10,000 rpm for a time interval of 15 min. However, this solution is still going to be processed. Therefore, it is important to know its rheological behavior.
The influence of temperature and the soluble solids concentration on the rheological behavior of the concentrated inulin solution was also studied.     

Rheological and viscoelastic properties of colloidal solutions based on gelatins and chitosan as affected by pH

The objective of this study was to evaluate the influence of pH on rheological and viscoelastic properties of solutions based on blends of type A (GeA) or type B (GeB) gelatin and chitosan (CH). Solutions of GeA, GeB, CH, GeA:CH, and GeB:CH were prepared in several pH (3.5–6.0) and analyzed for determination of zeta-potential. Rheological analyses (stationary and dynamic essays) were carried out with blends allowing to study the effect of pH on shear stress, apparent viscosity, loss (G”) and storage (G’) moduli, and angle phase (Tanδ). Zeta potential of all biopolymers decreased linearly as a function of pH. CH presented higher values, and GeB, the lowest one, being the only having negative values at pH > 5. Overall, the pH influenced the rheological and viscoelastic properties of the colloidal solutions: shear stress and apparent viscosity increased as a function of pH. Other assays were carried out at 3% and 5% strain, for GeA:CH and GeB:CH, respectively. In the sol domain, G’ and G” (1 Hz) increased linearly for GeA:CH. But for GeB:CH, they increased in two linear different regions: one function between pH 3.5 and 5.0 and another one between 5.0 and 6.0, being a more important effect was visible in this last domain probably due to the negative net charge of gelatin, above it pI. An effect in two domains was also visible for Tanδ, explained in the same manner as previously. The GeB:CH blends behaved like diluted solutions, and transition temperatures increased as a function of pH.