High Shear Mixing for Lubricant Homogenization

Mixing liquids with unequal viscosity involves complex flows and a nontrivial diffusive feedback. As an insightful reference case, we study the deformation of a spherical blob with viscosity , sheared in a miscible bath with viscosity . Experiments resolve the transition from unbounded stretching, at low , to rollinglike motion, at large . In between the blob is transiently substretched before destabilizing into swirling structures. Exact solutions of the flow recover all three regimes and predict a transition ratio _{c}3.975. We discuss the dramatic impact of the flow transition on mixing and propose scaling laws for the blob mixing time in the limit of large Pclet numbers, suggesting mixing could be independent of shear rate at large .

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Pulping equipment and system that improves dispersion and mixing of pulp by utilizing a specially designed drive shaft and shell body configuration to generate enhanced shear forces.

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Determining an accurate state of lubrication is of utmost importance for the precise functionality of machine elements and to achieve elongated life and durability. In this work, a homogenized mixed-lubrication model is developed to study the effect of surface topographies on the coefficient of friction. Various measured real surface topographies are integrated in the model using the roughness homogenization method. The shear-thinning behavior of the lubricant is incorporated by employing the Eyring constitutive relation. Several Stribeck curves are generated to analyze the effect of roughness lays and root mean square (RMS) roughness on the coefficient of friction. The homogenized mixed lubrication model is validated against experimental rolling/sliding ball-on-disc results, and a good agreement between simulated and experimental coefficient of friction is found.

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ABSTRACT This study aims to evaluate homogenization techniques and conditions for producing stable, small dropletsize waterinoil (W/O) emulsions intended for incorporation into casein hydrolysateloaded double emulsions. Three commonly used homogenization methods; rotorstator, ultrasonic, and highpressure homogenization were individually optimized utilizing response surface methodology. Instances of overprocessing were observed, particularly with the rotorstator and ultrasonic homogenizers under specific conditions. Nevertheless, optimal conditions were identified for each technique: 530 s at 17,800 rpm agitation speed for the rotorstator homogenizer, 139 s at 39% amplitude for the ultrasonic homogenizer, and 520 s at 1475 bar for the highpressure homogenizer. Subsequently, the W/O emulsions produced under optimal conditions and their respective W 1 /O/W 2 double emulsions were compared. The rotorstator and highpressure homogenized W/O emulsions exhibited comparable narrow dropletsize distributions, as indicated by similar Span values. However, highpressure homogenizatio... Read More

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This chapter provides an overview of the concepts discussed in part 2 of this book. The part provides an introduction to the topics such as mixing and stirrer types, mixing time, power consumption, liquid/liquid dispersions and gas distribution. In the recent past, micromixing has received special attention; this refers to the production of very small eddies with the purpose of mixing the reacting components as fast as possible. Three different types of mixers can be distinguished: mechanical mixers, static mixers, and jet mixers. Stirred vessels are important process items in chemical plants. For heating or cooling, a vessel is often provided with a jacket or a half-pipe jacket. The mixing time 0 is the most important parameter at homogenization. The importance of the mixing time can be investigated on small scale by carrying out experiments at which the mixing time is varied by, for example, variation of the rotational speed of the impeller.

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In this study, a dynamic mixer was designed to mix polymer melts online during extrusion, and the flow of a polymer melt in a mixer was simulated using Polyflow software. The Orthogonal experiment was conducted to analyze the effects of three geometrical parameters (i.e. the length of entrance zone (Li), the gap between the rotor and wall (g), and the diameter of cone-shaped rotor (d2)) on mixing properties of a dynamic mixer. The Li, g, and d2 were optimized for the minimum product of segregation scale (S) and power consumption (P). Finally, the mixing properties of the dynamic mixer were compared with those of SK and SX static mixers. The results indicated that among the above-mentioned three parameters, the g was the most important parameter influencing S, and SP. The minimum SP of 1059 mW was obtained when the Li was 16 mm, the g was 1 mm, and the d2 was 24 mm. The S decreased with the increase of the rotation speed from 120 to 360 r/min, and increased with the increase of the flow rate from 15 to 45 mL/min. However, the P increased with the increase of both the rotation spee... Read More

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Lubricant is vital to improve energy efficiency and workpiece durability for the moving counterpart. High-temperature lubricants are important for the hot rolling process to reduce the rolling force and protect the roller and the strips. The current paper concerns eco-friendly sodium metasilicate as a high-temperature lubricant. A hot rolling mill is employed to evaluate the lubrication effect of sodium metasilicate. The influence of crucial factors of concentration of lubricant and descaling is discussed; the rolled surface was analyzed by scanning electron microscopy, energy dispersive spectroscopy, and 3D profilometer. The results depict that the sodium metasilicate can reduce the rolling force by about 7.8% when the concentration of sodium metasilicate is 18% and above, and descaling of the hot stripe makes the lubrication effect more effective, which can reach a 12.7% reduction in the rolling force. This lubrication is attributed to the formed melts of the sodium silicate layer that offers an easy shearing interface. For the un-descaled samples, the lubricant will be compacted a... Read More

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High-intensity acoustic vibration is a new technology for solving the problem of uniform dispersion of highly viscous materials. In this study, we investigate the mixing characteristics of high-viscosity solidliquid phases under high-intensity acoustic vibration and explore the effect of vibration parameters on the mixing efficiency. A numerical simulation model of solidliquidgas multiphase flow, employing the volume of fluid (VOF) and discrete phase model (DPM), was developed and subsequently validated through experimental verification. The results show that the movement and deformation of the gasliquid surface over the entire field are critical for achieving rapid and uniform mixing of the solidliquid phases under acoustic vibration. Increasing the amplitude or frequency of vibration can intensify the movement and deformation of the free surface of gas and liquid, improve the mixing efficiency, and shorten the mixing time. Under the condition of constant acceleration, the mixing efficiency of materials is higher at low frequency and high amplitude. Further, we define a relatio... Read More

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A method for mixing medium to highly viscous fluids and suspensions using an agitator device driven by a drive shaft. The agitator device features close-clearance stirring blades and counter-stirring blades that work together to efficiently mix thick materials. The device is particularly suited for mixing pastes and other highly viscous substances.

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A solid-liquid mixing and dispersion device that achieves high slurry filling rates and efficient dispersion through a unique design. The device features a cylindrical dispersing wheel and a tangential discharge port, allowing for continuous circulation of liquid and powder while maintaining optimal feed and discharge speeds. The design enables efficient mixing and dispersion of solid-liquid slurries, particularly in applications where high viscosity and uniformity are critical, such as battery manufacturing, food processing, and pharmaceutical production.

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Through laboratory experiments of oil-in-water emulsification, we show that we can construct a high-shear-rate mixer (precession mixer) by using the precession of a cylindrical container without any mixing blades. For high-shear-rate mixing, a container with a larger diameter and its faster spin are preferable so that the wall velocity becomes large enough. Then, emulsification is most efficient when we set the Poincar number Po=p/s, which is the ratio of the spin and precession rotation speeds, about 0.20.3. When Po is smaller than these values, shear rates in the mixer get much lower, though mixing in the bulk of the container is enhanced. On the other hand, when Po is larger, shear rates near the cylindrical wall get higher but mixing in the bulk drastically declines. Through our systematic parameter survey for efficient emulsification by the precession mixer, we have also discovered an experimental law describing the maximum shear rate in the mixer. Since we can use it to appropriately choose the driving conditions of the mixer according to the properties of the materials to ... Read More

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Abstract Pertaining to the mixing of the nonNewtonian Carreau fluid under electrokinetic actuation inside a plane microchannel, we propose a new design of micromixer that involves inserting a twopart cylinder bearing zeta potential of the same sign but different magnitude in the upstream and downstream directions. We numerically solve the transport equations to predict the underlying mixing characteristics. We demonstrate that a substantial momentum difference between the microchannel's plane wall and cylinder leads to the development of a vortex in the flow pathway, which in turn, enhances mixing substantially. As shown, for a fluid having a highly shearthinning nature, the vortexassisted convection mixing strength increases with diffusivity of the candidate fluids. Moreover, it is shown that for the higher shearthinning nature of the candidate fluid, an increase in cylinder radius enhances mixing efficiency and flow rate simultaneously, resulting in a quick and efficient mixing condition. Additionally, the fluid rheology significantly alters the kinetics of shearinduced bin... Read More

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Bubble evolution and shear thinning effect are main factors affecting lubrication behavior of bubbly oil. In this study, a thermohydrodynamic lubrication model for the bubbly oil considering the bubble evolution and the shear thinning effect was established based on the multiphase mixtures theory. The influence of bubble evolution and shear thinning effect on the static behavior of bubbly oil lubricated bearing was analyzed, and an experimental study was conducted to verify the model. The result shows that the bubble radius is mainly dependent on the liquid pressure; the bearing static behavior is affected by the bubble evolution through the interface effect; the shear thinning effect of the pure oil can be enhanced with regarding the bubble evolution effect.

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The structure and flow behavior of lubricating greases depend on the base oil and the type and concentration of the dissolved thickener. In this study, the linear viscoelastic properties of greases were characterized by combining oscillatory shear and squeeze flow covering a broad frequency range (0.1105 rad s1). Multiple-particle tracking (MPT) microrheology and scanning electron microscopy (SEM) provided further insight into local viscoelastic properties and sample structure on a submicron-length scale. The type and viscosity of the base oil did not affect the absolute value of the complex viscosity and the filament shape formed by a given thickener. High-frequency shear modulus data, however, indicated that the thickener lithium 12-hydroxystearate formed stiffer networks/filaments in poly--olefins than in mineral oils. As expected, the viscosity increased with increased thickener concentrations, but microscopy and high-frequency rheometry revealed that the thickness, length, and stiffness of the individual filaments did not change. In mineral oil, the 12-hydroxystearate thicken... Read More

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Abstract We implicitly assess the distributive mixing of generalized Newtonian fluids with shear-thinning behavior in a journal bearing flow geometry. For this purpose, we firstly develop a finite element code to calculate the flow field parameters. Our numerical algorithm splits the viscous stress tensor into arbitrary Newtonian stress and a source term, which grows gradually during the iterative solution. Therefore, we get a better converging solution than the Picard method, especially for highly shear-thinning fluids. Secondly, considering two inert fluids in the mixing domain, we employ a Lagrangian-Eulerian approach to predict the shape of the interface between two fluids. The results of our numerical analysis provide us the required information to evaluate three implicit mixing criteria: the concentration variance, the striation thickness, and the mean strain function. Then we conduct a parametric study to investigate the effects of different parameters (geometry and rheology) on the distributive mixing state. In addition, we discuss which mixing criteria provide a better evalu... Read More

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Abstract Type of lubricant used for fluid film bearings is one of the most important factors to consider. Bearing characteristics have to maintain steady throughout a wide range of conditions. However, viscosity, which is one of the primary lubricant properties, highly deviates depending on environmental and operational conditions. Macro-molecular micro-structure of lubricants is strongly correlated to temperature and shear rate, leading to a shear thinning behaviour. This work aims in studying a pad bearing lubricated by a shear thinning oil in hydrodynamic region. Hydrodynamic wedge was modelled for a small fixed pad bearing of 8.5 mm inner radius, 14.5 mm outer radius, 40 angle and 50 m inlet outlet film thickness difference. Variety of cases were studied for several runner rotational velocities and minimum film thickness. Lubricant was modelled as a carreau fluid. Load carrying capacity, power losses, friction coefficient, mass flow rate, temperature and viscosity were evaluated. From the aspect of load carrying capacity, this specific pad bearing is optimally operating for r... Read More

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Under limited lubricant supply condition, the lubrication of a slider bearing can be enhanced by discontinuous oil droplets on the lubrication track induced by poor surface wettability. This experimental finding is contrary to the general perception that strong surface wettability favors lubricating film build up. Theoretical lubrication models with the lubricant supply in the forms of oil droplets (Model ) and uniform oil layer (Model ) are established to clarify the odd experimental observation. Results show that oil supply in the form of droplets can achieve better lubrication performance than the uniform oil layer, which are correlated to the experimental finding. The mechanism is probably due to the early film pressure initiation when oil droplets enter the bearing contact.

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The mixing process is often used not only to homogenize the materials, but also to bring out better functions by mixing different materials. In the mixing process involving chemical reactions, it is also important to quickly remove the by-products of the reaction. In this study, a flow field around a single rotor rotating in a partially filled chamber was numerically simulated using a 3D model to examine the interface renewal characteristics of highly viscous fluids. The fluids examined were glycerin, which is Newtonian fluid, and aqueous solution of carboxymethylcellulose (CMC), which is Non-Newtonian fluid. A three-wing rotor was chosen as the mixing rotor. The evaluation of interface renewal was performed using history particles. Also, the flow states were classified into rotational, shear, and extensional flows using the Flow number to analyze the flow field. The velocity distribution obtained by the simulation was in good agreement with the experimental results under the same geometry and conditions. For distributive mixing and interface renewal, CMC results were superior to gly... Read More

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In order to mix highly viscous fluids with minimal energetic input, a new active in-line mixer has been developed in our previous study (El Omari et al., Phys. Rev. Fluids, 2021 [18]). Based on the principle of mixing by chaotic advection, we present in this paper an experimental characterisation of chaotic mixing of Newtonian fluid flows, at low Reynolds number. First, the flow is characterized using velocity field measurements. Distinct flow topologies are detected in the flow. The trajectories of the fluid particles are computed and show the generation of complex structures in the flow. Residence time distributions reveal that the fluid particles spend more time in the mixer under favorable controlling conditions. Finite size Lyapunov exponents are calculated and indicate that the flow is more chaotic for these conditions. Next, the mixing patterns are visualized and showed that the mixing is more homogeneous under the same favorable conditions for which the fluid particles are sufficiently subjected to the stretching and folding mechanism.

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The mixing process is used not only to homogenize the materials, but also to bring out better functionality by mixing different materials. In the mixing process, temperature control during mixing is important to prevent thermal deterioration of the material and control chemical reactions. In this study, a 3D model was used to numerically simulate the flow field around a single rotating rotor in a partially filled chamber to investigate the thermal flow characteristics of a highly viscous fluid. The liquids examined contained glycerin, a Newtonian fluid, and carboxymethyl cellulose (CMC) aqueous solution, a non-Newtonian fluid. A three-wing rotor was chosen as the mixing rotor and the shear heating of viscous fluid was modeled by heating the tip of the rotor wing with a heater. Obtained simulation results of the temperature distribution around the rotor was agreed well with the independently performed experimental results. Evaluation of thermal flow properties was performed using history particles. Also, in order to analyze the temperature field, the flow rate through the rotor tip wa... Read More

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