Motionless Mixers Research Articles

Twin-pipe pumping strategy for stiffening control of 3D printable concrete: From transportation to fabrication

Resolving the contradictions between the pumping and deposition process still remain as a bottleneck in 3D concrete printing. Fluidity retention is beneficial for pumping operations, while fast stiffening after extrusion is indispensable for a high construction rate. To overcome this drawback, an inline mixing strategy, named twin-pipe pumping, using a motionless static mixer and two pumps is proposed. During the printing process, two distinct mixtures are premixed, including a Portland cement-based mixture (without accelerator) and a limestone powder-based mixture (with a high dosage of accelerator). Both mixtures come with a long open time and a high fluidity to optimize the pumping performance. These mixtures are pumped from two separate pipes and merged by the static mixer before extrusion. The stiffening rate of the mixture is then drastically modified inside the static mixer and the combined mixture can reach a high construction rate with good shape stability.

COMPARISON OF DIFFERENT HYDRODYNAMIC CHARACTERISTICS OF AIR- WATER SYSTEM USING DISSIMILAR MOTIONLESS MIXERS

The hydrodynamic characteristics of mixing fluids are always the points to consider in improvement of their mixing quality especially using motionless mixers normally stated as “Static Mixers”. Motionless mixing technique was adopted for Air-Water system with the advantage of negligible power consumption over dynamic mixers. Different hydrodynamic characteristics were experimented using “Baffle Type” static element and were compared to those of already used in recent studies. Dissolved oxygen content, Static mixer geometry (i.e. Baffle, Blade, Wheel, Plate and Needle), mixing fluids flow rates were chosen as variables and selected in this content as rate of mass transfer study which founds out to be significant using “Baffle Type” static element. Volumetric mass transfer was also achieved at higher scale which gives a clear indication of increase the mass transfer coefficient in between the comparison of “Baffle type” element and other mentioned elements. Pressure droplet and depletion in Air bubble size across static elements were visually perceived using Hg-Manometer and still photography respectively. A mathematical model was also developed portraying the Air bubble diameter at different flow rates for this system. Other hydrodynamics like higher Dissolved Oxygen (DO) Content, Less Power consumption were also found to be more advantageous for “Baffle Type” static element.

Development of helical coil based fluidic diode pump for liquid pumping

The main selection criterion for pumps in reprocessing applications is the absence of any moving parts or the moving parts not having any direct contact with the process fluid. There are different types of fluidic pumps such as vortex diode, reverse flow diode, etc. In this work, a new design of helical coil fluidic pump has been developed and demonstrated. Helical coils are widely used in process industries as heat exchangers, reactors, motionless mixers, etc. It is for the first time that the authors are proposing the use of helical coil as a fluidic pump based on its inherent property of high pressure drop as compared to a straight tube.The main objective of this work is to develop an alternate pumping system for reprocessing applications to replace the conventional air lift pump. The helical coil based fluidic diode pump was made up of SS 304 seamless pipe (pipe inner diameter is 9.5 mm) with a 36 mm diameter of helical coil and pitch of 14 mm. In this work, friction factor for the given helical coil was measured from pressure drop experiments. This information was also useful for understanding the transition of the laminar to turbulent region. In order to propose the operating region, the pumping capacity was measured for the helical coil based fluidic pump at different operating conditions. Experimental results show that the proposed hardware is able to pump up to 54 dm3/h. Recommendations have been made for proposing an optimum design.

Development of thermal mixing enhancement method for lower plenum of the High Temperature Test Facility

The High Temperature Gas-cooled Reactor (HTGR) is one of the most mature Gen IV reactor concepts under development today. The High Temperature Test Facility (HTTF) at Oregon State University is a test facility that supports the R&D needs for HTGRs. This study focuses on the issue of helium mixing after the core section in the HTTF, the results of which are generally applicable in HTGRs. In the HTTF, hot helium jets at different temperatures are supposed to uniformly mix in the lower plenum (LP) chamber. However, the level of mixing is not sufficient to reduce the peak helium temperature before the hot jet impinges the LP structure, which can cause issues with structural materials and operational issues in the heat exchanger downstream.The maximum allowable temperature variation in the outlet duct connected to the lower plenum is defined as 40K (±20K from the average temperature), while the CFD simulations of this study indicate that the reference design suffers temperature variations in the duct as high as 100K. To solve this issue, the installation of mixing-enhancing structures within the outlet duct were proposed and analyzed using CFD modeling. We show that using either an optimized “Kwiat” structure (developed in this study) or a motionless mixer installed in the outlet duct, the temperature variations can be brought dramatically, with acceptable increases in pressure drop. The optimal solution appears to be to install double motionless mixers with long blades in the outlet duct, which brings the temperature variation into the acceptable range (from 100K down to 18K), with a resulting pressure drop increase in the HTTF loop of 0.73kPa (6% of total pressure drop).

Experimental set-up of motionless hydraulic mixer and analysis of hydraulic mixing

This contribution presents a mixing process and device which does not contain any moving parts touching the mixing liquid. The process called hydraulic mixing is carried on in a hydraulic mixer which utilizes alternate changes of pressure in a unit caused by adequate in- and out-flows of a gas. The idea of hydraulic mixer (HM) was born during the HAZOP analysis applied at the initial step of the process design. Therefore, the drawn down concept of inherently safer HM was built in laboratory and it led to experimental verification. The performed set of experiments varied in volume of mixed liquid, dimension of device and location of dye injection. The obtained results have shown a feasibility of mixing liquid in the apparatus in which local values of Reynolds number are generally in the laminar regime but if it goes to turbulent (i.e. in the clearance and inner compartment) never reach 11,000. During the carried out experiments various physical phenomena have been observed, such as waving and formation concave–convex structures at liquid interface. Although, hydrodynamic description of the hydraulic mixing with use of modified Reynolds number has been proposed, the description and explanation of obtained results pose difficulties, raised many still open questions and provide challenges for future work.

Hydrodynamics and residence time distribution of liquid flow in tubular reactors equipped with screen-type static mixers

This paper discusses the characteristics of liquid flow through tubular reactors/contactors equipped with woven mesh, screen-type static mixers from hydrodynamic and macromixing perspectives. The effect of changing the screen geometry, number of mixing elements, reactor configuration, and the operating conditions, were investigated by using four different screen types of varying mesh numbers. Pressure drop was measured over a wide range of flow rates (2300⩽Re⩽21,500) and was found to increase with a decreasing mesh opening. Friction factor values are also reported in the work, when compared to other types of motionless mixers, screen-type mixers were found to require much lower energy requirements with very low recorded Z values (1.15⩽Z⩽5) that are two to three orders of magnitude lower than those reported for other motionless mixers.Furthermore, residence time distribution experiments were conducted in the transitional and turbulent regimes (2300⩽Re⩽11,500). Using a deconvolution technique the RTD function was extracted in order to quantify the axial/longitudinal dispersion. The findings highlight that regardless of the number and geometry of the mixer, reactor configuration, and/or operating conditions, axial dispersion coefficients that are lower than those of an empty pipe were always recorded. The wire diameter and mesh opening were found to directly affect the axial dispersion in the reactor, while, the number of elements showed a minor effect. Furthermore, the choice of the characteristic parameter used to calculate the Reynolds number was found to be of paramount importance in analyzing the data.

Residence Time and Concentration Distribution in a Kenics Static Mixer

Static mixers, often referred to as motionless mixers, are in-line mixing devices that consist of mixing elements inserted into a length of pipe. Most of the experimental works in this field have concentrated on establishing design guidelines and pressure drop correlations. Due to experimental difficulties, few articles have been published on the investigation of the flow and mixing mechanisms. In this work, a Kenics KMX static mixer was utilized to study concentration and residence time distribution (RTD) and effect of Reynolds number on mixing. The static mixer had six mixing elements arranged in-line along the length of the tube, and the angle between two neighboring elements was 90°. The length of the mixer was 0.98 m with internal and external diameters of 5.0 cm and 6.0 cm, respectively. The main continuous fluid was water, and NaCl solution was used as a tracer. All experiments were conducted with three replications at three Reynolds numbers, Re = 1188.71, 1584.95, and 1981.19. A dispersion model was used to model the RTD data. The experimental results were compared with the model results and reasonable agreement was achieved.

Intensification of microfiltration using a blade-type turbulence promoter

Intensification of microfiltration has been accomplished using motionless mixers consisting of a series of pairs of semielliptical blades as turbulence promoters. Blade mixers of two aspect ratios 2.5 and 1.3 were tested in the microfiltration of milk (0.1μm membrane). The permeate fluxes are substantially increased by application of blade mixers due to a reduction of both reversible and irreversible fouling. The highest flux improvements of 500–650% for the same cross-flow rate (relative to the conventional operation) were obtained by application of the blade mixer of aspect ratio 1.3.When compared for the same hydraulic dissipated power mixer of aspect ratio 2.5 proved to be slightly more efficient because it causes the lower pressure drop. Despite to the increased pressure drop, the energy savings obtained by application of blade mixers are considerable compared to the conventional operation and to the operation using some other mixers. In the membrane fitted with a blade mixer the flow field changes in a manner which afford the intensive disruption of boundary layer, scouring and removal of fouling forming material. The flow field is characterized by the high cross-flow velocities at membrane wall, alternation of stream line path and swirling motion. Therefore, the application of blade mixers affords an operation under the several times lower initial cross-flow velocity.

Comparison between three static mixers for emulsification in turbulent flow

This paper deals with comparing performances of three different static mixers in terms of pressure drop generated by both single-phase flow and liquid–liquid flow in turbulent flow regime and in terms of emulsification performances. The three motionless mixers compared are the well-known SMX™ and SMV™ and the new version of the SMX called SMXPlus™. This experimental study aims at highlighting the influence of the dispersed phase concentration and some of the geometrical parameters such as number of elements and design of the motionless mixer on droplets size distributions characteristics. Finally, experimental results are correlated in terms of Sauter mean diameter as a function of hydrodynamic dimensionless numbers.

Recent Innovations in Turbulent Mixing with Static Elements

A lot of static mixers are now available, e.g. Sulzer SMV and SMI, Chemineer KM, the Kenics HEV. These products differ quite considerably and the construction have effects on the manufacturing costs and also on the costs for the inbuilt the mixers in a plant. These well known motionless mixers allow to obtain good performances but usually the mixing length necessary for obtaining the homogeneity is longer than 5-10 pipe diameters. Another important constrain is the maximum permissible pressure loss in the operation.

Understanding and Optimizing the SMX Static Mixer

Using the Mapping Method different designs of SMX motionless mixers are analyzed and optimized. The three design parameters that constitute a specific SMX design are: The number of cross-bars over the width of channel, N(x) , the number of parallel cross-bars per element, N(p) , and the angle between opposite cross-bars θ. Optimizing N(x) , somewhat surprisingly reveals that in the standard design with N(p) = 3, N(x) = 6 is the optimum using both energy efficiency as well as compactness as criteria. Increasing N(x) results in under-stretching and decreasing N(x) leads to over-stretching of the interface. Increasing N(p) makes interfacial stretching more effective by co-operating vortices. Comparing realized to optimal stretching, we find the optimum series for all possible SMX(n) designs to obey the universal design rule N(p) = (2/3) N(x) -1, for N(x) = 3, 6, 9, 12, ….

Pressure drop and mixing behaviour of non‐Newtonian fluids in a static mixing unit

AbstractStatic or motionless mixers have received wide application in chemical and allied industries due to their low cost and high efficiency. The pressure drop and mixing behaviour of such mixers have been widely studied. However, the available information for non‐Newtonian fluids is scanty. The results of pressure drop and mixing studies conducted with a locally made motionless mixer (MALAVIYA mixer) and four non‐Newtonian fluids—aq. CMC, PVA, and PEG solutions are reported in this article. The new mixer causes less pressure drop compared to some of the commercial mixers. Mixing behaviour of the unit is more closer to plug flow and a two‐parameter model correlates the dispersion data.

A Review on the Potential Applications of Curved Geometries in Process Industry

The potential industrial applications of curved tubes for single- and two-phase flow are reviewed within the context of physics of flow, trends in the development of technology, and its laboratory to industrial-scale commercialization. Comparison of the performance of curved tube configurations demonstrates its edge over the conventional motionless mixers, heat exchangers, and reactors. Alongside, their respective advantages and limitations are also highlighted. Further, a compendium of the available correlations for single- and two-phase friction factor and heat- and mass-transfer coefficient in curved tubes has also been presented. Key issues regarding the design parameters governing the performance of the curved tubes for mixing and heat- and mass-transfer that impact the research, development, and scale-up or scale-down of such devices are also analyzed. Emerging trends for the development of a new class of curved tubes, namely, inverters and serpentine and chaotic devices are also presented.

Aggregation and Disruption Mechanisms of Nanoparticulate Aggregates. 2. Dispersion of Aggregates Using a Motionless Mixer

A novel motionless mixer named Ramond supermixer (RSM) was used to disperse nanoparticle suspensions under the various process conditions. Commercially available nanoparticles, fumed silica (SiO2) of primary particle diameter (d0) ranging from 7 to 30 nm, zirconia (ZrO2) of d0 = 12 nm, and titanium oxide (TiO2) of d0 = 21 nm, were dispersed either in an ion-exchanged water or in aqueous ethylene glycol solutions. The smaller the d0, the harder it is to disperse the aggregates. Zeta potential was largely dependent on d0 and became independent of process variables and, hence, of aggregate diameter. By evaluation of energy barrier values, the aggregation during disruption was found to be negligible. Aggregate disruption was predominant at the viscous subrange. By balancing mechanical energy with turbulent disruptive energy, a mechanistic model was developed for aggregate disruption. The analysis of fractal dimension showed that nanoaggregates are made up by orthokinetic cluster−cluster collision. Fractal dimensions are invariant throughout the disruption process. The rheological measurements further confirmed the evaluated fractal dimensionality.

Recent Innovations in Turbulent Mixing with Static Elements

Static Mixer consists of a number of stationary mixing elements inserted along the direction of flow in a pipe. Each mixing element allows to divide the flow and to recombine it in a geometric sequence. A lot of static mixers are now available, e.g. Sulzer SMV and SMI, Chemineer KM, the Kenics HEV. These products differ quite considerably and the construction have effects on the manufacturing costs and also on the costs for the inbuilt the mixers in a plant. These well known motionless mixers allow to obtain good performances but usually the mixing length necessary for obtaining the homogeneity is longer than 5-10 pipe diameters. Another important constrain is the maximum permissible pressure loss in the operation. In the recent years, new products composed of a minimum number of elements, have been launched. These new products have a short inbuilt device length, they require a short mixing path and they have low pressure drops. This review analyzes the behaviour of these new innovative static mixers. Keywords: Static mixer, Sulzer CompaX, computational modelling, mixing, turbulent flow

Mixing characteristics of motionless mixers

Motionless mixers have found a large range of applications, including blending, reaction, dispersion, heat transfer and mass transfer. Understanding the mixing processes that occur in these diverse systems is essential for predicting many aspects of practical importance. The objective of this study is to perform the experimental investigations of mixing characteristics for three different motionless mixers. The red color dye tracer was mixed in the main stream of green hair styling gel, and then the mixing efficiency was quantified by calculating the percentage area concentration of red color at the outlet cross section using a digital image processing technique. In the Sulzer SMX and YHC mixer, a single element mixes the fluid nearly in two dimensions, and three-dimensional mixing is accomplished by the next elements aligned at 90° to their former one. In the Sulzer SMX mixer, the flow appears to be globally well mixed after 5 elements, while in the YHC and YNU mixers, it is necessary to globally well mix more than 1 and 2 elements.

Relationship between the Dispersed Droplet Diameter and the Mean Power Input for Emulsification in Three Different Types of Motionless Mixers

Continuous emulsification of low-viscosity liquids was investigated with three different types of motionless mixers, i.e., needle jetting mixer (NJM), Kenics Static Mixer® (KSM) and Ramond Supermixer® (RSM). Kerosene and n-heptane were used as the continuous phase, in which nonionic surfactant (Span80) was dissolved, and deionized water as the dispersed phase. All emulsification runs were carried out at the constant temperature of 303 K. The dispersed droplet diameters in the W/O emulsion were measured by means of microphotography. The size distributions of water droplets in emulsions were normalized by the Sauter mean diameter (d32), and then they obeyed a log–normal distribution function with an upper-limit. The ratio of the maximum droplet diameter (dmax) to d32 was estimated to be 2.30 for NJM and KSM and 1.86 for RSM, respectively. The correlations of d32 with the mean power input per unit mass of the media (PM) were derived. The slopes of the correlation lines on the d32–PM correlation chart took the almost same value of –0.4. This value agreed with the one derived from an isotropic turbulence law in low-viscosity liquids. The line for RSM was located below those for NJM and KSM.

CHARACTERISTICS OF MICROMETER AND SUBMICROMETER SIZE O/W EMULSIONS PRODUCED BY RAMOND SUPERMIXER®

A novel motionless mixer named the Ramond Supermixer® (RSM®) was employed to produce O/W emulsions composed of micrometer and submicrometer-size droplets. Liquid paraffin as dispersed phase, aqueous sucrose solution as continuous phase, and anionic sodium dodecyl sulfate as emulsifying agent were used as the model emulsification system. Pressure drop, droplet size distribution, Sauter mean diameter (d 32), and geometric standard deviation of the droplet size distribution (σg) were investigated under the various combinations of process variables; superficial liquid velocity, number of mixing units, number of passages through RSM®, dispersed phase viscosity (ηd), continuous phase viscosity (ηc), and dispersed phase volume fraction. Different modes of droplet size variations with process variables were obtained, with respect to micrometer- and submicrometer-size ranges, and theoretical explanations are forwarded. For the micrometer-size range, maximum droplet diameter (d max) was proportional to d 32. For the submicrometer-size range, d max varied with d 32 in the range of 1.53–2.19-fold, and a correlation is proposed with K (=ηd/ηc); d 32 and σg were well correlated with the process variables. Furthermore, a semi-empirical mechanistic model was developed for the formation of droplets obtained under inertial sub-range to interpret the effect of process variables.

Formation and Charaterization of Submicrometer Oil-in-Water (O/W) Emulsions, Using High-Energy Emulsification

Submicrometer emulsions were generated by a high-pressure wet-type jet mill and a motionless mixer called the Ramond Supermixer. Kerosene and liquid paraffin were used as the dispersed phase, aqueous sucrose and poly(ethylene glycol) solutions of PEG 400 to PEG 20000 were used as the continuous phase, and sodium dodecyl sulfate was used as a surfactant. The droplet size distribution, the Sauter mean diameter (d32), and the geometric standard deviation of the droplet size distribution (σg) were investigated under various combinations of the operating variables. The analysis of time-scale parameters contributed to an understanding of droplet deformation and possible re-coalescence. The relationship between the maximum droplet diameter and d32 was determined to be a function of the ratio of the viscosity of the dispersed phase to the viscosity of the continuous phase (K). Empirical correlations were constructed for d32 and σg, and a larger similarity was determined to exist within the correlations, irrespect...

CONTINUOUS PRODUCTION OF DISSOLVED OXYGEN-FREE WATER USING RAMOND SUPERMIXER®

ABSTRACT The process of continuous production of dissolved oxygen free water was investigated by means of desorption of dissolved oxygen into fine nitrogen bubbles generated in a novel motionless mixer named Ramond Supermixer® (RSM). The pressure drop across the mixer (ΔPSM) and the volumetric mass transfer coefficient (kL a) during the desorption of oxygen from water were measured for various combinations of process variables; liquid and gas velocities and number of mixing units. The kL a during absorption was smaller by less than approximately 6% than that during desorption. Specific gas-liquid interfacial areas (a) were measured by the chemical absorption method for a CO2-aqueous sodium hydroxide solution system. Such process characteristics as ΔPSM, kL a, and a were correlated with the process variables and compared with those available in the literature. To further confirm the mass transfer characteristics in RSM, the desorption of oxygen from aqueous electrolyte solutions was also investigated. All the correlations obtained for kL a during the desorption of oxygen from water and aqueous electrolyte solutions were compatible to a great higher extent.