Stirring Parameters Research Articles

Assessment of transport phenomena in catalyst effectiveness for chemical polyolefin recycling

Since the dawn of agitated brewing in the Paleolithic era, effective mixing has enabled efficient reactions. Emerging catalytic chemical polyolefin recycling processes present unique challenges, considering that the polymer melt has a viscosity three orders of magnitude higher than that of honey. The lack of protocols to achieve effective mixing may have resulted in suboptimal catalyst effectiveness. In this study, we have tackled the hydrogenolysis of commercial-grade high-density polyethylene and polypropylene to show how different stirring strategies can create differences of up to 85% and 40% in catalyst effectiveness and selectivity, respectively. The reaction develops near the H2–melt interface, with the extension of the interface and access to catalyst particles the main performance drivers. Leveraging computational fluid dynamics simulations, we have identified a power number of 15,000–40,000 to maximize the catalyst effectiveness factor and optimize stirring parameters. This temperature- and pressure-independent model holds across a viscosity range of 1–1,000 Pa s. Temperature gradients may quickly become relevant for reactor scale-up.

Selection of performance indicators on dielectric strength and viscosity for chlorinated polyvinyl chloride with N-Methyl-2-pyrrolidone: Optimization using central composite design-response surface methodology

N-methyl-2-pyrrolidone is a highly polar aprotic solvent that is frequently utilized across a broad range of applications in industry. The composition of chlorinated polyvinyl chloride is commonly flame-resistant and mechanically strong. In this research, the central composite design technique uses response surface methodology to perform a parametric study. The effect of the input variables wt.% (16%, 20%, 24%), stirring speed (300, 600, 900 r/min), and stirring time (20 min, 30 min, 40 min) on the output responses (dielectric strength kV/mm, and viscosity Pascal) were examined. The output responses were recorded during the experiments according to the experimental design. The factors impacting the response were identified through analysis of variance. According to the predicted vs. actual diagram, the confirmed experiments fit well with the predictions. Based on the response surface, the parameter interaction profile was analyzed. According to the contour plots related to each interaction, the maximum value can be achieved within different stirring parameters. Based on the result of optimization, the optimum values of dielectric strength and viscosity were found in (wt.% of chlorinated polyvinyl chloride—18.101%), (stirring speed—664 r/min), (stirring time—21.860 min). The output response obtained from the response surface methodology is the dielectric strength (18.5 kV/mm) and viscosity (37.67 Pa).

Prediction of nano metal matrix composites based on hybrid approach

AbstractThis manuscript proposes a hybrid method to predict the optimal nano‐metal matrix composites. The proposed hybrid technique is the wrapper of the Fire‐Hawk Optimizer (FHO) and Spiking Neural Network (SNN). Commonly it is known as FHO‐SNN method. The main objective of the proposed method is to improve the method parameters for better enhancement in mechanical properties. FHO approach is used to improve the process parameters of stirring squeeze casting method. The SNN predicts optimal parameters. Moreover, the problem based on the casting is reduced. By then the proposed hybrid technique performance is performed in the MATLAB platform and associated with various existing approaches. The proposed system shows the high tensile strength, impact energy and hardness compared with other existing methods.

Measurement and calculation of magnetic flux density generated by the second cooling zone electromagnetic stirring (S-EMS) of a slab continuous casting strand

In the current study, a measurement of the magnetic flux density in the second cooling zone was performed for a 1250 mm width and 200 mm thickness slab continuous casting strand generated by the electromagnetic stirring with varied current intensity and frequency. From the narrow face to the width center of the slab, the magnetic flux density showed a increased, decreased, increased to a peak, and finally decreased trend. The magnetic flux density was decreased from the wide side to the thickness center of the slab, while an increase occurred from the model top to the stirrer center along the casting direction. To broaden the measurement range of the electromagnetic stirring parameters, the electromagnetic field in the strand and stirrer was calculated based on the finite element method, and the current input was achieved using the node loading approach. The effect of the mesh density on the calculation accuracy was investigated, and it was found that the 20 mm cell size in the strand region and the 10 mm cell size in the coil conductor and the iron core were enough to achieve a good agreement between the calculation and measurement. The empirical equations, Bx = 0.165.f 0.63.I −0.57.(–6870.x4–9700.x3–4260.x2–495.x + 90), By = 0.167.f −0.5.I 0.45. (4272.y2 + 0.2733.y + 101.4), and Bz = 0.1724.f −0.5.I 0.45.(0.0191.exp(24.16.z − 16.12.z2) + 2.3) were derived to estimate the local magnetic flux density based on measured values across the width of the slab and calculated values along the casting direction under diverse operational conditions. These equations hold practical significance in elucidating the spatial distribution of magnetic flux density within the strand region in the second cooling zone.

Electrochemical corrosion characteristics of friction stir-reacted aluminum matrix hybrid nanocomposites

This research work involves the advanced microstructural characterization and corrosion resistance of hybrid nanocomposites produced by friction stir-induced reaction in an Al–Mg alloy/TiO2 system tested by potentiodynamic and spectroscopy analyses in the form of polarization and impedance. The impact of TiO2 content and submerged cooling medium were assessed on the subsequent electrochemical behavior of the composites. The electrochemical polarization measurements reveal a substantial variation in the corrosion performance correlated to the chemistry of nanocomposites and aluminum matrix grain structure, depending on friction stirring parameters. The heterogeneity of reinforcing nanoparticles at high fractions can increase the corrosion rate in the stirred region by more than 140 times compared to the primary alloy. This is attributed to secondary phase interfaces and nanoparticle clustering at the grain boundaries, promoting galvanic and pitting corrosion phenomena. In contrast, submerged reactive methods employing a cooling medium led to the formation of ultra-fine/nano-sized cellular structured in-situ hybrid nanocomposites with superior corrosion resistance and an excellent combination of mechanical and chemical properties.

Optimization of Arabinogalactan Sulfation in Process Scaling

To ensure the safety of the arabinogalactan sulfation process, the thermal effect of the reaction (148.26 kJ) was determined by the thermal flux balance method. The dependence of the dynamic viscosity of the reaction medium on the way of introducing the sulfating agent and on its particle size was studied by phase rheology. The stirring process was calculated to substantiate the optimum stirrer design and determine the quality parameters of stirring of the reaction medium. The data obtained allow optimization of the process for producing Agsular® substance in scaling of the production technology.

Numerical simulation of macrosegregation phenomenon in Cu-6wt%Ag alloy ingots fabricated by electromagnetic stirring

The development and research of high strength and conductivity materials are essential for the advancement of high-field magnets, including pulsed magnets. This study investigates the effect of electromagnetic fields on the solidification casting of binary Cu-6wt%Ag alloy ingots with diameters of 40 and 160 mm. A 3D numerical simulation is performed utilizing the continuum model with conservation of total momentum, mass, energy, and species. The results indicate that applying electromagnetic stirring (EMS) to small cross-section ingots can cause many randomly distributed small regions with higher segregation degrees inside the ingot, which is not conducive to improving the macrosegregation inside the ingot. For large cross-section ingots without EMS, compared to small cross-section ingots, there is more severe macrosegregation inside the ingot, especially the extreme center segregation with a maximum segregation degree of about 414%. EMS can effectively control macrosegregation within a specific range and eliminate center segregation. When the linear EMS's magnetic induction intensity is set to 0.06 T, the maximum segregation degree near the ingot center can be reduced to less than 260%. Simultaneously, the EMS induced forced convection is also instability, leading to numerous haphazard solute accumulations and depletions, which explains many small segregation regions in the ingot. In terms of improving macrosegregation in large cross-section ingots, Linear EMS has a definite advantage over rotary EMS. It is possible to keep the entire segregation degree in the ingot below 100% when the linear EMS's magnetic induction intensity is set to 0.036 T and the stirring frequency is 4 Hz. The ideal stirring parameters range for linear EMS is to maintain the magnetic induction intensity at around 0.036 T and the stirring frequency in the range of 4–8 Hz.

On the Efficient Particle Dispersion and Transfer in the Fabrication of SiC-Particle-Reinforced Aluminum Matrix Composite

Lightweight SiC-particle-reinforced aluminum composites have the potential to replace cast iron in brake discs, especially for electric vehicles. This study investigates the effect of SiC particle size and matrix alloy composition on the resulting transfer efficiency and particle distribution. The performance of a specially designed stirring head was studied using a water model, and the stirring head conditions were assessed to understand the particle transfer and dispersion mechanisms in the molten aluminum. The standard practice of thermal pre-treatment promotes the wetting of the reinforcing particles and commonly causes clustering before the addition to the melt. This early clustering affects the transfer efficiency and particle dispersion, where their interaction with the melt top-surface oxide skin plays an important role. In addition, the transfer efficiency was linked to the particle size and the chemical composition of the matrix alloy. Smaller particles aggravated the degree of clustering, and the addition of rare earth elements as alloying elements in the matrix alloy affected the particle dispersion. The stirring parameters should be selected to ensure cluster disruption when the carbides are added to the melt.

Impact of stirring regime on piezocatalytic dye degradation using BaTiO3 nanoparticles

There is increasing demand to use readily accessible waste energy to drive environmentally friendly processes. Piezocatalysis, the process of converting mechanical energy such as vibration into a chemical process, is a breakthrough next generation approach to meet this challenge. However, these systems currently focus on using ultrasound to drive the chemical reaction and are therefore expensive to operate. We show that by using simple mechanical stirring and BaTiO3 particles we can remove Rhodamine B dye molecules from solution. After evaluating a range of stirring parameters, we demonstrate that there is an interplay between stirring speed, volume of liquid, catalyst structure and rate of dye removal. Our maximum degradation rate was 12.05 mg. g−1 catalyst after 1 h of mechanical stirring at favourable conditions. This development provides a new insight into a low energy physical technique that can be used in environmental remediation processes.

A sampling platform incorporating 3D-printed paddles-stirrers coated with metal-organic framework MIL-100(Fe) for in-situ extraction of phenolic pollutants in biodigester supernatant and wastewater effluent samples

In this work, a portable paddle stirrer platform for solid-phase extraction of chlorophenols, p-nitrophenol, and bisphenol A is presented. These compounds are important environmental pollutants and toxic inhibitors of the anaerobic treatment of wastewater. The platform integrates 3D-printed paddle stirrers coated with the metal-organic framework MIL-100(Fe), which is prepared in 10 min using a green microwave-assisted synthesis. This coated stirrer serves as an adsorbent for the preconcentration of phenols. The device is assembled with an electric motor that agitates the sample in a sample container. The sampler can be used for in-situ extraction of the analytes, eliminating the need for transporting samples to the laboratory. The analytes are eluted through ultrasonic desorption before analysis by HPLC-DAD. An exhaustive study of the stirring and extraction parameters was conducted. Under optimum conditions, the detection limits ranged from 0.3 to 1.7 μg L−1, and the precision, expressed as the relative standard deviation, showed intraday and interday ranges of 1.2–5.1% and 4.5–6.8%, respectively. The accuracy was evaluated using spiked samples of wastewater effluent and biodigester supernatant, and it provided relative recoveries in the range of 91.5–108.5%.

Intensification design of green crystallization separation: Process optimization and technology coupling

This work designs different process intensification trajectories in the layer melt crystallization (LMC) to improve the separation efficiency. Parameters of distribution coefficient, interfacial solute distribution factor, and mass transfer coefficient are proposed to figure out the intrinsic correlations of technical variables and target parameters. The first proposal strategy is the optimization of the operating curve, divided into cooling process regulation and temperature cycling strategy. Both techniques can eliminate the fine crystals, thus favoring the crystal growth and reducing the impurities' adsorption. Next is the incorporation of the stirring intensification technique into the LMC. The problem of burst nucleation is restricted significantly through the suitable design of the stirring parameters. At last, a coupling technique that combines suspension and LMC is designed. The crystal seeds generated from the suspension melt can flow into the tubular crystallizer and act as the sites for crystal growth. This coupling technique exhibits excellent separation efficiency and huge potential in industrial production. The proposals for the further development of the LMC technique are given.

Parametric optimization and experimental verification of multi-fertilizer mixing by air blowing and blade stirring based on discrete element simulations

In proportional variable-rate fertilization, improving the uniformity of multi-fertilizer mixing helps to improve the overall utilization efficiency of fertilizers. In this paper, a multi-fertilizer mixing by air blowing and blade stirring was presented. Using fertilizer granules mixing uniformity as an indicator, the method optimized the structures and working parameters of single-blade group stirring, double-blade group stirring and air blowing & double-blade stirring. EDEM and Fluent software were used for the simulation and the results were verified by experiments. The simulation results showed that the appropriate speed range of single-blade group stirring was 600 ∼ 900 r⋅min−1 and the highest mixing uniformity was achieved with the blade mounting angle α of 20°. The best structure of double-blade group stirring was achieved with an upper blade mounting angle β of 20°, a lower blade mounting angle θ of −20° and a spacing h of 89 mm. For the air blowing & double-blade stirring method, the best results were achieved when the input air velocity va was 8.4 m⋅s−1 and the blade speed of agitator nb was 740 r⋅min−1. The mixing uniformity of nitrogen (N), phosphate (P) and potash (K) fertilizer granules reached 98.41%, 98.12% and 98.31%, respectively. The bench test results showed that the mixing uniformity by air blowing & double-blade stirring was better than that by double-blade group, and the mixing uniformity by double-blade group was better than that by single-bladed group, which were consistent with the simulation results. Meanwhile the differences between experimental values and simulation values were within 2%, which showed that the simulation models were reliable. Results from this study can be used as reference for the design of mixing devices of variable-rate fertilization.

Effect of mechanical stirring on the tubular heating process of crude oil

Research on thermal behaviors under the synergy of mechanical stirring and tubular heating can reveal the effect mechanism of mechanical stirring, and determine the optimal stirring parameters. In this paper, the physical and mathematical models of heat transfer in crude oil storage tank under the synergy of tubular heating and mechanical stirring are established, the sliding grid technique is used to model the stirring impeller, which are further numerical calculated by the FVM. Our outcomes demonstrate that through the enhancement of convection, mechanical stirring significantly changes the thermal behaviors and enhances the heat exchange. Precisely, for a 1,000 m3 crude oil storage tank, the stirring of 350 rpm can increase the average velocity by 329%, the heating rate by 89%, and rise the average crude oil temperature from 42.311 °C to 42.586 °C during 2 h of heating. However, the higher crude oil temperature will cause a 1,613 W increase in heat loss power. The heating efficiency has also increased by 10%. Furthermore, mechanical stirring can promote a more uniform temperature distribution. Thus, the volume ratio in the low-temperature region decreases by 10% and that in the high-temperature region increases by 26%. The temperature variance decreases from 4.517 °C2 to 0.275 °C2. However, the velocity and temperature fields are almost the same under different stirring rates. With increasing stirring rate from 100 rpm to 700 rpm, the average heating rate can only increase by 0.026 °C/h, and temperature variance decreases from 0.596 °C2 to 0.086 °C2. With increasing stirring rate, the efficiency of the heating tube does not change significantly. The optimal stirring rate is determined as 350 rpm based on the fitting curve of temperature variance stabilization time and the comprehensive effect.

Optimization of the Stirring Parameters of AZ91Mg-Based Stir Casted Hybrid Composites Using Taguchi and ANN

In the current research, the fabricated Mg hybrid composites amalgamate with the vacuum-based squeezed stir casting process having TiC and Al2O3 reinforcement’s in which AZ91Mg-alloy is the base material. The study includes the processing parameters of the vacuum-based squeezed stir casting method (such as stirring time, stirrer depth, and stirring speed) that have been varied and then investigates their influential effect by using the L16 orthogonal Taguchi approach. By considering these parameters, the tribo-mechanical properties are also optimized like porosity, ultimate strength, and rate of wear loss of Mg-hybrid composites. The result reveals a significant association between processing parameters and optimized tribo-mechanical properties. The results signify that the processing parameters are best optimized at processing parameters of 500 rpm of stirring speed, 5 min of stirring time, and 50 mm of stirrer depth and the optimized tribo-mechanical properties are 0.4% porosity, 245 MPa of ultimate strength, and 0.0011 mm3 per min is the loss of wear rate. However, the ANOVA results contribute that the stirrer depth has the most significant processing parameter compared to other optimized parameters. This research also includes an artificially designed networking model which validates the designated set of empirical data. Thus due to their suitability for abrasion wear AZ91-hybrid composite gives a new divergence towards the designing parts of minuscule airplanes used in surveillance applications such as ailerons and wing flaps.

Computational fluid dynamics study on the effect of stirring parameters on solid–liquid suspension in the slurry electrolysis square tank

As a sustainable hydrometallurgical technology, slurry electrolysis (SE) offers certain advantages in the treatment of complex ores and secondary electronic waste. It is therefore of considerable interest to understand the solid–liquid suspension in the stirred tank for overall process control. Here, a computational fluid dynamics (CFD) model based on the Eulerian-Eulerian framework combined with the kinetic theory of granular flow was employed to investigate the effects of varying the impeller speed (70–150 rpm), solids volume fraction (8–21 %), and particle specific gravity (2–6.7) on solid–liquid suspension behavior in a square tank equipped with electrodes and impeller. The results show that as the impeller rotating speed increases, turbulent kinetic energy is gradually transferred from the lower part of the electrodes to the region near the impeller shaft and between the membrane bags. The solids volume fraction was found to have little effect on the final liquid flow fields, but significantly increased the power consumption. The homogeneity and power consumption were quantified as functions of specific gravity, allowing the degree of homogeneity to be predicted under different operating conditions.

Intensified convective energy tapping in modified tubes using Azadirachta indica brewed zinc oxide as potential thermo-fluids

Reusing certain types of decomposed tree leaves is beneficial for biosynthesizing nanoparticles for nanofluids to meet energy sustainability and conservation. Encapsulating and reductant agents in Azadirachta indica (neem) help with fluid stability besides providing higher thermal transport properties. Sol-gel technique was adopted to prepare zinc oxide (ZnO) nanoparticles with neem solution to obtain neem-doped zinc oxide (ZnOneem) particles. According to the Debye-Scherrer relation, the size of ZnOneem was 36 nm. Optimal fluid stirring and sonication parameters were identified to synthesize and stabilize 0.05, 0.2, and 0.6% concentrated nanofluids with aqua-antifreeze (50:50) without surfactant. While the optimal stirring speed and time of 0.05, 0.2, and 0.6% nanofluids were 322 rpm and 36 min, 329 rpm and 33 min, and 334 rpm and 29 min, respectively, the optimal sonication time were 39 min, 34 min, and 32 min, respectively. However, sodium dodecyl sulphate (SDS) at a dispersion fraction of 0.6 ensured 35 months of good suspension. Pumping these turbulent fluids (Re = 5000–10000) through a microfin tube snug-fit with twisted tape inserts (twist pitch, y = 63, 84, and 105 mm) ensured the best outcomes with all the fluid samples. The Nusselt number ratio of 2.114 is the best at a penalty of 2.228 friction factor ratio with 0.6% concentrated nanofluid at Re = 10,000 circulating within the tube fit with Y = 6 tape. For this case, the Bejan number was 0.72, with the maximum Performance Evaluation Factor (PEF) and the Entropy Performance Evaluation Factor (EPEF) being 1.619 and 154.02, respectively.

Effect of precipitation hardening treatment on hardness and tensile behaviour of stir cast LM4 hybrid composites through TEM and fractography analysis

LM4 hybrid composites reinforced with TiB2 and Si3N4 are fabricated using a two-stage stir casting method and are subjected to precipitation hardening treatment. The efficacy of TiB2, Si3N4, and precipitation hardening treatment on LM4 was investigated. When compared to as-cast LM4, all hybrid composites had displayed better hardness and UTS values. This increase in mechanical properties of hybrid composites may be attributed to the presence of hard reinforcement particles, appropriate stirring parameters, which resulted in uniform reinforcement distribution free of porosity and agglomeration. It was observed that in as-cast condition hybrid composites with a higher wt.% of TiB2 had displayed improved hardness (12.5% higher) and UTS (4.4% higher) values than composites with a higher wt.% of Si3N4, because Si3N4 particles are 3.8 times larger than TiB2 particles. Precipitation hardening treatment enhanced the mechanical properties of hybrid composites, with multistage solutionizing (MSHT) and artificial aging at 100 °C producing the best results. Peak aged (MSHT + aging at 100 °C) hybrid composites exhibited 160, 178, and 202% improvement in hardness and 46, 34, and 30% improvement in UTS when compared to as-cast LM4. This increase in age hardened specimens properties is due to the formation of metastable phases, which were validated using XRD and TEM. Fracture analysis of these as-cast and peak aged hybrid composites revealed a mixed mode of fracture-mostly brittle type, because of the presence of reinforcements, intermetallic phases, and strong interface bonding between matrix and reinforcements.

Optimization of stirrer parameters by Taguchi method for a better ceramic particle stirring performance in the production of Aluminum Alloy Matrix Composite

Aluminum alloy ceramic matrix composites have become widely used in a variety of sectors and will grow in the future with the growth of measures to reduce environmental pollution and the necessity to reduce the use of fossil fuels. Stir casting is the most cost-effective method for mass-producing Aluminum Alloy Matrix Composite; however, it still has certain challenges that need to optimize for its performance. The current gap is to anticipate, recognize, and strive to minimize casting flaws during the liquid phase. Taguchi method for the design of the experiment was used to optimize the stirrer parameters. The signal-to-noise (S/N) ratio (larger is better), hardness, and ultimate tensile strength were employed as response output variables. In this work, it was confirmed that the mechanical properties of aluminum alloys can be enhanced better if the method of adding SiC and SiO2 particles as ceramic reinforcements is improved. The contribution of three parameters in enhancing mechanical properties has been identified. The research proved that there is a significant relationship between the Stirrer Design and the mechanical properties. The optimal stirrer design (D5) for mixing ceramic reinforcements with melted aluminum alloy has been chosen from different designs. Mechanical properties under the effect of the most important stirring parameters have been explained. Finally, adding silicon carbide instead of silica sand enhances the mechanical properties even further.

Influence of Stirring Parameters on Creaminess of Spring Blossom Honey Measured by Crystal Size, Whiteness Index and Mouthfeel

Spring blossom honey from regions with many rape fields tends to crystalize rapidly after harvesting. The crystallization process needs to be controlled by stirring in order to avoid the formation of coarse crystals and to ensure the creaminess of honey. The aim of this study was to investigate how various parameters of the stirring process influence the creaminess of spring blossom honey in order to give recommendations for beekeeping practices. The creaminess was quantified by measuring the crystal size by microscopic analysis, measuring the whiteness index by color analysis using CIE Lab and by sensory analysis. We investigated the influence of five stirring parameters, including the type of stirring device, honey pretreatment, stirring temperature (14 °C to room temperature), stirring interval (1 to 24 times) and stirring time (1-15 min) on the creaminess of honey. We found that the stirring temperature is the most important factor for honey creaminess. At the optimal temperature of 14 °C, other factors like seed honey, stirring time and stirring interval have only a neglectable effect. If the optimal temperature of 14 °C cannot be maintained, as it may happen in beekeepers' practice, sieving the honey with a mesh size of 200 µm before stirring, the addition of seed honey prepared with a kitchen food processor, and using a stirring screw and stirring several times per day is recommended.

An experimental investigation of the mechanical variables influence on soybean biodiesel production using the response surface methodology

Biodiesel is a fuel derived from renewable sources such as vegetable oils, animal fats, or residual oils. Although it is a potential source of energy, the efficiency of the production of this fuel depends on several factors, including variables associated with the stirring and mixing process of the reactions. The proper choice of these variables can avoid the formation of vortices, favor the flow direction and the homogeneity of the mixture, and, consequently, contribute to a higher yield of biodiesel. In this context, the present work investigated the effect of agitation and mixing on the production of soybean biodiesel from the analysis of parameters: impeller (blade - turbine), stirring speed (150 rpm – 300 rpm), and baffle (with-without). For this, a 2³ factorial experimental design was carried out for the methylic and ethylic routes. In the reactions, the oil: alcohol molar ratio, amount of catalyst, time, and temperature were fixed. Experimental results indicated higher yields for reactions via the methylic route (more than 93%). Through the statistical analysis, it was also verified that the presence of a baffle and the use of a turbine impeller were the variables of greater statistical significance for the methylic and ethylic routes, respectively. These results showed that the variables considered had a significant impact on the yield of the reactions, although the reaction conditions remained constant, which reinforces that only the control of stirring and mixing parameters can promote optimal yields of the reactions, reducing costs with reagents, operating time, or temperature control.