Rapid Mixing Process Research Articles

An Experimental Study of In-Situ Phase Fraction in Jet PumpUsing Electrical Resistance Tomography Technique

We perform the experiments to investigate in-situ phase fraction in ajet pump using the electrical resistance tomography (ERT) technique. Anew jet pump with ERT sensors is designed to measure in-situ phasefraction and flow regime. The study is based on laboratory experimentsthat are carried out on a 50-mm vertical flow rig for various gas andliquid phase superficial velocities. The different flow patterns of gasliquid in the jet pump and vertical pipe are studied using the ERTtechnique. The results suggest that the ERT system can be used tosuccessfully produce images of gas–liquid flow patterns with framesrates of 58 fps and the in-situ phase fraction with frame rates of5 fps can be obtained. The visualizations of a rapid mixing process inthe throat of a jet pump obtained in this work provide a reliable basisfor theoretical study and optimal design of jet pumps.

Effects of velocity gradient and mixing time on particle growth in a rapid mixing tank

Effects of velocity gradient (G value) and mixing time (t) on the coagulation of particles were investigated by monitoring particle counts in a rapid mixing process. Total particle counts after mixing of 30 s at G value of 200 s(-1) were similar to the summation of clay particles and alum precipitates at alum dose of 30 mg L(-1). Although small particles (microflocs less than 5 microm) were formed within the mixing time of 30 s, macroflocs larger than 8 microm did not increase significantly until the mixing time of 60 s. However, macroflocs larger than 8 microm started to increase after mixing of 75 s and they reached the maximum counts at 150 s. On the other hand, macroflocs larger than 8 microm decreased after mixing time of 180 s due in breaks of the macroflocs, which resulted in resuspension of small particles. The rapid mixing conditions for the maximum growth of macroflocs were the G value of 200 s(-1) and the mixing time of 150 s, which confirmed the best performance of turbidity removal in jar tests. Growth and break of particles and flocs in a rapid mixing step would influence significantly on the sequential flocculation and sedimentation processes for turbidity removal.

On large structures and turbulent mixing in confined mixing layers under forcing

New phenomena have been observed experimentally in a novel rapid mixing process, where a confined mixing layer in a pipe is periodically forced, especially under strong forcing. In the confined configuration without forcing, there are two incommensurable peaks in the scalar power spectrum: one corresponds to the well-known Kelvin–Helmholtz instability, but the other is not known, having a narrow-frequency band around a nearly constant frequency that is independent of the mean flow velocity. With strong forcing within the narrow-frequency band, the spreading angle of the mixing layer is not restrained by the well-known saturation phenomenon, but could even achieve a quasi- 180 ° immediately downstream of the trailing edge, exhibiting an extraordinarily fast mixing. The mixing layer not only biases to the low-speed side as the conventional mixing layer does, it could also be symmetric to the splitterplate and even bias to the high-speed side. These phenomena can be observed only when the forcing is within the narrow-frequency band. We also find that the streamwise vortices, which result from interaction between the primary vorticity and the vorticity originating from the streamwise corner flow between the splitterplate and sidewall immediately downstream of the trailing edge of the splitterplate, could play an important role for these new observations. These streamwise vortices are very sensitive to initial periodic forcing at the narrow-frequency band and amplify very fast. The results indicate that the confined mixing layer in a pipe is a very interesting flow. © 2005 American Institute of Chemical Engineers AIChE J, 2006

Folding Kinetics of an α Helical Membrane Protein in Phospholipid Bilayer Vesicles

We report a detailed kinetic study of the folding of an alpha-helical membrane protein in a lipid bilayer environment. SDS denatured bacteriorhodopsin was folded directly into phosphatidylcholine lipid vesicles by stopped-flow mixing. The folding kinetics were monitored with millisecond time resolution by time-resolving changes in protein fluorescence as well as in the absorption of the retinal chromophore. The kinetics were similar to those previously reported for folding bacteriorhodopsin in detergent or lipid micelles, except for the presence of an additional apoprotein intermediate. We suggest this intermediate is a result of the greater internal two-dimensional pressure present in these lipid vesicles as compared to micelles. These results lay the groundwork for future studies aimed at understanding the mechanistic origin of the effect of lipid bilayer properties on protein folding. Furthermore, the use of biologically relevant phosphatidylcholine lipids, together with a straightforward rapid mixing process to initiate the folding reaction, means the method is generally applicable, and thus paves the way for an improved understanding of the in vitro folding of transmembrane alpha-helical proteins.

Practical design of flocculator for new polymeric inorganic coagulant - PSI

Physical characteristics of flocs formed by new polymeric inorganic coagulant, polysilicato-iron coagulant (PSI) were investigated using kaolinite clay suspended water as test water. Floc density was determined by measuring floc settling velocity and spherical equivalent floc diameter. The floc density function proposed by Tambo and Watanabe could be applied to PSI. Flocs formed by PSI showed higher floc density than those formed by alum at the same floc size. Floc size distribution after the rapid mixing as also determined. PSI could produce well-grown flocs at the stirring speed of 300 rpm. Stirring at 300 rpm for 7 minutes, residual turbidity after 15 minute sedimentation became lower than rapid mixing at 120 rpm for 5 minutes followed by slow mixing at 40 rpm for 25 minutes. Flocs formed by PSI was much stronger than those formed by alum. Using the data obtained, the design parameters of flocculator by use of PSI were estimated following Tambo and WatanabeÕs procedure. According to the estimation, it was suggested that rapid mixing process alone can make well-grown flocs and slow mixing process, which is essential for the conventional water purification system using aluminium coagulants, can be eliminated by use of PSI.

A rapid mixing process in continuous operation under periodic forcing

We introduce a simple and powerful new process for mixing two fluid streams introduced into a pipe via a splitter plate. We demonstrate that the fluids can be thoroughly mixed (at least on large scale) within one pipe diameter downstream of the splitter. Mixing is controlled via periodic velocity forcing of one of the input streams, and is due to amplification of the perturbation as described by instability and receptivity theory. The effectiveness of the mixing depends strongly and non-trivially on the perturbation frequency and amplitude, which distinguishes this method from simple mechanical stirring. The method is effective even at relatively low Reynolds numbers, where laminar flow is observed in the absence of the forcing. Fast mixing can be obtained for different initial velocity ratios of the two inlet streams, rendering the mixing process relatively versatile. Here the mixing method is demonstrated, and potential issues for industrial application are discussed.

Synthesis of Cu-Containing Layered Double Hydroxides with a Narrow Crystallite-Size Distribution

AbstractHydrotalcite-like layered double hydroxides (LDHs) containing different ratios of Ni2+, Cu2+, Mg2+ and Al3+ in the layers have been prepared by a new method, the key features of which are a very rapid mixing and nucleation process in a colloid mill followed by a separate ageing process. The compositions and structural parameters of the materials synthesized using the two routes are very similar, although the degree of crystallinity is slightly higher for the LDHs produced using the new method. The major advantage of the new method is that it produces smaller crystallites, having a very narrow range of distribution of crystallite size. In the conventional coprecipitation process at constant pH, the mixing process takes a considerable time during which nuclei formed at the beginning of the process have a much longer time to undergo crystal growth than those formed at the end of the process. The consequence is that a wide dispersion of crystallite sizes is obtained. In the colloid mill process, however, the mixing and nucleation is complete in a very short time and is followed by a separate ageing process.

Preparation of Layered Double-Hydroxide Nanomaterials with a Uniform Crystallite Size Using a New Method Involving Separate Nucleation and Aging Steps

In particle formation, the method can be just as important as the chemical reaction involved. A new method of synthesizing hydrotalcite-like layered double hydroxides (LDHs) of the type [Mg1-xAlx(OH)2]x+(CO32-)x/2·yH2O (x = 1.7−3.3) is reported. The key features of this method are a very rapid mixing and nucleation process in a colloid mill followed by a separate aging process. The properties of the resulting LDHs are compared with those of materials produced using the conventional coprecipitation process at constant pH. The compositions and structural parameters of the materials synthesized using the two routes are very similar, although the crystallinity is slightly higher for the LDHs produced using the new method. The thermal behavior of the materials synthesized using the two routes is also similar. The major advantage of the new method is that it affords smaller crystallites with a higher aspect ratio, having a very narrow distribution of crystallite size. In the conventional coprecipitation process at constant pH, the mixing process takes considerable time such that nuclei formed at the beginning of the process have a much longer time to undergo crystal growth than those formed at the end of the process. The consequence is that a wide dispersion of crystallite sizes is obtained. In the colloid mill process, however, the mixing and nucleation are complete in a very short time and are followed by a separate aging process. Furthermore, we suggest that the extreme forces to which the nucleation mixture is subjected in the colloid mill prevent aggregation of the nuclei and result in the nuclei having a uniform small size. When the resulting mixture is aged in a separate process, well-formed crystallites with a similarly narrow range of diameters result.

Mechanism of pore formation and structural characterization for mesoporous Mg-Al composite oxides

Mg-Al layered double hydroxides (LDH) with different particle sizes were prepared using different aging times at high supersaturation by a new method developed in our laboratory. The key features of this method are a very rapid mixing and nucleation process followed by a separate aging process. By calcination of LDH at 500°C, mesoporous Mg-Al composite oxides with an extremely narrow pore size distribution were produced. The crystal structure of the Mg-Al composite oxides was a multiphasic one consisting of MgO-like crystals and a layered material.

LDV Measurement of Confined Parallel Jet Mixing

Laser Doppler Velocimetry (LDV) measurements were taken in a confinement, bounded by two parallel walls, into which issues a row of parallel jets. Two-component measurements were taken of two mean velocity components and three Reynolds stress components. As observed in isolated three-dimensional wall bounded jets, the transverse diffusion of the jets is quite large. The data indicate that this rapid mixing process is due to strong secondary flows, transport of large inlet intensities, and Reynolds stress anisotropy effects.

Optimization of Multiple Jets Mixing With a Confined Crossflow

An experimental investigation of a nonreacting multiple jet mixing with a confined crossflow has been conducted. Flow and geometric conditions were varied in order to examine favorable parameters for mixing. The requirement for a rapid and intense mixing process originates from combustion applications, especially the RQL-combustion concept. Thus, the jets were perpendicularly injected out of one opposed row of circular orifices into a heated crossflow in a rectangular duct. Spacing and hole size were varied within the ranges referring to combustor applications. The results presented are restricted to an in-line orientation of opposed jet axis. Temperature distribution, mixing rate, and standard deviation were determined at discrete downstream locations. Best, i.e., uniform mixing can be observed strongly depending on momentum flux ratio. For all geometries investigated, an optimum momentum flux ratio yields to a homogeneous temperature distribution in the flow field downstream of the injection plane. Overly high ratios deteriorate the mixing process due to the mutual impact of the opposed entraining jets along with a thermal stratification of the flowfield. Correlations are introduced describing the dependency of optimum momentum flux ratio on mixing hole geometry. They allow the optimization of jet-in-crossflow mixing processes in respect to uniform mixing.

Abundances for giant stars in the Draco dwarf galaxy

We have determined the abundances of 14 giant stars with +0.2 > M_v_ > -2.5 (19.6 > V > 16.9) in the Draco dwarf galaxy, using a synthetic spectral analysis of the calcium infrared triplet and the strongest line (5183 A) of the magnesium b triplet. The average abundance of the galaxy is ~- 1.9+/- 0.4 (all quoted uncertainties are 1 σ), with a range from ~- 1.4 to -2.4. As previously noted by Zinn and Kinman et al., the abundances seem to fall into two groups, one with an average [Ca, Mg/H] near - 1.6+/-0.2 and the other -2.3+/-0.2. These results confirm and, in two significant ways, extend other claims for an abundance spread. First our study extends to stars about 1.5 mag fainter than previous spectroscopic studies and is thus less sensitive to uncertainties arising from rapid evolutionary or mixing processes near the peak luminosity of the red giant branch and asymptotic giant branch, or from modeling quite extended atmospheres. Second, our study is one of the few to use model atmosphere techniques to match absorption features. A discussion of the origin of the color range among Draco giants and other problems of understanding dwarf spheroidal galaxy formation and evolution is presented.

Cesium 137 and lead 210 in alpine lake sediments: Measurements and modeling of mixing processes

Simulations of 137Cs distribution in lake sediment cores are presented for slow and rapid mixing processes, for different mixing layers, and for different sampling thicknesses. A parameter characterizing the profile distribution is introduced. Interpretation of the 137Cs profiles of seven alpine lakes is given using those simulations leading to an estimate of the sedimentation rate, the type of mixing and the thickness of the mixing layer. These parameters are compared with those obtained independently from 210Pb profiles in three of the lakes. Agreement is satisfactory. The lakes we studied have similar features. In most cases the lakes have mixing which can be approximated by a rapid diffusion process, sedimentation rate of the order of 0.01 g cm−2 yr−1, and a mixing layer of the order of 2–4 cm.

Chernobyl 134Cs, 137Cs, and 210Pb in high mountain lake sediment: Measurements and modeling of mixing process

We have measured the 134Cs, 137Cs, and 210Pb vertical distributions in a lake sediment core. A value of 0.042 Bq cm−2 has been estimated for the atmospheric 137Cs fallout originating in Chernobyl release on the Alpine area: it represents 15% of the residual 137Cs activity due to nuclear tests. Mixing process and sedimentation rate have been deduced from 134Cs and 210Pb distribution. Distribution of 137Cs has been simulated for slow and rapid mixing processes and for various mixing thicknesses. Comparison with the experimental distribution indicates values of mixing thickness and sedimentation rate in agreement with the previously measured ones.

Isolation of the unliganded adenosine 5'-diphosphate, adenosine 5'-triphosphate carrier-linked binding protein and incorporation into the membranes of liposomes.

The ADP,ATP carrier-linked binding protein of beef heart mitochondria was isolated free of ligands, using the detergent 3-lauramido-N,N-dimethylpropylamine oxide. Unlike the preparation of the carboxyatractylate (CAT)-protein complex described earlier, this protein enables direct binding studies to be made with the inhibitor ligands. The protein was characterized with respect to its polypeptide composition, stability against degradation, and immunological properties; the identity of the binding protein with the previously isolated CAT-protein complex was thereby shown. As a step toward reconstitution studies, the isolated binding protein was incorporated into liposomes by a simple rapid mixing process. The complete insertion into the vesicular membrane was demonstrated by chromatography on Sepharose 6B and by immunoprecipitation reactions.

Beryllium-7 in ocean water.

Concentration of the radio nuclide beryllium-7, produced by cosmic rays, was measured in waters collected from both the Atlantic and Pacific oceans. This short-lived nuclide is well suited as a tracer for interactions at the air-sea interface and for the measurement of rapid mixing processes in the surface layer of the ocean.