Effect Of Medium Viscosity Research Articles

Design and Performance Prediction of a Vortex Pump Based on CFD for High Concentration Sludge Dredging

Abstract Aiming at solving the problems of clogging and severe wear of the delivery pump in the sludge dredging project, a design method for a vortex pump was summarized. An open impeller and a cross shaped blade was designed with good passing ability, simple structure, and easy maintenance. The volute flow path profile of the vortex pump was designed as a spiral, and the relationship between the width of the vaneless cavity and the diameter of the impeller was established. Based on CFD, the external characteristics of the DRC45-200-VLS vortex pump were simulated and predicted, with a flow rate of 600 m3/h, a head of 20 m, and a water efficiency of 50%. The effects of medium viscosity, solid phase distribution, and gas phase distribution on the flow field of the vortex pump were analyzed. The results showed that the designed vortex pump had good adaptability to transport high concentration sludge and aerated sludge. Combined with a municipal sludge dredging project, a vortex pump transportation scheme for high concentration sludge dredging was formed.

The effect of medium viscosity and particle volume fraction on ultrasound directed self-assembly of spherical microparticles

Ultrasound directed self-assembly (DSA) allows organizing particles dispersed in a fluid medium into user-specified patterns, driven by the acoustic radiation force associated with a standing ultrasound wave. Accurate control of the spatial organization of the particles in the fluid medium requires accounting for medium viscosity and particle volume fraction. However, existing theories consider an inviscid medium or only determine the effect of viscosity on the magnitude of the acoustic radiation force rather than the locations where particles assemble, which is crucial information to use ultrasound DSA as a fabrication method. We experimentally measure the deviation between locations where spherical microparticles assemble during ultrasound DSA as a function of medium viscosity and particle volume fraction. Additionally, we simulate the experiments using coupled-phase theory and the time-averaged acoustic radiation potential, and we derive best-fit equations that predict the deviation between locations where particles assemble during ultrasound DSA when using viscous and inviscid theory. We show that the deviation between locations where particles assemble in viscous and inviscid media first increases and then decreases with increasing particle volume fraction and medium viscosity, which we explain by means of the sound propagation velocity of the mixture. This work has implications for using ultrasound DSA to fabricate, e.g., engineered polymer composite materials that derive their function from accurately organizing a pattern of particles embedded in the polymer matrix.

Effect of Viscosities on the Spray Characteristics of Pressure Swirl Nozzle

The effects of medium viscosity on the spray flow rate, spray Sauter Mean Diameter, droplet velocity and spray cone angle of pressure swirl nozzles are investigated by making use of the particle dynamics analysis system and high-speed photographic system. Based on the axial and radial distribution characteristics of Sauter Mean Diameter and droplet velocity, the water-glycerol mixture is used to simulate medium with a wide range of viscosities. It is found that with the increase of viscosity, the turbulence of the medium flow and the swirling effect is weakened, and the rated pressure becomes larger and the spray flow rate increases. Spray Sauter Mean Diameter and droplet axial velocity becomes larger, while the spray cone angle decreases. The development of the axial velocity distribution of spray cone is characterized by the radial and axial position parameters. The area of the large-droplet region on both sides of spray cone becomes larger, and the area of small-droplet region near the axis becomes smaller.

Viscous Media Slow Down the Decay of the Key Intermediate in Bacterial Bioluminescent Reaction.

The effects of medium viscosity on the decay rate of the 4a-hydroperoxyflavin intermediate of the bioluminescent reaction was investigated. It was found that at low concentrations of glycerol or sucrose (viscosity 1.1-1.3 cP) the decay rate rises, whereas a further increase in viscosity to 6.2 cP leads to a decrease in the decay rate following a power function with an exponent of 0.82-0.84. Using molecular dynamics methods, it was shown that the presence of glycerol and sucrose molecules causes a change in the mobility of the amino acid residues in the active center of luciferase, particularly those responsible for binding of flavin. The results obtained are indicative of two opposite effects of viscous media with glycerol and sucrose: (1) destabilization of 4a-hydroperoxyflavin due to a change in the structural and dynamic properties of the protein and (2) stabilization of this intermediate by the decrease in the diffusion rate of its decay products.

Cellulase-added cassava ethanol process boosts ethanol titer and reduces glycerol production

Cassava is a widely used raw material for bioethanol production. In addition to starch, there is about 4–5 % (w/w) cellulose in cassava tuber, which is not utilized in current cassava ethanol process. Here, a bolt-on cellulase-added ethanol process was developed to realize the in situ conversion of cellulose in cassava tuber. As a result, the final ethanol titer increased from 127.94 g/L to 131.84 g/L, with 57.17 % cellulose and some recalcitrant starch additionally hydrolyzed. Moreover, the titer of glycerol, a main by-product of ethanol fermentation, decreased from 10.78 g/L to 9.95 g/L and the ratio of ethanol/glycerol increased from 11.87 to 13.25. To investigate the reason for the decreased glycerol production in this cellulase-added cassava ethanol process, the effect of medium viscosity on glycerol production was extensively investigated, which indicated, for the first time, that the reduction of glycerol biosynthesis was due to decreased viscosity aroused by the cellulase addition. Overall, this cellulase-added cassava ethanol process not only realized the conversion of cassava cellulose and higher ethanol titer, but also reduced the production of glycerol.

Effect of medium viscosity on rheological characteristics of magnetite-based magnetorheological fluids

This study examined the magnetorheological (MR) behavior of magnetite-based MR fluids according to the magnetite concentration, magnetic field strength, and different viscosity of silicone oil as the carrier fluid. To this end, an experimental design was chosen to decrease the experimental error and provide a better rheological interpretation. The flow behavior parameters increased remarkably with increasing medium viscosity and nanoparticles (NPs) concentration, whereas the magnetic field strength had a milder effect, exhibiting a saturation value above which its effect became almost negligible. Moreover, both the Bingham plastic and power law models were found to fit their flow behaviors well. Almost all the critical rheological parameters of the aforementioned models experienced remarkable improvement after increasing the magnetic field strength, NPs concentration and carried fluid viscosity. In addition, mathematical correlations were derived to model each of the rheological parameters such as plastic viscosity and yield stress (for Bingham fluid model) and the consistency and power-law indices (for power-law model).

Effect of inoculum age and physical parameters on in vitro culture of the entomopathogenic nematode Steinernema feltiae.

Entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae have a symbiotic association with bacteria which makes them virulent against insects. EPNs have been mass produced using in vivo and in vitro methods, including both solid and liquid fermentation. This study assessed the effect of nematode inoculum age on the production of Steinernema feltiae in liquid, solid and biphasic processes. Several physical parameters were also assessed: the effect of medium viscosity, flask size and aeration speed on the recovery and yield of infective juveniles (IJs). Inoculum age treatments included inoculum liquid cultures that were 7, 14, 21 and 28 days old. Nematodes from the same inoculum were added to one liquid medium (liquid culture), one solid medium with bacteria previously grown in sponge (solid culture) and a variation of the solid medium (a biphasic culture), in which the bacteria were first grown in liquid and, then, soaked into the sponges, with the purpose of providing a more homogeneous bacterial culture before nematode inoculation. Experiments were conducted in Erlenmeyer flasks. Eight treatments were established involving combinations of three variables: two media (with and without 0.2% agar), two flask sizes (250 and 150 ml) and two agitation speeds (180 and 280 rpm). The study showed increases in nematode yield for liquid cultures, but not for solid or biphasic cultures, with the advance of the inoculum age up to 28 days of growth. Furthermore, the addition of 0.2% agar to the liquid medium and increasing the aeration rate by using larger flasks with higher agitation speed may increase nematode recovery and final yield. The experiments were conducted using shake flasks but the results may also be applicable for bioreactors.

Effect of Medium Viscosity on the Lift Performance of Full-Metal Single Screw Pump

To deal with the complicated spiral surface of screw pump,this article uses Pro/E to build geometry model.And it improves the method of the grid topology to use the dynamic grid ideas.At the same time,using the method of Computational Fluid Dynamics to numerical simulation for full-metal single screw pump,analysis and study that viscosity affect leakage properties,the torque of surface of rotor and the volumetric efficiency.

Experimental investigation of charged liquid jet efflux from a capillary

The shapes and electrical characteristics of charged liquid (water, ethanol, glycerol, castor oil) jets emitted from a metal capillary have been experimentally studied depending on the applied high voltage. A map of efflux regimes in the flow velocity-applied voltage coordinates is constructed for water. The effects of medium viscosity, surface tension, and charge relaxation time on the laws of jet efflux are analyzed.

Effect of solvent on the free radical polymerization of N,N‐dimethylacrylamide

AbstractThe free radical photopolymerization of N,N‐dimethylacrylamide was investigated at 25 °C and at low conversion in several solvents ranging from weak polar solvents to water. The polymerization is strongly accelerated in the aqueous medium, with the polymerization rate increasing one order of magnitude when the solvent is changed from an organic one to aqueous medium. These results were analysed in terms of macroradical conformation, effect of medium viscosity, aggregate formation, hydrogen bond formation and effect of temperature. The results suggest that the main factor that controls the polymerization rate is a kinetic effect due to the hydrogen bonding between the amide carbonyl group and water molecules. Also, we found that polymer properties, such as the thermodynamic quality of the solvent for the polymer backbone and molecular weight control using transfer agents, are influenced by the intermolecular hydrogen bonding. Copyright © 2010 Society of Chemical Industry

Depletion of high molecular weight dextran from the red cell surface measured by particle electrophoresis

The reversible aggregation of human red blood cells (RBC) by proteins or polymers continues to be of biological and biophysical interest, yet the mechanistic details governing the process are still being explored. A depletion model has been proposed for aggregation by the neutral polyglucose dextran and its applicability at high molecular weights has been recently documented. In the present study the depletion of high molecular weight dextrans on the red cell surface was measured as a function of polymer molecular mass (40 kDa-28 MDa), ionic strength (5 and 15 mM NaCl) and polymer concentration (< or =0.9 g/dL). The experimental data clearly indicate an increasing depletion effect with increasing molecular weight: the effects of medium viscosity on RBC mobility were markedly overestimated by the Helmholtz-Smoluchowski relation, with the difference increasing with dextran molecular mass. These results agree with the concept of polymer depletion near the RBC surface and lend strong support to a "depletion model" mechanism for dextran-mediated RBC aggregation. Our findings provide important new insight into polymer-RBC interactions and suggest the usefulness of this model for fundamental studies of cell-cell affinity and for the development of new agents to stabilize or destabilize specific bio-fluids.

Effect of Medium Viscosity on Breakage Parameters of Quartz in a Laboratory Ball-Mill

The role and effect of liquid medium viscosity on breakage parameters (S and B values) of the batch grinding kinetic model was investigated by grinding a single feed fraction of quartz (20 × 30 mesh) in a batch ball-mill at fixed mill loadings and at 45 vol % solid concentration, using glycerol−water mixtures of different proportions. The primary breakage distributions (B values) were normalized and separated into three different groups for grinding in media viscosities of 0.001(water), 0.002−0.03, and 0.08−0.16 Pa·s, respectively, with higher viscosity range giving proportionally finer products. The disappearance grinding kinetics of the top size showed that the specific breakage rates (S values) depended both on the viscosity of the liquid medium and on the extent of grinding. The specific breakage rates of the top size increased with the fineness of grinding while the breakage of the smaller sizes proceeded approximately in a first-order manner as characterized by a characteristic breakage rate constant. The acceleration of the top-size breakage rates as grinding proceeded was represented by a parameter called the acceleration factor, which correlated reasonably well with the changing slurry effective viscosity. Alternatively, the acceleration factor can be presented in the form of a single generalized first-order plot for grinding at different medium viscosities. The first-order breakage rate constant decreased with increasing medium viscosity over the range from 0.001 to 0.16 Pa·s but not linearly. The proportional variation of net mill power did not match exactly with that of the breakage rate constant on increasing medium viscosity. On the basis of the analysis of grinding results, three grinding regimes were identified relative to the change in medium viscosity but their existence was not confirmed experimentally.

Excited-State Dynamics in the Green Fluorescent Protein Chromophore

The remarkable suppression of radiationless decay by the green fluorescent protein (GFP) is investigated through ultrafast fluorescence spectroscopy of its isolated chromophore in solution. Decay data are measured by fluorescence up-conversion as a function of solvent and wavelength for both neutral and anionic forms of the chromophore. All fluorescence decays are found to be well described by two exponentially decaying components. The effect of medium viscosity is slight, suggesting that the intramolecular motion promoting radiationless decay is a volume-conserving one. A minor effect of solvent polarity and H-bonding ability on the decay times is observed. The two decay constants are independent of emission wavelength, but their relative weights are not. Time-resolved fluorescence spectroscopy shows that the Stokes shift is complete in <100 fs, and that subsequent spectral evolution is limited to a small spectral narrowing. These data are discussed in terms of a two-state two-mode model, originally prop...

Sedimentation and Electrophoretic Mobility Behavior of Human Red Blood Cells in Various Dextran Solutions

To obtain additional information relevant to polymer behavior near human red blood cells (RBC), sedimentation and electrophoretic mobility behavior of RBC in the same suspension were determined for cells in various isotonic solutions of 10.5, 74 and 519 kDa dextran. Regardless of medium viscosity or dextran molecular mass, RBC sedimentation rate could be predicted via the Stokes' equation. Conversely, the effects of medium viscosity on RBC mobility were markedly overestimated by the Helmholtz−Smoluchowski relation, with the error increasing with dextran molecular mass. These results confirm and extend prior electrophoretic mobility studies, agree with the concept of polymer depletion near the RBC surface, and lend strong support to a “depletion model” mechanism for dextran-mediated reversible RBC aggregation.

Effect of medium viscosity in a closed unstirred Belousov–Zhabotinsky system

Complex periodic and aperiodic behaviors are reported in an unstirred Belousov–Zhabotinsky oscillatory reaction containing different concentrations of polyethylene-glycol. A route from chaos following an inverse Ruelle–Takens–Newhouse (RTN) scenario is identified. Thus, hydrodynamic effects, being mainly convective, seem to be responsible for the observed RTN scenario. We demonstrate that the medium viscosity, namely the polyethylene-glycol concentration, is a bifurcation parameter for the sequence chaos → quasi-periodicity → period-1.

Kinetic study on conformational effect in hydrolysis of p-nitroanilides catalyzed by α-chymotrypsin

Effects of medium viscosity on kinetics for the hydrolysis of p-nitroanilides of certain amino acid derivatives catalyzed by α-chymotrypsin have been investigated. Observed data indicate that the overall rate constant, kcat, is hardly affected by the medium viscosity in all the substrates employed and equals the rate constant at the acylation step, k2, in the measured range of viscosity. By comparison with the data on p-nitrophenyl ester substrates reported previously, it is concluded that the formation of the tetrahedral intermediate in the course of the acylation of the enzyme is influenced by conformational change of the enzyme, whereas the breakdown of the intermediate is almost free from conformational effects.

Effect of metal phthalocyanine complex aggregation on the catalytic and photocatalytic oxidation of sulfur containing compounds

Water soluble zinc (II) 2,9,16,23-phthalocyanine tetrasulfonic acid [ZnPc(SO 3H) 4], zinc (II) 2,9,16,23-phthalocyanine tetracarboxylic acid [ZnPc(COOH) 4] and sterically hindered bulky zinc(II) 2,9,16,23-tetrakis(8-quinolineoxy-5-sulfonicacid)-phthalocyanine [ZnPc(QnSO 3H) 4] complexes have been studied as photocatalysts for oxidation of 2-mercaptoethanol and sodium thiosulfate. The ZnPc(QnSO 3H) 4 complex exhibited the highest photocatalytic activity due to its low aggregation degree in aqueous medium. In the presence of tetrabutylammonium chloride, quinoline and ethanol additives the monomerization degree of the ZnPc(SO 3H) 4 and ZnPc(COOH) 4 complexes is increased, their photocatalytic activity being close to that of ZnPc(QnSO 3H) 4. Because of high aggregation degree of ZnPc(SO 3H) 4 and ZnPc(COOH) 4 in viscous medium, the quantum yields of singlet dioxygen generation and the photocatalytic oxidation rates of the sulfur-containing compounds are decreased. The photocatalytic activity of ZnPc(QnSO 3H) 4 is slightly changed in viscous medium and in the presence of additives. The low aggregation degree of this complex allowed to establish enhanced and lowered rates of photocatalytic oxidation of 2-mercaptoethanol and sodium thiosulfate, respectively, on increasing medium viscosity. The effect of medium viscosity on ZnPc(QnSO 3H) 4 photocatalyzed oxidation of the two substrates is discussed.

Effect of viscosity upon hydrodynamically controlled natural aggregates of animal cells grown in stirred vessels.

The effect of medium viscosity upon cell growth and aggregate characteristics of baby hamster kidney (BHK) cells cultivated in stirred tanks was evaluated. Two thickening agents were tested, 9300 MW dextran and a low-viscosity sodium (carboxymethyl)-cellulose; both were used in two different sets of experiments: (i) 250 cm3 Wheaton spinner flasks with a ball impeller operated at 45 rpm; (ii) 500 cm3 Corning spinner flasks with a paddle impeller, operated at constant power dissipation (88 cm2 s-3). Aggregate diameter and the fraction of cells in aggregates increased with the increase in viscosity. Power laws were applied to the experimental results. A dependence of aggregate size upon power dissipation of the order of -0.19 and kinematic viscosity of 0.34 and 0.49 for the constant agitation and constant power dissipation tests were obtained, respectively. A model based upon the entire universal-equilibrium range (i.e., the entire spectrum of isotropic eddies) was used to predict theoretical relationships between the variables studied. The model leads to a power dependence of -0.25 for the energy dissipated in the entire universal-equilibrium range and between 0.25 and 0.5 for the kinematic viscosity in the viscous dissipation subrange, depending on the energy correlation used; it also gives a good explanation for the dependence of aggregate size on the hydrodynamics of the vessel.

The Effect of Substrate Hydrophobicity on the Kinetic Behaviour of ImmobilizedCandida rugosaLipase

Candida rugosa lipase (EC 3.1.1.3.) was immobilized in a hydrophilic polyurethane foam and used in the hydrolysis of olive oil, in H-hexane. The results obtained were compared with those from a previous study, in which the same lipase preparation was used in the esterification of ethanol with butyric acid.The initial rate of hydrolysis increased exponentially with increasing olive oil concentration. In contrast, for the esterification reaction, Michaelis-Menten kinetics with inhibition by both substrates, had been observed.The effect of medium viscosity, stirring conditions and size of immobilization particles could not explain the observed kinetics of the hydrolytic reaction. However, a direct relationship was observed between the log P values of the reaction medium and the initial rate of hydrolysis, i.e., activation of the immobilized Candida rugosa lipase appears to be promoted by a high hydrophobicity of the reaction medium.In the case of the esterification reaction, no similar correlation was found.

Spectral, lifetime and photochemical characteristics of 4-acetoxy-chalcone in viscous media

Both fluorescence and excitation spectra of 4-acetoxy-chalcone (4-AC) are bathochromically shifted as the medium polarity increases. The fluorescence quantum yields are sensitive to medium viscosity and increase sharply as the medium viscosity increases due to prohibition of radiationless deactivation pathways. The fluorescence lifetime of 4-AC in glycerol has been measured as τ = 1.9 ns. The photochemical quantum yields (thought to be a trans-cis photo-isomerization) are also sensitive to medium viscosity with minimum φc values obtained in highly viscous solvents. The effect of medium viscosity on the quenching of 4-AC fluorescence using picric acid as a quencher has been studied. A static-type quenching mechanism is proposed to account for the quenching efficiency as the medium viscosity increases.