Dispersed Drops Research Articles

FORMULASI SHAMPO KRIM CAIR DARI KOMBINASI EKSTRAK DAUN WARU (Hibiscus tiliaceus L.) DAN SARI BUAH JERUK NIPIS (Citrus aurantifolia Swingle.)

Leaves of hibiscus (Hibiscus tiliaceus L.) is widely used by communities to nourish the hair while the juice of lime (Citrus aurantifolia Swingle.) used to eliminate dandruff. Its use is directly less practical than if formulated in the form of shampoo. Cream shampoo formulation development using emulgator sodium lauryl sulfate and sodium hydroxide-coconut oil and the carbopol with concentration 0.1% 0.3% and 0.5%. This study aims to determine the formula that has the most optimal stability. The evaluation was done by testing the stability of organoleptis, homogeneity, determination of pH, type of emulsion, creaming volume, viscosity and size of the dispersed drops before and after accelerated storage. The results show the entire formula is stable because it does not experience phase separation, but the formula that stability is the most optimal use of sodium lauryl sulfate emulgator and karbopol with a concentration of 0.1% because it has a different viscosity and yield value are not significant (α = 0.5). Keywords : Leaf Hibiscus, Lemon, Cream Shampoo, Stability

Protein stabilized oil-in-water emulsions modified by uniformity of size by premix membrane extrusion and their colloidal stability

The pattern of drop size distribution for oil-in-water emulsions stabilized by bovine serum albumin (BSA) and β-lactoglobulin (β-lg) was modified using a membrane extrusion (ME) technique. Initially, premixed emulsions were prepared employing conventional apparatus, a sonicator or rotor–stator type homogenizer, before permeating through a polycarbonate membrane to modify the size and uniformity of oil drops. Due to the shear stress by flow induced by the ME, the coarse oil drops in the premixed emulsions were disrupted resulting in a diminished droplet size and improved uniformity of size. The ME operated at a too high flux, however, led to the coalescence of dispersed particles indicated by the increased diameter and size polydispersity of the oil droplets. Greater ability of β-lg than BSA to be employed for the ME process was reported; this was suggested by the wider flux range providing the required emulsions of β-lg than did BSA. After establishing the adequate permeating flux condition, the stability of the ME emulsions was compared to the control sample without ME. A lower creaming rate as well as better long-term maintaining of the drop size was shown by the ME emulsions compared with the control samples. This actually confirmed the greater colloidal stability of the emulsions containing uniform sized dispersed drops.

The Contribution of Alumina Phase Transformations to the Sintering of Pd Automotive Catalysts

High temperature aging of supported Pd/alumina causes a phase transformation of the transitional (γ, θ or δ) alumina support into alpha (α) alumina. This phase transformation is accompanied by a loss in surface area. This raises the question: how much is the drop in Pd dispersion caused by support sintering? We answer this question by a comparison of chemically similar Pd/alumina catalysts that differ only in one aspect, their physical treatment. The physical treatment is the milling of the support which is often used during wash coating of monolithic automotive catalysts. We show that milling of transitional alumina supports can accelerate their phase transformation into alpha alumina. By comparing catalysts that were milled with those that were not milled, we conclude that the sintering of the catalyst support does not contribute significantly to the sintering of the metal phase. Our results apply specifically to isothermal aging of the catalysts at 900 °C in 10% H2O in N2 for periods of up to 200 h.

Stability and deformation of oil droplets during microfiltration on a slotted pore membrane

The effect of interfacial tension between two fluids, on the passage and rejection of oil droplets through slotted pore membranes is reported. A mathematical model was developed in order to predict conditions for 100% cut-off of oil droplets through the membrane as a function of permeate flux rate. Good agreement of theoretical predictions with experimental data shows that the model can be applied to the filtration of deformable droplets through slotted pore membranes. At high interfacial tension (40mN/m) with lower flux (200lm−2hr−1)droplets of crude oil (27 API) were 100% rejected at droplet diameter 4.3μm using a 4μm slotted pore membrane. At lower interfacial tension (5mN/m), with the same flux rate, 100% rejection occurred at 10μm droplet diameter using the same membrane. It was also found that the droplet rejection efficiency below the 100% cut-off was roughly linear with drop size, down to zero rejection at zero drop diameter. Hence, the model, coupled with this approximate correlation, can be used to predict dispersed oil drop concentration from a known feed drop size distribution.

Transport and Deposition of Evaporating Droplets in a Ventilated Environment

In this study, droplet transport, dispersion, and deposition in a ventilated office with two manikins were studied using a computer-modeling approach. Different airflow distribution systems were used, and an Eulerian approach was employed for the airflow simulation. The trajectories of droplets were evaluated using the Lagrangian approach by solving the equation of droplet motion that included the inertial, viscous drag, Brownian, Saffman lift, and gravity forces. Droplet evaporation was also taken into account by solving the droplet heat and mass transfer equations, thus, allowing for the variation of the droplet size. Mixing and displacement air distribution systems were examined, and trajectories of droplets in the range of 1 to 100 microns emitted by one of the manikins were simulated under a range of conditions. The simulation results showed that the chance for small droplets to leave the room through the exhaust is relatively high. When the mixing air distribution system is used, the drop dispersion is higher than with the displacement distribution system. This in turn suggests that the chance of transmission of air borne diseases is relatively higher for the mixing ventilation system.

Hydrodynamics characteristics of HDS trickle bed test reactor

Abstract Laboratory-scale trickle bed reactors are often used in testing of catalyst life time and activity. One of the important processes is represented by hydrodesulphurization (HDS) of motor fuels and petrochemical fractions. The study of stability of catalysts activity can be influenced both reactions kinetics, hydrodynamics and mass transfer phenomena. In case of ideal behaviour, the liquid could report piston flow. Non-ideal liquid flow can lead to incomplete catalyst particle wetting, which results in poor utilization of the catalytic surface of the particles. It may also expected to occur stagnant zones and imperfect heat transfer and overheating of the catalytic particles. For limitation of this negative phenomena should be diluted catalytic bed by small inert particle provide more contact area. The aim of this study was to determine degree of the effect of hydrodynamic conditions in model trickle bed reactors by residence time distribution method. Objective was to evaluate liquid holdup, axial dispersion and pressure drop of reactor bed consisting of catalyst particles diluted by inert fines to obtain data for process description by PD mathematical model. Hydrodynamic experiments were carried out in model glasses reactor with I.D 30.4 mm. Catalyst –trilobe extrudes of 1.3 mm O.D. was diluted by fine grain SiC 0.1-0.15 mm to obtained complete catalyst wetting and uniform liquid distribution. In presumed range of liquid and gas flow rates, air and water mass flow corresponded to values of hydrogen and hydrocarbons mixture in high-pressure reactor for the study of HDS catalysts. Gas flow was measured by MFC and liquid flow rate was checked by weighing, pressure drop was measured by pressure probe. Along the bed were located three electrodes to measure conductivity signal of responses to impulse of KCl solution. Data acquisition was made by four channel chromatography Clarity SW/HW, with subsequent evaluation by program in Matlab. Simultaneously, the reproducibility of three bed sections of trickle bed catalyst reactor formation of bed diluted by fines was tested by two methods. Effective mean residence time, liquid holdup and axial dispersion were evaluated for each. The range of experimental operation conditions (gas and liquid flow rates) negligible influenced by hydrodynamics was evaluated both experimentally and by hydrodynamics PD model.

Bursting bubble aerosols

AbstractWe depict and analyse the complete evolution of an air bubble formed in a water bulk, from the time it emerges at the liquid surface, up to its fragmentation into dispersed drops. To this end, experiments describing the drainage of the bubble cap film, its puncture and the resulting bursting dynamics determining the aerosol formation are conducted on tapwater bubbles. We discover that the mechanism of marginal pinching at the bubble foot and associated convection motions in the bubble cap, known as marginal regeneration, both drive the bubble cap drainage rate, and are responsible for its puncture. The resulting original film thickness $h$ evolution law in time, supplemented with considerations about the nucleation of holes piercing the film together culminate in a determination of the cap film thickness at bursting ${h}_{b} \propto {R}^{2} / \mathscr{L}$, where $R$ is the bubble cap radius of curvature, and $\mathscr{L}$ a length which we determine. Subsequent to a hole nucleation event, the cap bursting dynamics conditions the resulting spray. The latter depends both on the bubble shape prescribed by $R/ a$, where $a$ is the capillary length based on gravity, and on ${h}_{b} $. The mean drop size $\langle d\rangle \ensuremath{\sim} {R}^{3/ 8} \hspace{0.167em} { h}_{b}^{5/ 8} $, the number of drops generated per bubble $N\ensuremath{\sim} \mathop{ (R/ a)}\nolimits ^{2} \mathop{ (R/ {h}_{b} )}\nolimits ^{7/ 8} $ and the drop size distribution $P(d)$ are derived, comparing well with measurements. Combined with known bubble production rates over the ocean, our findings offer an adjustable parameter-free prediction for the aerosol flux and spray structure caused by bubble bursting in this precise context.

Coalescence behaviors of drop swarms on liquid-liquid interface

The trajectory model of dispersed phase drops and distribution model of drop diameters were derived. By numerical simulation, the analytical results indicate that a large number of dispersed phase drops accumulate on the upper plate in different directions and form a hydrodynamic area with the stream-wise location in the range of 0–0.4 m, where the flow of trickling film obtains kinetic drive from flowing field. The flowing field of trickling film exhibits an unstable state if the stream-wise location is less than 0.02 m, and a stable state otherwise. Moreover, different velocity vectors of drops in the x-y plane result in different interactions between the trickling film and drops. For the non-uniform distribution of drop diameters, there is a stronger interaction between the trickling film and drop if the stream-wise location is less than 0.02 m, because the amplitudes of velocity vectors are higher than those in the range of 0.02–1.0 m. The result reveals a complexity and diversity of stratified two-phase flowing field. On the other hand, both the basic flowing field and distributions of drop diameters have a great influence on the distributions of comparable kinetic energy of drops. The complicated motions of larger drops are helpful to coalescence because they will consume much more kinetic energy on the trickling film than those of smaller drops. The change of comparable kinetic energy of smaller drops is continuous and steady. The smaller drops are easily entrained by the liquid-liquid flowing field.

LOCAL AND AVERAGE STATIC HOLDUPS IN A COUNTERCURRENT FLOW ROTARY DISC CONTACTOR

Local and average static holdups in a rotary disc contactor were studied under various operating conditions. All experiments were performed by use of a swarm of dispersed phase drops and countercurrent continuous phase flow. Different parameters consisting of droplet size, static holdup, and continuous and dispersed phase flow rates were measured experimentally. Based on experimental data, two dimensionless correlations were proposed in the case of immovable rotor discs and also in the case of rotating rotor discs. Finally, two other correlations, in terms of dimensionless numbers, were proposed for predicting average static holdup in the column as a function of average mother drop size, physical properties, rotor speed, phase flow rates, and number of stages in the column for the two mentioned cases. The maximum absolute average relative error and standards deviation of the proposed correlations are 9.8% and 7.3%, respectively.

Experimental and modeling studies on the low-temperature water-gas shift reaction in a dense Pd–Ag packed-bed membrane reactor

In this work, an experimental and modeling study is described, focusing on the performance of a Pd–Ag membrane reactor recently proposed and suitable for the production of ultra-pure hydrogen. A packed-bed membrane reactor (MR) with a “finger-like” membrane configuration has been used for carrying out the water-gas shift reaction (WGS) in the region of low temperature operation using a simulated reformate feed. The experiments were performed under a broad range of operating conditions of temperature (200–300 °C) and space velocity (1200–10,800 L N kg cat −1 h −1); the effect of feed pressure (1–2 bar) was also analyzed, as well as the operating mode at the permeate side: vacuum (30 mbar) or sweep gas (1.0 bar; nitrogen at 1 L N min −1). A one-dimensional, isothermal and steady-state model is proposed, which assumes axially dispersed plug flow pattern and pressure drop in the retentate side and plug flow with constant pressure in the permeate side. An innovative composed kinetic model was also used to describe the catalytic activity of the catalyst for the WGS reaction. In general, the simulation results showed a good agreement to the experimental data, in terms of carbon monoxide conversion and hydrogen recovery (and also outlet retentate composition) using only two fitting parameters related to the decline of H 2 permeability due to the presence of CO. Both simulation and experimental runs showed that the MR achieves high performances, for some operating conditions clearly above the maximum limit for conventional packed bed reactors. The performance reached is particularly relevant when hydrogen is recovered via sweep gas mode (a high sweep flow rate was employed), because a lower partial pressure could be reached than using vacuum pumping. In the first case, almost complete CO conversion and H 2 recovery could be reached.

Numerical simulation of bubble dynamics in a micro‐channel under a nonuniform electric field

A numerical method is used to simulate the motion and coalescence of air bubbles in a micro-channel under a nonuniform electric field. The channel is equipped with arrays of electrodes embedded in its wall and voltages are applied on the electrodes to generate a specified electric field gradient in the longitudinal direction. In the study, the Navier-Stokes equations are solved by using the level set method handling the deformable/moving interfaces between the bubbles and the ambient liquid. Both the polarization Coulomb force and the dielectrophoresis force are considered as the force source of the Navier-Stokes equations by solving the Maxwell's equations. The flow field equations and the electric field equations are coupled and solved by using the finite element method. The electric field characteristics and the dynamic behavior of a bubble are analyzed by studying the distributions of the electric field and the force, the deformation and the moving velocity of the air bubble. The result suggests that the model of dispersed drops suspended in the immiscible dielectric liquid and driven by a nonuniform electric field is an effective method for the transportation and coalescence of micro-drops.

Dispersion of a liquid drop under the effect of an air shock wave with an intensity of 0.2–42 atm

In this paper, we present the results of our experiments on the study of the dispersion of a liquid drop (Ø=2 mm, tributyl phosphate) under the influence of an air shock wave (SW) with an intensity of 0.2–42 atm. The experiments were performed using an air shock tube. The SW was created by exploding a C2H2+2.5O2 mixture, compressed air or compressed helium. Recording of the dispersion process was performed by using high-speed macro- and microfilming (the Schlieren method and traditional filming). Macrofilming allowed us to register an integral picture of the process of drop dispersion and to determine the time of drop evaporation. Microfilming allowed us to resolve fragments of the liquid with sizes ⩾2 μm and to obtain the distribution of the spectrum of drop fragments, which is necessary for calibrating the analytical models.

Characteristic of drop coalescence resting on liquid-liquid interface

The trajectory model of dispersed phase drops and the model of basic flow for drop motion between two inclined parallel plates are derived with the optimized calculation. The analytical results of direct numerical simulation indicate that the basic flow plays an important role in the drop coalescence on liquid-liquid interface. In the stratified two-phase flow field, the smaller droplets are difficult to drain the thin continuous film between the approaching droplets and bulk interfaces and eventually immerse into the trickling film to yield coalescence. They almost attain the velocity of their local surroundings. Moreover, the basic flow exerts a dominant influence on the motion of smaller droplet. The smaller droplets are easily entrained by the basic flow. On the contrary, the larger drop presents advantageous characteristics of coalescence due to its high velocity. The range of 0.3mm < δR ⩽ 0.75 mm is the advantageous drop coalescence condition since the rapidly varied velocity and its first derivative theoretically cause the forces acting on a drop to become imbalanced. On the other hand, the thin layer of the continuous phase drained from the interval between the drops and trickling film should not be neglected in the calculation of shearing force since it is important for drop rotation. The drop rotation is an indispensable factor in coalescence.

Effect of aqueous phase pH on liquid–liquid extraction with impinging-jets contacting technique

The influence of aqueous phase pH on the rate of liquid–liquid extraction was investigated using a two impinging-jets contacting device with a high velocity of jet flows. The recommended chemical system of toluene–acetone–water was employed. Applying pH values from its natural value of 5.6–8, a range in which most industrial waters are lain, for the jets colliding force within 70.3–214.6 mN, leads a reduction in extraction efficiency and overall volumetric mass transfer coefficient up to about 18.9% and 35.2% respectively. A significant high variation is observed when the aqueous phase pH exceeds the water neutral value toward alkali conditions. These variations can be attributed to the adsorption of hydroxyl ions and lowering interfacial tension. A comparison between the results in this work and those for drop dispersion extraction indicates a high sensitivity in the impinging technique. As expected, increasing jets force improves the performance of the contacting device; however, simultaneously, the retarding effect of pH would be intensified. The variation of interfacial tension with pH was obtained and with the aid of dimensionless numbers, an empirical correlation was developed for the prediction of overall volumetric mass transfer coefficient.

Mixing effects on particle formation in supercritical fluids

The process termed solution enhanced dispersion by supercritical fluids (SEDS™) is investigated. In the process particles are created in the rapid antisolvent process using a twin-fluid nozzle to co-introduce the SCF antisolvent and solution. Results of experimental and numerical studies are presented for two regions of pressure: above the mixture critical pressure where a single-phase exists for all solvent–antisolvent compositions, and below the mixture critical pressure where the two-phase region is observed. In experimental studies paracetamol (in the single-phase system) and nicotinic acid (in the two-phase system) were precipitated from ethanol solution using supercritical CO 2 as an antisolvent. To interpret the phenomena affecting creation of the supersaturation and to predict suprsaturation distribution, balances of momentum (flow), species (mixing), energy (heating and cooling) and population (droplet and crystal size distributions) are applied. The Favre averaged k– ɛ model of the CFD code FLUENT is applied together with specific models for precipitation subprocesses and Peng–Robinson equation of state. This includes application of the PDF closure procedure for precipitation and the drop breakage kernel that is based on multifractal theory of turbulence for modelling drop dispersion. Thermodynamic effects of mixing and decompression are included as well. Predicted values not always agree with experimental data but anyhow simulations predict all trends observed in experiments.

Room-temperature deposition of crystalline patterned ZnO films by confined dewetting lithography

In this work patterned ZnO films were prepared at room-temperature by deposition of ∼5 nm size ZnO nanoparticles using confined dewetting lithography, a process which induces their assembly, by drying a drop of ZnO colloidal dispersion between a floating template and the substrate. Crystalline ZnO nanoparticles exhibit a strong visible (525 nm) light emission upon UV excitation ( λ = 350 nm). The resulting films were characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM). The method described herein presents a simple and low cost method to prepare crystalline ZnO films with geometric patterns without additional annealing. Such transparent conducting films are attractive for applications like light emitting diodes (LEDs). As the process is carried out at room temperature, the patterned crystalline ZnO films can even be deposited on flexible substrates.

Size adjustment of spherical temperature-sensitive hydrogel beads by liquid–liquid dispersion using a Kenics static mixer

Temperature-sensitive hydrogel beads were prepared by Kenics static mixer technology. The temperature-sensitive monomer N,N-diethylacrylamide and photo-crosslinkable pre-polymer ENT were used as model hydrogel materials. Drop dispersion of high viscosity polymer material in low viscosity hexadecane was made using the static mixer. Drops of a solution of the mixed materials were rapidly photo-crosslinked by UV irradiation after mixing in the static mixer, and spherical hydrogel beads with narrow, normal size distribution were thus prepared. The Kenics static mixer is a useful device for the preparation of spherical beads of temperature-sensitive hydrogels. The Sauter Mean Diameter of the hydrogel beads swollen in deionized water at 293 K was measured. The experimentally determined dimensionless swollen hydrogel bead diameter was well correlated with the Weber number, degree of swelling and viscosity ratio. The effects of gelation and ENT addition on the bead size were evaluated from the degree of swelling. The correlation equation can be used for size adjustment of temperature-sensitive spherical hydrogel beads.

Properties of erosive discharge in a gas-dispersion flow

Erosive discharge in the flow of a gas-dispersion mixture (air with dispersed microscopic drops of an electrolyte) has been experimentally studied. The products of erosion were obtained by coating the electrodes with a wax (this method was originally used by N. Tesla). Two phenomena were observed behind the discharge gap, i.e., (i) a linear breakdown in the form of a bead lightning (within 0.5–1 m behind the interelectrode gap) and (ii) the appearance of long-lived plasma formations (plasmoids). Cotton-like wax deposits formed on glass slides were examined in optical microscopes at various magnifications. The propagation of long-lived plasmoids in an applied magnetic field was monitored by a high-speed TV camera. Waveforms of a current transferred by the gas-dispersion flow were measured using a conducting screen. Based on these data, a self-consistent physical model is formulated, which describes the generation, evolution, and decay of the long-lived plasmoids.

Strong Metal Support Interactions of Infiltrated Ni with TiO2 in a Porous YSZ Anode Matrix - A Possible Method for Ni-Stabilization

In earlier research, sintering of Ni infiltrated into porous anodes in SOFCs was responsible for loss in performance. The idea of introducing strong metal support interactions (SMSI) has been investigated as a possible method for curbing the sintering of Ni. Titania, when used as a support in catalysts, has been found to show SMSI behavior with metals, dispersed on its surface. Porous anodes, typically used as the SOFC support (anode supported cells), containing titania and Ni have been prepared using impregnation methods and characterized using Chemisorption, Scanning Electron Microscopy (SEM) and XRD studies. SEM results do indicate strong wetting of nickel particles with titania after reduction at 800åC and reduced amount of sintering on prolonged exposures in hydrogen at high temperature. Hydrogen chemisorption studies also revealed a sharp drop in Ni dispersion from 5.3% to less than 1%, due to the presence of titania, at 800oC confirming SMSI effects in Ni-TiO2-YSZ systems.

Dispersed oil–water–gas flow through a horizontal pipe

AbstractAn experimental study of three‐phase dispersed flow in a horizontal pipe has been carried out. The pressure drop over the pipe strongly increases with increasing bubble and drop volume fraction. Because of the presence of drops the transition from dispersed bubble flow to elongated bubble flow occurs at a lower gas volume fraction. The gas bubbles have no significant influence on the phase inversion process. However, phase inversion has a strong effect on the gas bubbles. Just before inversion large bubbles are present and the flow pattern is elongated bubble flow. During the inversion process the bubbles break‐up quickly and as the dispersed drop volume fraction after inversion is much lower than before inversion, a dispersed bubble flow is present after inversion. (When inversion is postponed to high dispersed phase fractions, the volume fraction of the dispersed phase can be as high as 0.9 before inversion and as low as 0.1 after inversion.) © 2009 American Institute of Chemical Engineers AIChE J, 2009