Preparing Monodispersed Hydrogel Microspheres and Microcapsules

1998 ◽  
Vol 550 ◽  
Author(s):  
Y. Senuma ◽  
Ch. Lowe ◽  
Y. Zweifel ◽  
J. G. Hilborn ◽  
I. Marison
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Flow Rate ◽  
Large Scale ◽  
Alginate Beads ◽  
Model System ◽  
Drop Formation ◽  
Narrow Size Distribution ◽  
Spinning Disk ◽  
High Degree

AbstractOur spinning disk atomization (SDA) can, relative to other existing techniques, produce micronsized particles of very narrow size distribution. The aim of this work is to present this technology for the production of alginate microspheres. We have atomized and gelled aqueous alginate solutions into very narrowly dispersed microspheres with sizes ranging from 300 to 600 μm. Here the interest is to design particles of a given size with a narrow size distribution and to show a new method of encapsulation using the SDA. The viscosity and flow rate contributions in the drop formation is qualitatively analyzed to show how it affects the droplet size. In addition, a technique for high degree of encapsulation will be presented. As an example, yeast has been used as a model system. The production of yeast loaded microspheres will show the potential of the technique for biotechnology applications. Such alginate beads could potentially serve as carriers for acitive substances or cells in large scale bioreactors.

Large-scale production of spherical Y2O3:Eu3+ phosphor powders with narrow size distribution using a two-step spray drying method

RSC Advances ◽  
2014 ◽  
Vol 4 (108) ◽  
pp. 62965-62970 ◽  
Author(s):  
Jung Sang Cho ◽  
Kyeong Youl Jung ◽  
Mun Young Son ◽  
Yun Chan Kang
Keyword(s):  
Size Distribution ◽  
Spray Drying ◽  
Mass Production ◽  
Large Scale ◽  
Scale Production ◽  
Narrow Size Distribution ◽  
Drying Method ◽  
Large Scale Production

Dense spherical Y2O3:Eu3+ phosphor particles with a narrow size distribution were successfully prepared by using a two-step spray drying method. This method is easily scalable and can therefore be applied to the mass production of phosphor particles with high photoluminescence.

Experimental Study of Droplet Size Distribution Produced by a Multi-Orifice Effervescent Atomizer

2012 ◽  
Vol 166-169 ◽  
pp. 3056-3059 ◽  
Author(s):  
Fang Xu ◽  
Wei Dong ◽  
Liang Qiang
Keyword(s):  
Experimental Study ◽  
Size Distribution ◽  
Droplet Size ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Injection Pressure ◽  
Droplet Size Distribution ◽  
Liquid Injection ◽  
Effervescent Atomizer ◽  
Pressure Water

A new multi-orifice effervescent atomizer used for fire fighting was developed. The droplet size distribution of the spray produced by the nozzle was measured by laser Doppler particle analyzer. And the influence of liquid injection pressure, water flow rate and atomizer internal geometry was studied.

STRUCTURE AND MAGNETIC PROPERTIES OF MANGANESE OXIDE NANOPARTICLES PREPARED BY ARC SUBLIMATION

2010 ◽  
Vol 24 (31) ◽  
pp. 3025-3032 ◽  
Author(s):  
P. Z. SI ◽  
H. X. WANG ◽  
W. JIANG ◽  
J. G. LEE ◽  
C. J. CHOI ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Manganese Oxide ◽  
Size Distribution ◽  
Exchange Bias ◽  
Large Scale ◽  
Oxide Nanoparticles ◽  
Narrow Size Distribution ◽  
Manganese Oxide Nanoparticles

Manganese oxide nanoparticles with narrow size distribution were prepared in large scale by arc sublimation of bulk MnO . Although MnO is antiferromagnetic, the as-prepared manganese oxide nanoparticles exhibit ferromagnetic behaviors with coercivity and exchange bias up to 417,065 A/m and 162,099 A/m at 5 K, respectively. We attribute these anomalous magnetic properties to the presence of ferrimagnetic Mn 3 O 4, uncompensated surface spins and their coupling to the antiferromagnetic MnO .

Influence of Semicontinuous Processing on the Rheology and Droplet Size Distribution of Mayonnaise-like Emulsions

2009 ◽  
Vol 15 (4) ◽  
pp. 367-373 ◽  
Author(s):  
C. Bengoechea ◽  
M.L. López ◽  
F. Cordobés ◽  
A. Guerrero
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Flow Rate ◽  
Droplet Size Distribution ◽  
Egg Yolk ◽  
Continuous Phase ◽  
Agitation Speed ◽  
Viscosity Data ◽  
Pumping System ◽  
Oil In Water

Oil-in-water (o/w) emulsions stabilized by egg yolk, with a composition similar to those found in commercial mayonnaises or salad dressings, were processed in a semicontinuous device. This specially designed emulsification device consists of, basically, a vessel provided with an anchor impeller, where the continuous phase was initially placed; a pumping system that controls the addition of the oily phase; a rotor-stator unit, where the major breaking of the oily droplets takes place, and a recirculation system. The design allowed the introduction of a rotational rheometer to obtain viscosity data along the emulsification process. The most important advantages of this in-line emulsification device, when compared to discontinuous emulsification equipment, are the possibilities of recording viscosity data along the process and the higher values for the storage, G', and loss moduli, G'', of the resulting emulsions. The influence of egg yolk concentration, agitation speed, and flow rate over the rheological properties (G', G'') as well as droplet size distribution were investigated. Higher protein concentration, agitation speed and flow rate generally produce emulsions with higher G' and G'' values.

Characteristics of Mean Droplet Size Produced by Spinning Disk Atomizers

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Mahmoud Ahmed ◽  
M. S. Youssef
Keyword(s):  
Droplet Size ◽  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Sauter Mean Diameter ◽  
Disk Diameter ◽  
Downstream Distance ◽  
Spinning Disk ◽  
Mean Diameter ◽  
The Mean

Characteristics of mean droplet size of spray produced by spinning disk atomizers were experimentally investigated. The phase-doppler particle analyzer (PDPA) was used to measure the droplet size of water spray in the downstream distance along the spray trajectory. Effects of various operating conditions on the mean diameter had been studied. The studied variables were: the rotational speed in the range of 838 to 1677 rad/s (8,000–16,000 rpm), the liquid flow rate in the range of 0.56 to 2.8 × 10−6 m3/s (2–10 L/h), the disk diameter in the range of 0.04 to 0.12 m, and the downstream tangential distance along the spray trajectory of up to 0. 24 m. The Sauter mean diameter (d32) was used to represent the mean of generated spray droplet sizes. The results indicated that the Sauter mean diameter can be correlated with dimensionless groups, such as the Reynolds number, Weber number, flow coefficient, and the ratio of downstream distance to disk diameter. Based on this correlation, it was found that the Sauter mean diameter (d32) increases as the downstream tangential distance, and liquid flow rate increase. Similarly, a decrease of rotational speed and disk diameter results in an increase in the Sauter mean diameter (d32). A comparison between the developed correlation and correlations obtained by other researchers has been presented and discussed in detail.

Internal Flow Effects in Prefilming Airblast Atomizers: Mechanisms of Atomization and Droplet Spectra

1986 ◽  
Vol 108 (3) ◽  
pp. 465-472 ◽  
Author(s):  
T. Sattelmayer ◽  
S. Wittig
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Mass Flow ◽  
High Speed ◽  
Internal Flow ◽  
Droplet Size Distribution ◽  
Drop Formation ◽  
Air Velocity ◽  
Liquid Separation ◽  
Liquid Mass

Fuel atomization with prefilming airblast nozzles has been investigated. The present analysis is directed toward a detailed investigation of the atomization processes and the clarification of the fundamental phenomena. Two-dimensional models were utilized. High-speed films, showing the deterioration of the liquid film close to the atomizing edge, reveal the dynamics of the liquid’s deterioration and show the motion of the film during the drop formation. The liquid separation is shown to be a periodic process with the drop formation caused by momentum transfer. The frequency spectrum of the liquid separation is determined by means of an optical technique. It is seen that the main frequencies depend only on the air velocity. They are always lower than the corresponding wave frequencies. The droplet size measurements obtained by a light scattering technique emphasize the dominant role of the air velocity at the atomizing edge. A decrease in the surface tension provides an improvement in atomization quality. Other parameters such as liquid flow rate, liquid viscosity, gap height, and length of the prefilming surface within the nozzle were found not to affect directly the droplet size distribution produced, if the air velocity in each of the two ducts of the nozzle is kept constant. The pressure drop of the air, however, rises. It is shown that the droplet size distribution can be easily determined, if the arithmetic mean value of the air velocity in both ducts is known, e.g., from a calculation of the internal flow. Due to the high liquid mass flow rates of airblast nozzles, the wavy film is partly atomized within the nozzle before the liquid separates at the atomizing edge. The measurements show that the portion of the liquid mass flow atomized remains relatively small and that the droplet sizes are equivalent to those produced at the atomizing edge.

Droplet Formation Through Centrifugal Pumps for Oil-in-Water Dispersions

SPE Journal ◽  
2012 ◽  
Vol 18 (01) ◽  
pp. 172-178 ◽  
Author(s):  
Rosanel Morales ◽  
Eduardo Pereyra ◽  
Shoubo Wang ◽  
Ovadia Shoham
Keyword(s):  
Size Distribution ◽  
Centrifugal Pump ◽  
Droplet Size ◽  
Flow Rate ◽  
Droplet Size Distribution ◽  
Droplet Formation ◽  
Centrifugal Pumps ◽  
Mixture Flow ◽  
Pump Speed ◽  
Water Cut

Summary Droplet formation in oil/water flow through a centrifugal pump has been studied, experimentally and theoretically, for the first time. Droplet-size distribution at the pump outlet has been measured for water-continuous flow as a function of pump speed, mixture-flow rate, and water cut. The measured droplet-size distribution strongly depends on the pump speed: the higher the pump speed, the smaller the droplet size. Negligible effects of mixture-flow rate, water cut, and inlet droplet-size distribution have been observed. Turbulent breakup has been identified as the main mechanism for droplet formation. A mechanistic model is developed for the prediction of droplet-size distribution in a centrifugal pump, showing a fair agreement with the acquired experimental data.

scholarly journals Millimeter-Size Spherical Polyurea Aerogel Beads with Narrow Size Distribution

Gels ◽  
2018 ◽  
Vol 4 (3) ◽  
pp. 66 ◽  
Author(s):  
Despoina Chriti ◽  
Grigorios Raptopoulos ◽  
Maria Papastergiou ◽  
Patrina Paraskevopoulou
Keyword(s):  
Size Distribution ◽  
Large Scale ◽  
High Surface ◽  
High Surface Area ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Scale Production ◽  
High Porosity ◽  
Narrow Size Distribution ◽  
Angle Spinning

We report the room temperature synthesis of spherical millimeter-size polyurea (PUA) aerogel beads. Wet-gels of said beads were obtained by dripping a propylene carbonate solution of an aliphatic triisocyanate based on isocyanurate nodes into a mixture of ethylenediamine and heavy mineral oil. Drying the resulting wet spherical gels with supercritical fluid (SCF) CO2 afforded spherical aerogel beads with a mean diameter of 2.7 mm, and a narrow size distribution (full width at half maximum: 0.4 mm). Spherical PUA aerogel beads had low density (0.166 ± 0.001 g cm–3), high porosity (87% v/v) and high surface area (197 m2 g–1). IR, 1H magic angle spinning (MAS) and 13C cross-polarization magic angle spinning (CPMAS) NMR showed the characteristic peaks of urea and the isocyanurate ring. Scanning electron microscopy (SEM) showed the presence of a thin, yet porous skin on the surface of the beads with a different (denser) morphology than their interior. The synthetic method shown here is simple, cost-efficient and suitable for large-scale production of PUA aerogel beads.

scholarly journals Long-resident droplets at the stratocumulus top

2016 ◽  
Vol 16 (10) ◽  
pp. 6563-6576 ◽  
Author(s):  
Alberto de Lozar ◽  
Lukas Muessle
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Large Scale ◽  
Turbulence Models ◽  
Longwave Radiation ◽  
Droplet Size Distribution ◽  
Droplet Growth ◽  
Small Scale ◽  
Radiative Cooling ◽  
Stratocumulus Clouds

Abstract. Turbulence models predict low droplet-collision rates in stratocumulus clouds, which should imply a narrow droplet size distribution and little rain. Contrary to this expectation, rain is often observed in stratocumuli. In this paper, we explore the hypothesis that some droplets can grow well above the average because small-scale turbulence allows them to reside at cloud top for a time longer than the convective-eddy time t*. Long-resident droplets can grow larger because condensation due to longwave radiative cooling, and collisions have more time to enhance droplet growth. We investigate the trajectories of 1 billion Lagrangian droplets in direct numerical simulations of a cloudy mixed-layer configuration that is based on observations from the flight 11 from the VERDI campaign. High resolution is employed to represent a well-developed turbulent state at cloud top. Only one-way coupling is considered. We observe that 70 % of the droplets spend less than 0.6t* at cloud top before leaving the cloud, while 15 % of the droplets remain at least 0.9t* at cloud top. In addition, 0.2 % of the droplets spend more than 2.5t* at cloud top and decouple from the large-scale convective eddies that brought them to the top, with the result that they become memoryless. Modeling collisions like a Poisson process leads to the conclusion that most rain droplets originate from those memoryless droplets. Furthermore, most long-resident droplets accumulate at the downdraft regions of the flow, which could be related to the closed-cell stratocumulus pattern. Finally, we see that condensation due to longwave radiative cooling considerably broadens the cloud-top droplet size distribution: 6.5 % of the droplets double their mass due to radiation in their time at cloud top. This simulated droplet size distribution matches the flight measurements, confirming that condensation due to longwave radiation can be an important mechanism for broadening the droplet size distribution in radiatively driven stratocumuli.

scholarly journals Long-resident droplets at the stratocumulus top

2016 ◽  
Author(s):  
Alberto de Lozar ◽  
Lukas Muessle
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Large Scale ◽  
Turbulence Models ◽  
Droplet Size Distribution ◽  
Wave Radiation ◽  
Droplet Growth ◽  
Small Scale ◽  
Radiative Cooling ◽  
Long Wave

Abstract. Turbulence models predict low droplet-collision rates in stratocumulus clouds, which should imply a narrow droplet-size distribution and little rain. Contrary to this expectation, rain is often observed in stratocumulus. In this paper we explore the hypothesis that some droplets can grow well above the average, because small-scale turbulence allows them to reside at cloud top for a time longer than the convective-eddy time t*. Long-resident droplets can grow larger because condensation due to long-wave radiative cooling and collisions have more time to enhance droplet growth. We investigate the trajectories of one billion Lagrangian droplets in direct numerical simulations of a cloudy mixed-layer configuration that is based on observations from the flight 11 from the VERDI campaign. High resolution is employed to represent a well-developed turbulent state at cloud top. Only one-way coupling is considered. We observe that 70% of the droplets spend less than 0.6t* at cloud top before leaving the cloud, while 15% of the droplets remain at least 0.9t* at cloud top. Besides, 0.2% of the droplets spend more than 2.5t* at cloud top and decouple from the large-scale convective eddies that brought them to the top, with the result that they become memoryless. Modeling collisions like a Poisson process leads to the conclusion that most rain droplets originate from those memoryless droplets. Furthermore, most long-resident droplets accumulate at the downdraft regions of the flow, which could be related to the closed-cell stratocumulus pattern. Finally, we see that condensation due to long-wave radiative cooling considerably broadens the cloud-top droplet-size distribution: 6.5% of the droplets double their mass due to radiation in their time at cloud top. This simulated droplet size distribution matches the flight measurements, confirming that condensation due to long-wave radiation can be an important mechanism for broadening the droplet-size-distribution in radiatively-driven stratocumulus.

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