• Particle and aerosol research
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• v.12 no.4
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• pp.135-143
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• 2016

Removal of water contents in a gas is needed in industrial field of gas processing related on energy production/conversion, and environmental treatment. Inertial separators are economic devices for separating droplets from the gas stream. For accurate understanding of removal process in a curved vane mist eliminator, a numerical model including turbulent dispersion, evaporation and condensation of water vapor at surface of droplets is required. A two-stage curved vane mist eliminator has been modeled, and fluid flow of mixture of air and water vapor and droplet trajectories were solved simultaneously with taking into account two-way coupling. Removal efficiency of droplets with various inlet condition of relative humidities (RH, 40%, 90%, and 100%) were compared. As RH increased, the effect of evaporation decreased and inertial separation efficiencies of droplets obtained increased especially for droplets of diameter below 10 micrometers.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1891-1896
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• 2004

The present article proposes a new droplet collision model including the stretching separation regime and the formation of satellite droplets. The new model consists of a several equations to calculate the post-collision characteristics of colliding droplets and satellite droplets. These equations are derived from the energy balance of droplets between before and after collision. For binary collision of water droplets, the new model shows good agreement with experimental data for the number of satellite droplets. Nevertheless, it is thought that, in order to guarantee the generality of the new model, the improvements should be performed to consider the effects of the bouncing and the reflexive separation, which is essential process in the collision of hydrocarbon droplets.

• Journal of ILASS-Korea
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• v.28 no.3
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• pp.113-118
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• 2023

This study investigates the evaporation characteristics of paired sessile droplets on a heated substrate. In particular, the evaporation time and contact line behaviors were analyzed based on the droplet-to-droplet distance and substrate temperature. The contact line behavior and volume variations were visualized using the shadowgraph method. It was observed that the contact diameter and contact angle exhibited similar behavior for both single and paired droplets regardless of the droplet-to-droplet distance and substrate temperature. The paired droplets demonstrated a longer evaporation time than the single droplet due to the vapor accumulation between the droplets. Furthermore, the scaled lifetime, defined as the ratio of evaporation time between paired and single droplets, increased as the droplet-to-droplet distance decreased and decreased as the substrate temperature increased, attributed natural convection.

• Journal of the Korean Society of Visualization
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• v.15 no.2
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• pp.41-47
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• 2017

Microring/nanoring structure has high applicability for nano-antenna and biosensor thanks to its superior optical characteristics. Although coiling nanowires manufactured using immiscible emulsion droplets have an advantage in mass production, this process also forms nanowire bundles. In this study, we solved the nanowire bundle problem by size-selective sorting of the emulsion droplets in a pinched flow fractionation microchannel. Utilizing silver nanowires and immiscible emsulsion droplets, we investigated the correlation between the size of ring droplets and bundle droplet. We visualized the sorting process for glass particles and microring-containing emulsion droplets. Droplets were sorted based on their size, and the ratio of bundle droplets in solution decreased. This droplet-sorting strategy has potential to help the printing and coating process for manufacturing of ring structure patterns and developing of functional materials.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.107-113
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• 2007

The burning characteristics of interacting droplets with internal circulation in a convective flow are numerically investigated at various particle arrangement and size difference. In this simulation some conditions are fixed, surround gas temperature is 1250K, pressure is 10 atm and drolet's initial temperature is 300K. The transient combustion of arranged droplets, the fixed droplet distances of 4 radii to 20 radii horizontally, is studied. And the range of size of droplet is 75${\mu}m$ to 100${\mu}m$. The results obtained from the present numerical analysis reveal that the transient flame configuration and retardation of droplet internal motion with the horizontal spacing substantially influence lifetime of interacting droplets. At a Reynolds number 10, lifetime of the three droplets with decreasing horizontal droplet spacing increases monotonically. But when droplet spacing decreases further to 4radii, Lifetime of interacting droplets are increase. So Lifetime of interacting droplets exhibits a strong dependence on the horizontal droplet spacing and size difference. It can be investigated well with these conditions to that of single burning droplet.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.92-103
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• 1999

The fuel spray behavior in the intake port of an electronic control port irijection gasoline engine has a strong influence on engine performance, exhaust emission and fuel consumption. Thus, in this study, fuel spray behavior and flow characteristics of the air assist gasoline spray injected into a suction flow in a simulated rectangular intake port have boon investigated. Macro-behavior of spray characteristics was investigated by means of visualization and the measurements of SMD and velocity were made by PDPA. For analysis the flow field with droplets size, droplets are classified five droplets size groups. As a result, the normal distance of suction flow increasing, the relatively large droplets distribution and SMD increase because small droplets easily follow suction flow. Near impinging wail, after impinging against the wall, secondary atomized small droplets of D < $30{\mu}m$ bound from the wall. And the increasement of suction flow progress to the large droplets of D > $100{\mu}m$ distribution. Therefore, SMD are apparently increased near impinging wall, Z/d = 9.0.

• Journal of the Korean Society of Visualization
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• v.12 no.2
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• pp.13-17
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• 2014

In the present study, the optofluidic droplet manipulation in a microfluidic platform was demonstrated via theoretical and experimental approaches. Optical scattering force and gradient force were used to separate and trap droplets. Two types of droplets were generated by a T-junction method in the microfluidic channel. While they approach a test region where the optical beam illuminates the droplets, they were pushed by the optical scattering beam. The displacement by the laser beam is dependent on the refractive index of the droplets. By using the optical gradient force, the droplets can be trapped and coalesced. In order to bring the droplets in a direct contact, the optical gradient force was used to trap the droplets. A theoretical modeling of the coalescence was derived by combining the optical force and drag force on the droplet.

• Journal of ILASS-Korea
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• v.6 no.1
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• pp.18-24
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• 2001

Liquid fossil fuel contaminated by water can cause trouble in the combustion processes and affect the endurance of a combustion system. Using an optical sensor to monitor the water content instantaneously in a fuel pipeline is an effective means of controlling the fuel quality in a combustion system. In two component liquid flows of oil and water, the flow pattern and characteristics of water droplets are changed with various flow conditions. Additionally, the light scattering of the optical sensor measuring the water content is also dependent on the flow patterns and droplet characteristics. Therefore, it is important to investigate the detailed behavior of water droplets in the pipeline of the fuel transportation system. In this study, the flow patterns and characteristics of water droplets in the turbulent pipe flow of two component liquids of gasoline and water were investigated using optical measurements. The dispersion of water droplets in the gasoline flow was visualized, and the size and velocity distributions of water droplets were simultaneously measured by the phase Doppler technique. The Reynolds number of the gasoline pipe flow varied in the range of $4{\times}10^{4}\;to\;1{\times}10^{3}$, and the water content varied in the range of 50 ppm to 300 ppm. The water droplets were spherical and dispersed homogeneously in all variables of this experiment. The velocity of water droplets was not dependent on the droplet size and the mean velocity of droplets was equal to that of the gasoline flow. The mean diameter of water droplets decreased and the number density increased with the Reynolds number of the gasoline flow.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1317-1322
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• 2004

In this report, the heat transfer model of spray cooling on hot surface was developed by focusing on the effect of rebound motion of droplets. In the model, it was assumed that droplets rebound repeatedly on the hot surface and heat transfer upon droplet impact is proportional to sensible heat which heats up the droplets to the saturation temperature. In addition, to take account of the contribution of th heat flux upon impact of rebound droplets, it was assumed that the rebound droplets are distributed following the Gaussian distribution from 0 to L, which distance L is determined by maximum flight distance $L_{max}$. Also the calculated results were compared with existing experimental results.

• Journal of ILASS-Korea
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• v.11 no.2
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• pp.75-80
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• 2006

The present article proposes a new droplet collision model including the stretching separation regime and the formation of satellite droplets. The new model consists of several equations to calculate the post-collision characteristics of colliding droplets and satellite droplets. These equations are derived from the energy balance of droplets between before and after collision. For binary collision of water droplets, the new model shows good agreement with experimental data far the number of satellite droplets.