• Korean Chemical Engineering Research
• /
• v.56 no.5
• /
• pp.761-766
• /
• 2018

Droplet-based microfluidic device has led to transformational new approaches in various applications including materials synthesis and high-throughput screening. However, efforts are required to enhance the production rate to industrial scale because of low production rate in a single droplet generator. In here, we present a method for enhancing production rate of monodisperse droplets via parallelization of flow-focusing generators. For this, we fabricated a three-dimensional monolithic elastomer device (3D MED) that has the 3D channel structures in a single layer, using a double-sided imprinting method. We demonstrated that the production rate of monodisperse droplet is increased by controlling the flow rate of continuous and dispersed phases in 3D MED with 8 droplet generators. Thus, we anticipate that this microfluidic system will be used in wide area including microparticle synthesis and screening system via encapsulation of various materials and cells in monodisperse droplets.

• Journal of the KSME
• /
• v.23 no.4
• /
• pp.275-279
• /
• 1983

현재 사용중인 내연기관, 가스터어빈, 로켓엔진과 발전소 및 주거용 난방에 이용되는 중 .소형 연소기에서는 고가의 액체연료들을 사용하고 있다. 이 액체연료를 고급동력으로 바꿀 때는 필연 적으로 연소라는 과정을 거치게 되는데 연소과정을 단계적으로 나누어 보면 첫째, 액체연료의 표면적을 크게 하여 연소를 촉진시키기 위한 연료의 미립화(atomization) 과정, 둘째, 미립화된 액적들의 증발 및 기체화한 연료와 공기와의 혼합으로 생성되는 가연성 혼합기 생성과정과 셋째, 가연성 혼합기의 점화, 연소 및 화학반응으로 인한 공해물질의 생성과정들로 대별된다.

• Korean Chemical Engineering Research
• /
• v.50 no.4
• /
• pp.733-737
• /
• 2012

This study reports the microfluidic preparation of monodisperse multiple emulsions using hydrodynamic control. To generate multiple emulsions, we fabricate a microfluidic capillary device based on co-flowing stream without any surface modification of microchannels. Based on the system, we can successfully generate multiple emulsions (W/O/W) using water containing 0.5 wt% Tween 20, n-hexadecane with 5 wt% Span 80, and 10 wt% poly (vinyl alcohol) (PVA) aqueous solution, respectively. Furthermore, we control the number of inner droplets by modulation of flow rate of inner fluid at fixed flow rate of middle and outer fluid. The multiple emulsions having precisely controlled inner droplets' size and number can be applicable for multiple chemical reactions as an isolated microreactor.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.6
• /
• pp.1-7
• /
• 2017

The atomization of a liquid into multiple droplets has many important industrial applications, including the atomization of fuels in combustion processes and coating of surfaces and particles. Ultrasonic atomizing nozzle has a transducer that receives electrical input in the form of a high frequency signal from a power generator and converts that into mechanical energy at the same frequency. Liquid is atomized into a fine mist spray using high frequency sound vibrations. In coating applications, the unpressurized, low-velocity spray reduces the amount of overspray significantly because the droplets tend to settle on the substrate, rather than bouncing off it. The spray can be controlled and shaped precisely by entraining the slow-moving spray in an ancillary air stream using specialized types of spray-shaping equipment. The desired patterns of spray can be obtained using an air stream. To simulate the water mist behavior of an ultrasonic atomizing nozzle using an air stream, the Lagrangian dispersed phase model was employed using the commercial code FLUENT. The effects of the nozzle contraction shape, water droplet size and the pneumatic pressure drop on the spray characteristics were investigated to obtain the optimal condition for coating applications.

• Fire Science and Engineering
• /
• v.30 no.4
• /
• pp.14-19
• /
• 2016

When an interior fire occurs in an apartment building, pollution of the entrance area by fire smoke before an air fan operates makes the evacuation of people very difficult aswhen the fire doors are opened. Numerical simulations using Fire Dynamics Simulator were conducted to determine the impact of a sprinkler on the fire flow velocity. The fire flow velocity was compared depending on the presence of sprinklers and the sprayed droplet size. The configuration and actual dimensions of an apartment building were used in the numerical simulations. The simulation results showed that fire flow velocity becomes smaller when a sprinkler is installed. In addition, the smaller droplet size results in a smaller fire flow velocity because smaller droplets can be evaporated more easily.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.9
• /
• pp.799-804
• /
• 2007

The behavior of spray emanating from an injector to be employed in a liquid-propellant thrust chamber is investigated by optical measurement techniques. The injector has eight holes, each of which has 30 cant angle from the center-axis with the diameter of 0.406 mm. In order to examine an atomization process according to the spray-generation conditions and the evolution along spray downstream, variational features in the velocity and size of droplets obtained through Dual-mode Phase Doppler An 799emometry (DPDA) are delineated and discussed together with instantaneous plane images captured by using Nd:Yag laser sheet beam. A categorization of spray-flow regime representing the atomization and turbulent nature is made through evaluating the non-dimensional parameters, i.e., Reynolds number and Weber number based upon the theoretical injection velocity. These qualitative and quantitative data of spray breakup will be a firm basis for the design of brand-new thruster

• Journal of the Korean Society of Visualization
• /
• v.19 no.2
• /
• pp.41-47
• /
• 2021

River and stream are the important water supply source in our lives. Eutrophication causes excessive green algae growth including microcystis, which makes harmful to ecosystem and human health. Therefore, the water purification process to remove green algae is essential. In Korea, green algae alarm system exists depending on the concentration of green algae cells in river or stream. To maintain the growth amount under control, green algae monitoring system is being used. However, the unmanned, small and automatic monitoring system would be preferable. In this study, we developed the 3D printed device to measure the concentration of green algae cell using microfluidic droplet generator and deep learning. Deep learning network was trained by using transfer learning through pre-trained deep learning network. This newly developed microfluidic cell counter has sufficient accuracy to be possibly applicable to green algae alarm system.

• Korean Chemical Engineering Research
• /
• v.56 no.4
• /
• pp.585-591
• /
• 2018

Characteristics of nano-structured $SiO_2:Zn$ hollow powders prepared in the micro drop fluidized reactor process were investigated with respect to bandgap energy and surface activity. The $SiO_2:Zn$ hollow powders were successfully prepared continuously in the one step process with reasonable production efficiency, with varying the amount of THAM (tris(hydroxymethyl)-aminomethane) additive and concentration of $Zn^{2+}$ ions. The doping of $Zn^{2+}$ ions into $SiO_2$ lattice led to the reduction of bandgap energy by forming the acceptor level of $Zn^{2+}$ below the conduction band of $Si^{4+}$ ions. The hollow shape also contributed to reduce the bandgap energy of $SiO_2:Zn$ powders. The doping of $Zn^{2+}$ ions into $SiO_2$ hollow powders could enhance the surface activity by forming SiO-H stretching and oxygen vacancies at the surface of $SiO_2:Zn$ powders.

• Plant Journal
• /
• v.18 no.1
• /
• pp.50-54
• /
• 2022

The demand for high-efficiency dust collectors is rapidly increasing to remove PM from exhaust gas emission facilities, such as thermal power plants, steel mills, and industrial cogeneration plants, as the Pmemission standards have been strengthened. In this study, the electrospray is adapted for existing electrosratic precipitator(EP) to remedy its shortcomings and to improve the performance. Electrospray has been mainly used for the purpose of generating very fine droplets, but fir the purpose of EP, the flow rate over 10 mL/min per nozzleis required, and a high flow rate condition of 65 to 200 times is required. The electrospray of high flow rate has a completely different spray shape from the low flow rate condition, and was visualized through various figures such as corona discharge photographs and shadow images.