• Journal of ILASS-Korea
• /
• v.20 no.2
• /
• pp.95-100
• /
• 2015

Lower recirculated gas temperature at EGR system reduces NOx and PM emissions. However, EGR Cooler can be polluted by PM generated from recirculated EGR gas, and it reduces cooling efficiency and the amount of EGR gas simultaneously. The SECFR(Steam EGR Cooler Fouling Remover) system which uses the evaporated washer fluid steam caused by high temperature of EGR gas was manufactured for removing fouling generated on the cooler surface. Since an injection pressure of wind shield washer fluid in the vehicle is approximately 0.5 bar, it is not enough to atomize the injected washer fluid. Thus, it is necessary to apply a method to atomize the washer fluid. In this study, the impinging plate was used to promote the atomization of spray washer fluid for the purpose of apply SECFR system to vehicles and measured the DAR(Droplet Area Ratio) and DUI(Droplet Uniformity Index) through the spray visualization.

• 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.

• Resources Recycling
• /
• v.17 no.6
• /
• pp.79-88
• /
• 2008

This study is the previous stage for the mass production technology development of the nano-sized tin oxide powder by the recycling of the wasted tin metal, and nano-sized tin oxide powder with the average particle size below 50 nm is prepared from the tin chloride solution by the spray pyrolysis process. As the reaction temperature increases from 800 to 850, the average particle size of the generated powder increases from 20 to 30 nm. As the reaction temperature increases to 900, the droplet type is composed of the particles with the average size of the 30 nm. while the average size of the independent particles increases up to $80{\sim}100$ nm and the surface microstructure becomes more solid. Until $900^{\circ}C$, as the reaction temperature increases, the XRD peak intensity increases, while the specific surface area decreases. When the reaction temperature increases to 950, most of the powder appears with the independent type and the average particle size decrease down to 70 nm. The XRD peak intensity greatly decreases and the specific surface area increases almost twice.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.258-258
• /
• 2013

최근 건조 제품의 양질화, 고급화 및 편의화가 요구되어 이를 충족시키기 위한 새로운 건조방법이 계속 개발 되어 왔다. 이러한 방법들 중에서 저온과 진공하에서 건조가 이루어지는 진공 동결 건조는 가장 완벽한 건조 방법으로 최근 실용화 되고 있다. 진공동결건조란 건조의 한 종류로 수분을 함유한 시료를 동결시킨 후 진공펌프를 이용하여 수증기압을 3중점 이하로 낮추어 얼음을 직접 증기로 만드는 승화의 원리에 의해서 얻어진다. 분무진공동결건조의 특징은 (1) 물리적구조의 보존성, (2) 화학적인 안정성, (3) 생물학적인 활동의 보존성, (4) 제품의 높은 복원성 및 재생성이다. 따라서 분무진공동결건조 기술은 크게 진공, 분무, 동결, 건조, 멸균 등과 같은 요소기술의 복합기술이라 할 수 있다. 분말을 제조하기 위해서 진공동결건조 후 분쇄하는 방법을 사용하나 본 방법에서는 정밀화학품 제조를 위해서 분무진공동결건조 방식을 사용한다. 이를 통하여 적당한 크기인 5~10 um의 입경 제조가 가능하고, 공기동력학적인 입경이 기존 방식에 비해 작아서 허파까지의 운반효율이 1.5~2배 우수하다. 화학, 의학 분야에서의 분무동결 건조는 주로 민감한 제품, 즉 생물학적 고유성의 손상 없이 물을 제거하는데 사용되어 영구적으로 저장 가능한 상태로 보관할 수 있으며 물의 첨가로 원상태로 복구할 수 있어서 매우 각광을 받고 있다. 의약용 냉동건조 제품은 항생물질, 박테리아, 혈청, 백신, 검사 약물, 단백질을 포함하는 생물공학 제품들, 세포, 섬유, 화학제품 등이 있으며 주로 vial 또는 ampule 상태로 건조가 이루어진다.본 연구에서는 원료를 $-194^{\circ}C$의 액체질소에 분무시켜 동결된 미립자를 형성한 후 진공 및 저온상태에서얼음의 승화(sublimation)에 기반한 1차 건조와 수증기 탈착(desorption)에 기초한 2차 건조 과정으로 구성된 분무진공동결건조기를 개발하였다. 분무동결 과정의 해석을 통해 2유체식 노즐을 통해 분무된 미세 입경의 액적이 액체 질소 표면까지 도달하는 회수률, 분무 노즐의 위치, 운전 조건 및 용기의 설계의 최적화를 수행하였다. 초기 액적속도, 분무노즐의 높이, 흡입구 추가에 따른 액적 유동 및 회수의 특성을 제시하였으며 이를 통한 분사시스템 고도화 가능성을 제시하였다. 구형의 미세 입자가 적층된 제품의 동결건조 공정의 해석은 흡착승화 모델(sorption sublimation model)을 기반으로 다음과 같은 열전달, 물질전달, 상변화 모델을 고려하여 유도되었다. 분무노즐 및 냉동/진공 배기계 시작품을 개발하여, 표면의 고다공도를 갖춘 입경 3~20 m 정도의 시료를 얻을 수 있으며, 동역학적 입경 5 m 충족함을 확인하였다.

• Journal of the Korean Society of Safety
• /
• v.19 no.2
• /
• pp.61-68
• /
• 2004

The evaporation phenomena of waterr droplet which has sodium acetate trihydrate($CH_3COONa{\cdot}3H_2O$) as a fire suppression additive were studied. Solutions of sodium salt up to 50% and heated stainless-steel surface were used in the experiment. The evaporation process was recorded using a charge-coupled-device camera at 120 frames per second. The average evaporation rate of the sodium acetate trihydrate soluation was lower than that of pure water at a given surface temperature and decreased with the concentration increase due to the precipitation of salt in the liquid film and change of surface tension. The variation of liquied film diameter was measured by time and it was increased by the hot surface temperature increase.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2011.11a
• /
• pp.175-178
• /
• 2011

본 연구에서는 기존의 고압으로 작동되는 고압 미분무 건과는 달리 Twin-Fluid의 Turbulence 및 Break-up 현상 등을 이용하여 저압상태에서 작동하며 경량화 및 소형화에 성공하여 기존 소방관의 진입이 어려운 장소 또는 수원으로부터 멀리 떨어진 곳에서 원활한 소화활동을 위해 개발한 저압용 미분무 건의 성능을 화재소화능력 시험을 통해 입증하였다. 화재 소화능력 시험을 수행한 결과 물과 질소가 Mixing Chmaber 내부에서 혼합되면서 두 유체간의 상호작용 및 운동 에너지으로 인해 물의 액적이 미세하게 Atomizing되어 목재화재는 물론 유류화재의 진압에 있어서도 우수한 성능을 확인할 수 있었다.

• Economic and Environmental Geology
• /
• v.46 no.1
• /
• pp.51-61
• /
• 2013

Researches on the oil recovery enhancement using the nanotechnology has recently been studied in the United States. The previous researches has focused mainly on the flow characteristics of nanoparticles in porous media, and the stability of the nano-emulsion itself. However, the analysis did not deal with the size effects between a nano-emulsion and the pore size which has an important role when nano-emulsion flows in the porous media. In this research, nano-based emulsion was fabricated which is able to be applied for the enhanced oil recovery techniques and its characteristics was analyzed. In addition, in order to identify the characteristics of nano-emulsions flowing through the porous media, the size effect was analysed by filtering test. According to the results, when the emulsion was fabricated, SCA(Silane Coupling Agent) or PVA(Poly Vinyl Alcohol) are added to improve the stability of emulsion. As the ratio of the decane to water increased, the viscosity of emulsion and the droplet size also increased. For the filtering test at the atmospheric conditions, the droplet did not go through the filter; only the separated water from the emulsion was able to be filtered. This phenomenon occurred because the droplet was not able to overcome the capillary pressure. At the filtering test by suction pressure, most of the emulsion was filtered over the filter size of $60{\mu}m$. However, the ratio of filtration was rapidly degraded at less than $45{\mu}m$ filters. This is caused due to deformation and destruction of the droplet by strong shear stress when passing through the pore. The results from the study on the basic characteristic of nano-emulsion and filtering test will be expected to play as the important role for the fabrication of the stable nano-emulsion or the research on the recovery of residual oil in porous media.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.313-316
• /
• 2011

This paper investigates CFD investigation on single phase supersonic nozzle flow and 2-phase subson ic flow prior to rocket nozzle supersonic 2-phase flow with water injection within the flame deflector. Numerical results of supersonic nozzle single phase flow showed no notable unrealistic behavior as it captures the usual shock cell structures. Three-dimensional 2-phase flow analysis has also been performed to verify whether the approach can grab the droplet behavior during cooling by water injection. It is expected these basic studies will enhance the cooling problem analysis of supersonic 2-phase rocket plume in the future.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.175-178
• /
• 2008

Spray characteristics for the simplex atomizer are investigated. The atomizer was tested with kerosene which is generally used as a fuel for gas turbine engines. But it is very difficult and dangerous to measure spray performance. So water is used as a working fluid for measuring the droplet information. In this study, spray visualization was performed by using ND-Yag Laser and droplet size was measured by using PDPA system by using two different working fluid such as water and test fluid # 2 which has similar characteristics of the kerosene. The test results show that SMD of water bigger than test fluid # 2 about 5$\sim$15 mm because surface tension of water is higher by a factor of 3. But the spray angles and the spray shapes have similarity

• Journal of Energy Engineering
• /
• v.18 no.2
• /
• pp.93-100
• /
• 2009

An exergy analysis is carried out for the regenerative wet-compression Brayton cycle which has a potential of enhanced thermal efficiency owing to the reduced compression power consumption and the recuperation of exhaust energy. Using the analysis model, the effects of pressure ratio and water injection ratio are investigated on the exergy efficiency of system, exergy destruction ratio for each component of the system, and exergy loss ratio due to exhaust gas. The results of computation for the typical cases show that the regenerative wet-compression gas turbine cycle can make a notable enhancement of exergy efficiency. The injection of water results in a decrease of exergy loss of exhaust gas and an increase of net power output.