• 한국분무공학회지
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• 제6권1호
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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.

• 생물환경조절학회지
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• 제21권3호
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• pp.163-169
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• 2012

관비재배 및 수경재배시 비료를 녹일 때 소요되는 시간과 노동력을 절감하고, 작업의 안전성 확보와 자동화를 가능하게 할 수 있는 장치의 개발을 위해 본 실험을 실시하였다. 실험은 세 종류로 수행되었다. 먼저, 효과적인 비료용해 방법을 구명하기 위해 수중펌프를 양액 통 속에 두고 양액 통의 입구에 삼베포를 깐 거름망을 설치하여 물을 스프레이하여 비료를 녹이는 방법(Spray), 수중프로펠러를 이용하는 방법(Propeller), 수중펌프를 양액 통 속에 넣어 물의 흐름을 만들어 주는 방법(Submerged), 에어컴프레서를 이용하여 양액 통 속에 공기흐름을 만들어 비료를 용해하는 방법(Airflow) 등 4개의 처리를 두고 실험하였다. Spray 처리에서 가장 시간이 짧게 소요되는 것으로 조사되었으나 농가가 실제로 적용하는데 어려움이 있어서, Spray 처리 다음으로 비료를 녹이는 시간이 짧고, 노동력을 절감할 수 있으며 양액제조 과정을 자동화 하는 것이 용이할 것으로 사료되는 Airflow 처리를 선택하였다. 두 번째 실험에서는 Airflow 처리에서 사용한 재질과 분지관수를 개선한 6지관 및 8지관 장치를 제작하여 비교 실험했는데, 6지관 장치가 비료용해시간이 짧고, 양액탱크의 입구 크기에 관계없이 사용이 가능하며, 제작이 용이하여 가장 효과적인 장치로 판단되었다. 세 번째 실험에서는 개발된 6지관 장치를 이용하여 비료를 용해하는데 소요되는 시간을 조사하여 경제성을 분석하였는데, 농가에서 수중펌프를 이용하여 비료를 용해하는 방법보다 시간은 1/8배 절약할 수 있으며 경제성이 큰 것으로 나타났다. 아울러 $KNO_3$, $Ca(NO_3)_2{\cdot}4H_2O$, Fe-EDTA 등의 용해특성을 조사했다.

• 한국분무공학회지
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• 제19권1호
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• pp.19-24
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• 2014

In this study, the cooling performance of a liquid CPU cooler using the water/propylene glycol(PG)-based $Al_2O_3$ nanofluids is experimentally investigated. Water/PG-based $Al_2O_3$ nanofluids are manufactured by two-step method with ultrasonic energy for 10 hours. The volume fractions of the nanofluids are 0.25% and 0.35%. Thermal conductivity and viscosity of the nanofluids are measured to theoretically predict the thermal performance of the liquid CPU cooler using performance factor. Performance factor results indicate that the cooling performance of the liquid CPU cooler can be improved using the manufactured nanofluids. To evaluate the cooling performance of the liquid CPU cooler experimentally, temperature differences between ambient air and heater are measured for base fluid and nanofluids respectively. Based on the results, it is shown that performance of the liquid CPU cooler using $Al_2O_3$ nanofluids is improved maximum up to 8.6% at 0.25 Vol.%.

• 한국분무공학회지
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• 제20권1호
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• pp.53-58
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• 2015

In this study, we prepare the Ag nanofluids synthesized by the chemical reduction method and measure the extinction coefficient of those nanofluids at a wavelength of 632.8 nm. The Ag nanofluids are synthesized by the chemical reduction method using silver nitrate ($AgNO_3$) and sodium borohydride ($NaBH_4$) in water and ethylene glycol (EG). For stable dispersion of Ag particles in the base liquids, polyvinyl pyrrolidone (PVP) is added as a surfactant. The extinction coefficient of manufactured Ag nanofluids is measured by an in-house developed measurement system at the wavelength of 632.8 nm. The results show that the extinction coefficient of water-based and EG-based Ag nanofluids is linearly increased with respect to the particle loadings. Moreover, it is shown that the extinction coefficient of EG-based Ag nanofludis is higher than that of water-based Ag nanofluids. Finally we compare the experimental results with both the Maxwell-Garnett model and Rayleigh scattering approximation model, and they demonstrate that the Rayleigh scattering approximation model is reasonably predict the extinction coefficient of Ag nanofluids using hydraulic diameter of silver nanoparticle.

• International Journal of Fluid Machinery and Systems
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• 제9권4호
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• pp.287-299
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• 2016

In China, agricultural irrigation water often contains a lot of suspended sediment which may cause the nozzle wear. In this study, a new numerical simulation combing the Discrete Phase Model and a remeshing algorithm was conducted. The geometric boundary deformation caused by the erosion wear, was considered. The weight loss of the nozzle, the node displacement and the flow field were investigated and discussed. The timestep sensitivity analysis showed that the timestep is very critical in the erosion modeling due to the randomness and the discreteness of the erosion behavior. Based on the simulation results, the major deformation of the boundary wall due to the erosion was found at the corners between outlet portion and contraction portion. Based on this remeshing algorithm, the simulated erosion weight loss of the nozzle is 4.62% less compared with the case without boundary deformation. The boundary deformation changes the pressure and velocity distribution, and eventually changes the sediment distribution inside the nozzle. The average turbulence kinetic energy at the outlet orifice is found to decrease with the erosion time, which is believed to change the nozzle's spray performance eventually.

• 한국분무공학회지
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• 제13권4호
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• pp.187-192
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• 2008

In this study, the mechanisms of binary droplet collision were studied with diesel, ethanol and purified water. The droplet collisions of liquid droplet have been investigated for the same droplet diameter. In order to obtain the digital images of the droplet collision behavior, the experimental equipment was composed of the droplet generating system and the droplet visualization system. The droplets were produced by the vibrating orifice monodisperse generator. The visualization system consisted of a long distance microscope, a light source, and a high speed camera. The outcomes of binary droplet collision can be divided into four regimes, bouncing, coalescence, reflexive separation and stretching separation. The impact angle and the relative velocity of binary droplet are main parameters of collision phenomena, so the transition mechanism of droplet collision can be divided by the impact parameter.

• 한국분무공학회지
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• 제11권2호
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• pp.98-104
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• 2006

A charged droplet scrubber was introduced to remove visible smokes generated in many industrial facilities. Lab-scale and field tests were conducted in this study. The system consists of a corona discharger to effectively charge the fine particles, fellowed by an electrostatic chamber to promote coagulation between charged fine particles and oppositely charged droplets and a demister to remove resultant particles. Overall collection efficiency, 98.4% was obtained from a lab-scale test, when a high voltage was applied to an ionizer and a charged droplet scrubber. Field tests also show the high collection efficiencies, 93.5% with one stage and 99.4% with two stage system. This system can be used to increase the collection efficiency of the conventional air pollution control devices to satisfy the national emission standard.

• 한국분무공학회지
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• 제9권3호
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• pp.29-34
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• 2004

To investigate characteristics and micro-explosion of single-droplets of emulsified fuel, water is mixed with diesel oil by using ultrasonic energy fuel feeding system. The fuel characteristics is analysed through H-NMR spectrum and micro-explosion phenomena of the emulsified fuel is also investigated. The life times of droplets of conventional diesel fuel, ultrasonic energy added diesel fuel and emulsified fuel we obtained additionally. According to this study, the micro-explosion phenomena of single-droplets happen in atmospheric pressure condition, a curve form of emulsified fuel's life tim is different from diesel fuel's one and the change of chemical structures is a cause of ultrasonic-energy-added diesel fuel effect.

• 한국분무공학회지
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• 제25권2호
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• pp.68-73
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• 2020

In the present study, experiments on the film boiling of liquid droplets on oxidized copper surface was conducted. The shape of pure water droplets was observed, and the evaporation rate of them was measured during the film boiling evaporation process. The droplet of initial volume 16 ~ 30 µl was applied onto the oxidized copper surface heated up to 300 ~ 500℃, then the shape of the droplet was analyzed during the film boiling evaporation. Experimental results showed that there was good correlation between dimensionless volume and dimensionless time. However, a significant difference in evaporation rate for small and large droplets discussed in previous study was not found.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.253-256
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• 2006

This paper shows the study on application of the law temperature energy in the deep seawater. Deep, cold seawater has long been recognized as a valuable ocean energy resource. Recently, research and experimentation has been conducted on energy systems using deep seawater: deep seawater air conditioning system, ice-making device, salt and fresh-water manufacturing system and the Spray freeze drying system for extracting valuable material of the deep seawater. They are technically and economically feasible today: once installed, the energy is inexhaustible and there are no adverse environmental impacts. Because of the economy of scale in the air conditioning system, the seawater A/C system is most appropriate for supplying multiple buildings or hotels in a coastal area.