• 한국수소및신에너지학회논문집
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• 제15권1호
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• pp.72-81
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• 2004

Study on the analysis of sodium spray fire using Gaussian drop size distribution, which redistributes a droplet spectrum with given mean diameter if its size classes with critical diameter(D>8mm) occur, was carried out. In this case, the oversized droplets were reduced to a stable diameter. Results calculated by the code using Gaussian drop size distribution were in better agreement with AI experimental results than those of NACOM and SPRAY code. The effect of variance on pressure in the test cell appeared greatly by introducing Gaussian function, which could represent various sodium droplet size distribution. The increase of the variance with mean droplet size resulted had an important effect upon the pressure in the test cell.

• 한국안전학회지
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• 제32권4호
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• pp.16-21
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• 2017

The sprinkler system is a basic fire extinguishing system that uses water as an extinguishing agent. In order to evaluate the fire extinguishing performance of the sprinkler system, information such as the discharge angle, discharge speed, discharge pressure, flow rate, and water droplet size of the installed head are required. However, there is a lack of research on droplets size compared to other requirements. In this study, to evaluate the extinguishing characteristics of sprinkler system, the droplet size distribution was measured for various types of sprinkler heads actually used. The size of the droplet was measured using laser diffraction method. The 50% cumulative volume distribution ($D_{v50}$) according to discharge coefficient(K factor) was $540{\mu}m{\sim}695{\mu}m$ for K50, $542{\mu}m{\sim}1,192{\mu}m$ for K80, $980{\mu}m{\sim}1,223{\mu}m$ for K115 and $1,188{\mu}m{\sim}1,234{\mu}m$ for K202. Based on the measured results, the vaeiance of the droplet particle distribution and the distribution ($D_{v50}$) according to discharge coefficient(K factor) was $540{\mu}m{\sim}695{\mu}m$ for K50, $542{\mu}m{\sim}1,192{\mu}m$ for K80, $980{\mu}m{\sim}1,223{\mu}m$ for K115 and $1,188{\mu}m{\sim}1,234{\mu}m$ for K202. Based on the measured results, the vaeiance of the droplet particle distribution and the Rosin-Rammler index value are presented. As a result of the fire simulation with FDS, it was confirmed that the performance difference occurs according to the water droplet size distribution even when the same amount of water is used. Therefore, the extinguishing performance of the sprinkler system should be evaluated considering the droplet size distribution according to the sprinkler head type.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1300-1308
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• 2000

The objectives of this study was to investigate the spray characteristics of single spray and twin spray in the overlap region such as mean axial velocity, mean radial velocity, mean droplet size and probability density function of droplet size. A phase doppler anemometer was used as the measurement system for droplet size and velocity. In case of single spray, injection pressure was varied from 0.2MPa to 0.7MPa. Mean axial velocity, mean radial velocity and droplet size were decreased as the distance below nozzle tip was increased. In case of twin spray, the spray characteristics were measured by varying the distance between two nozzles from 127mm to 155mm. In the overlap region, the boundary of the overlap region was determined by obtaining the distribution of mean axial and radial velocity. Droplet size was increased as the distance from nozzle tip was increased. It was found that the distribution of droplet size for twin spray in the overlap region was different to single spray.

• 한국자동차공학회논문집
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• 제2권5호
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• pp.11-22
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• 1994

The pupose of this study is to measure droplet size and velocity simultaneously for a transient diesel fuel spray in a quiescent chamber at atmospheric temperature and pressure. Generally, diesel combustion phenomena is mainly governed by characteristics of injection system and fuel spray. Therefore we need to clarify these characteristics for developing more economical diesel systems. In this study, correlation between droplet size and velocity was measured at downstream distance from nozzle. Governing parameters are pump speed and fuel quantity for the detailed nature in this transient diesel fuel spray. It is observed effect to the droplet size and velocity distribution. Velocity(peak, mean, rms), number density and droplet size were investigated simulaneously using PDA in the spray. Various results are presented to illustrate the effects of operation factors and correlation between the droplet diameter and velocity.

• Journal of Biosystems Engineering
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• 제25권1호
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• pp.11-18
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• 2000

In precision chemical application increment of biological efficacy with less chemical is the virtue. spraying rate and droplet size is closely related to biological efficacy. this study was performed to develope a spray-control-system that could control spraying rate and droplet size independently. Twin-fluid nozzles were selected and tested to certify if the nozzles were suitable for the objective of this study. Characteritics of the nozzles i.e., spraying rte and droplet size change u8nder the changes of spraying pressure and air pressure were statistically modeled. The model had I to 1 matching property between dependent variables and independent variables. Using the property and the model, inverse relationship could be determined between variables. A feedback spray control system was developed and tested with predetermined error of 5 % in pressure. The system showed 4 % error in spraying rate and 9 % error in droplets size. Performance of the system could be upgraded by fine tuning but, in practical sense keeping air pressure in the field sprayer was the bottle neck of commercialization of the spray system.

• 한국분무공학회지
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• 제22권1호
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• pp.36-41
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• 2017

The present study investigates the evaporation heat transfer characteristics of nanofluid droplet for different nanoparticle sizes. Also, the heat transfer coefficient was measured at different nanoparticle concentrations during evaporation. From the experimental results, it is found that the evaporation behavior of sessile droplet can be considered as constant radius mode due to pinning effect. The total evaporation time of sessile droplet decreases with nanoparticle size up to 7.9% for 0.10 vol% nanofluid droplet. As nanoparticle concentration increases, the clear difference in heat transfer coefficient is observed, showing that the size effect should be examined. This result would be helpful in designing the correlation between the nanoparticle size and the heat transfer characteristics for various applications.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권4호
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• pp.284-288
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• 2001

Lipid emulsions with saturated triacylglycerols (TAGs) with 4 to 10 carbons in each acyl chain were prepared to study how the oil component alters the stability of the lipid emul-sions when phosphatidylcholines were used as emulsifiers. The average droplet size of the emul-sions became smaller as the chain length of the TAG increased. For a given oil emulsion with smaller droplets was formed with an emulsifier having higher HLB value. The influence of HLB values on the droplet size was biggest for the tributyrin (C4) emulsion. For the tricaprylin(C8) emulsions, droplet size was identical at given emulsifier concentrations regardless of HLB values. The HLB value and the concentration of the emulsifiers also affect the droplet size of the emul-sions. The emulsions with smaller average droplet size were more stable than with bigger size for 20 days. The oil and water (o/w) interfacial tension in inversely proportional to the initial droplet size of the emulsion.

• 한국분무공학회지
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• 제18권1호
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• pp.1-8
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• 2013

In this paper an experimental study is presented to investigate the dynamic behavior of impacting droplet onto a liquid film. The main parameters are the droplet velocity and the thickness of the liquid film. Photographic images are presented to show the formation of crown, central jet and disintegrating droplet from the central jet. The emphasis is on presenting the time evolution of crown diameter, crown height, central jet height and the size of disintegrating droplet from the central jet. The diameter and height of crown are higher for faster droplet and thinner liquid film. On the other hand, the height of central jet are higher for faster droplet and thicker liquid film. The size of disintegrating droplet from the central jet heavily depends on the droplet velocity; Larger droplet is produced with faster falling droplets.

• 생물환경조절학회지
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• 제6권3호
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• pp.183-189
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• 1997

구조와 크기가 각각 다른 12종의 미니 스프링클러를 대상으로 살수입자의 크기에 대한 분두의 구경과 살수압력의 영향을 조사하고 스프링클러 종류별로 각 살수 도달거리에서의 살수입자의 크기를 실험한 결과 다음과 같은 결과를 얻었다. 액분산기를 갖은 미니 스프링클러 살수입자 크기와 분두 구경과의 관계를 분석한 결과, 살수입자의 크기는 스프링클러의 분두 구경 보다는 스프링클러의 구조 특히 액분산기의 형태에 더 큰 영향을 받는 것으로 나타났다. 살수압력이 살수입자의 크기에 미치는 영향을 분석한 결과 살수입자의 크기는 살수압력의 1/3승에 반비례함이 확인되었다. 따라서 임의 압력하에서 살수되는 스프링클러 살수입자의 크기는 특정 압력하의 실험결과로부터 용이하게 예측할 수 있다. 살수입자 도달거리와 살수입자 크기와의 관계는 살수입자 도달거리의 2차 함수에 비례하여 살수입자의 크기가 증가하는 것으로 분석되었다. 시판되고 있는 미니 스프링클러의 대표적인 종류를 이용하여 실험한 스프링클러의 살수입자 도달거리별 살수입자의 크기는 스프링클러 종류에 따라 상당한 차이가 있으나 대체적 크기를 보면 도달거리 1m 이내에서는 100~300$\mu\textrm{m}$, 도달거리 1m~2m 범위에서는 230~470$\mu\textrm{m}$, 도달거리 2~3m 범위에서는 300~770$\mu\textrm{m}$으로 나타났다.

• Journal of Biosystems Engineering
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• 제35권6호
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• pp.443-449
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• 2010

A machine vision-based instrument to measure a droplet size spectrum of a spray nozzle was developed and tested to evaluate its accuracy on measuring spray droplet sizes and classifying nozzle sizes. The instrument consisted of a machine vision, light emitting diode (LED) illumination and a desktop computer. The illumination and machine vision were controlled by the computer through a C++ program. The program controlled the machine vision to capture droplet images under controlled illumination, and processed the droplet images to characterize the droplet size distribution of a spray nozzle. An image processing algorithm was developed to improve the accuracy of the system by eliminating random noise and out-of-focus droplets in droplet images while measuring droplet sizes. The instrument measured sizes of the three different balls (254.0, 497.8 and $793.8\;{\mu}m$) and the measurement ranges were $241.2-273.6\;{\mu}m$, $492.9-529.6\;{\mu}m$ and $800.8-824.1\;{\mu}m$ for 254.0-, 497.84- and $793.75-\;{\mu}m$ balls, respectively. Error of the measured droplet mean was less than 3.0 %. Droplet statistics, $D_{V0.1}$, $D_{V0.5}$ and $D_{V0.9}$, of a reference nozzle set were measured, and droplet size spectra of five spray nozzles covering from very fine to extremely coarse were measured to classify spray nozzle sizes. Ninety percent of the classification results of the instrument agreed with manufacturer's classification. A comparison study was carried out between developed and commercial instruments, and measurement results of the developed instrument were within 20 % of commercial instrument results.