• 대한기계학회논문집B
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• 제30권12호
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• pp.1236-1242
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• 2006

The local heat flux of spray cooling in the film boiling region were experimentally investigated for the spray region of $D_{max}$ = $0.005{\sim}0.03m^3/(m^2s)$. A twin-fluid full cone spray nozzle was employed for the experiment and the distributions of droplet flow rates were obtained for air-water full cone sprays. A stainless steel block was cooled down from initial temperature of about $800^{\circ}C$ by full cone spray. In the region near the stagnation point, it was found that the experimental data are in good agreement with the results predicted from the correlations between the local heat transfer and the local droplet flow rate proposed in the previous report. However, it was found that the experimental data of $D_r$ > $0.01m^3/(m^2s)$ are a little smaller than the results predicted from the correlations.

• 한국분무공학회지
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• 제16권1호
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• pp.27-36
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• 2011

The impact force on the single and overlap region of twin spray was experimentally evaluated using visualization method in full cone type swirl nozzle spray. Visualization of spray was conducted to obtain the spray angle and breakup process. The photography/imaging technique, based on Particle Image Velocimetry (PIV) using high-speed camera, was adopted for the direct observation of droplet motion and axial velocity measurement, respectively. Droplet size was measured by Particle Motion Analyze System (PMAS). The purpose of this study is to provide fundamental information of spray characteristics, such as impact force, for higher etching factor in the practical wet etching system. It was found that the spray angle, axial velocity and impact force were increased with increasing the nozzle pressure while droplet size decreased with increasing the nozzle pressure. Droplet size increased as the distance from nozzle tip was decreased. The impact force of twin spray in the overlap region was about 63.29, 67.02, 52.41% higher than that of single spray at 40, 50 and 60 mm of nozzle pitch, respectively. Also, the nozzle pitch was one of the important factors in the twin spray characteristics.

• 한국분무공학회지
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• 제13권3호
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• pp.143-148
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• 2008

In the present study, the correlation between the Nusselt number and Reynolds number was developed for forced convection and nucleate boiling region in spray cooling. Also the effect of droplet subcooling on spray cooling heat transfer was investigated. Full cone spray nozzles were employed for spray cooling experiment, and water and FC-77 were used for developing the correlation. From the experimental results, the correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30%$ error for water and FC-77.

• 한국분무공학회지
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• 제14권4호
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• pp.178-183
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• 2009

Spray cooling heat transfer was experimentally investigated for water sprays impacting on mico-fins structured surfaces in the single phase and nucleate boiling regions. The heat transfer surfaces consist of cubic fins and triangular grooved fins. The spray produced using full cone spray nozzles, and experiments were made under the test condition of $Q=4.92{\times}10^{-6}{\sim}15.83{\times}10^{-6}\;m^3/s$, $T_f=35{\sim}55^{\circ}C$. From the experimental results, it was found that cubic fins surface had the largest heat flux enhancement relative to the smooth surface.

• 설비공학논문집
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• 제22권1호
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• pp.33-39
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• 2010

The film boiling heat transfer was experimentally investigated for the water sprays impacting on an inclined hot surface. Full cone spray nozzles were employed for the spray cooling experiment, and experiments were made for different inclination angles of $\theta=0^{\circ}$, $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$. The experimental results show that, in the downstream region of the inclined hot surface, increasing the inclination angle increases the local heat flux slowly because of increasing the number of rebound droplets. However, the inclination angle of heat transfer surface had no remarkable effect on the local heat flux of spray cooling under the present test conditions.

• 한국분무공학회지
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• 제12권4호
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• pp.179-184
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• 2007

The boiling heat transfer was experimentally investigated for the FC-77 sprays impacting a square heated test surface in a downward direction. Full cone spray nozzles were employed for the spray cooling experiment, and experiments were made under the test conditions of $Q=3.32{\times}10^{-6}{\sim}2.30{\times}10^{-5}\;m^3/s$, ${\Delta}T_{sub}=20{\sim}70^{\circ}C$. Also, heat transfer measurements were made using the copper block of $10{\times}10\;mm^2$ test area heated by nine cartridge heater. From the experimental results, correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30%$ error for FC-77.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.199-210
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• 1998

The skill that utilizes atomization of the liquid has been widely used in the field of industry and engineering. Though there are dozens of methods to make atomization, the pressure type injection nozzle is frequently used in washing of parts, pastourization and painting because it has relatively simple system. This study is to reveal the characteristics of atomizing formed by three different types of the pressure type injection nozzle. We measured velocity and diameter of droplet to compare and analyze characteristic of each nozzle. In case of velocity, atomization of hollow-cone nozzle is irregular than others and change of radial direction is especially large. Atomization of flat nozzle is nearly uniform. In case of diameter, atomization of hollow-cone nozzle is increased rapidly, as measurement point become more distant from the center of nozzle. Atomization of flat nozzle has the most fixed magnitude. Accordingly, full-cone nozzle can be used irrespective of the form of subject and hollow-cone nozzle is proper to the occasion to spray large and smooth subject. Also, flat nozzle is proper to the occasion to spray a part of subject and long groove.

• 한국화재소방학회논문지
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• 제33권5호
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• pp.28-36
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• 2019

본 연구에서는 분사 형태(Spray pattern)가 중실원추형(Full cone) 및 중공원추형(Hollow cone)인 2유체 미립화기를 이용하여 공급 기체 및 미분무가 헵탄 풀화재(Heptane pool fire) 소화 성능에 미치는 영향을 검토하였다. 2유체 미립화기의 공급 기체로 30 lpm (Liter per minute; L/min)의 공기 또는 질소를 이용하였으며, 물을 공급하지 않은 경우(즉, 공기 또는 질소만 분사한 경우)와 물 0.085 lpm을 공급한 경우(즉, 미분무와 공급 기체를 함께 분사한 경우)에 대해 실험을 수행하였다. 실험 결과, 공급 기체만 분사한 경우보다 미분무와 공급 기체를 함께 분사한 경우에, 그리고 중공원추형인 경우보다 중실원추형인 경우에 빠르게 화재 소화 가능함을 확인하였다. 또한, 중실원추형의 경우, 미분무와 공급 기체 함께 분사 시 화재 소화 성능에 미분무의 영향은 지배적이었으나 공급 기체의 영향은 미비한 것으로 관찰되었다. 반면, 중공원추형의 경우, 중실원추형과 달리 미분무와 공급 기체 함께 분사 시 공급 기체로 질소를 공급한 경우가 공기를 공급한 경우에 비해 평균 화재 소화 시간이 확연하게 짧아지는 것으로 측정되었고, 이를 통해 미분무 뿐 아니라 공급 기체도 화재 소화 성능에 지대한 영향을 미칠 수 있음을 확인하였다.

• 대한기계학회논문집B
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• 제32권12호
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• pp.938-944
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• 2008

The boiling heat transfer was experimentally investigated for the PF-5052 sprays impacting a square heated test surface in a downward direction. Full cone spray nozzles were employed for the spray cooling experiment, and experiments were made under the test conditions of Q=$3.32{\time}10^{-6}{\sim}\;12.98{\time}10^{-6}m^3/s$, ${\Delta}T_{sub}=5{\sim}25^{\circ}C$. Also, heat transfer measurements were made using the copper block of $10{\time}10mm^2$ test area heated by nine cartridge heater. From the experimental results, correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30$ % error for PF-5052.

• 한국전산유체공학회지
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• 제11권4호
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• pp.56-61
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• 2006

Numerical simulation has been performed to investigate the characteristics of the mist flow through the fire suppression nozzles. The commercial CFD software, FLUENT with the proper modeling was applied for analyzing both the internal and external flow of the spray nozzles. Computations were made for the full cone nozzle in the operation range of the low pressure and high flow-rate. To validate the present computational procedure, numerical results are compared with measurements in terms of K-factor, SMD, axial spray velocity and spray angles. Numerical results suggested that the present numerical model can be used as an adequate tool for a design purpose of mist-spray nozzles.