• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.784-787
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• 2003

In this study, water jet etching of aqueous green tape was attempted for processing barrier rib of plasma display panel. This process combines 1) chemical etching between water and aqueous based binder in the tape and 2) mechanical erosion by water jet. Effects of etching parameters such as pressure, temperature and aqueous binder content on the morphology of barrier ribs formed were investigated. The results demonstrated a possibility of processing barrier ribs by water jet etching.

• Water Engineering Research
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• v.3 no.4
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• pp.235-245
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• 2002

In this study, breakwater model which has several outlet pipes to discharge water is settled in the experimental open channel and mean velocity distributions of multi wall jet are measured. The length of flow of flow establishment of wall jet is shorter than that of free jet and decay rate of jet centerline longitudinal velocity along x is linear in 0.3 $\leq$ x/$\l_q$ $\leq$ 17. The rate of vertical width and lateral width spreading of multi wall jet is respectively 0.0753, 0.157~0.190.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.53-60
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• 2001

Water jet cutting is a new technology using very high pressure water as a cutting tool. Water jet cutting system consists of water preparation part, pressure generation pate, cutting head, and motion part. A PC-based numerical controlled (PC-NC) X-Y table is developed and water get cutting system is installed thereon. Water jet machining is applicable to various kinds of materials ranging from soft materials such as rubber and meat to hard-to-cut materials such as titanium. This paper shows the application of the abrasive waterjet system to titanium cutting.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.197-203
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• 2014

The liquid jet breakup has been studied in the areas such as aerosols, spray and combustion. The breakup depends on several physical parameters such as the jet velocity, the nozzle inner diameter, and the density ratio of the water to the jet. This paper deals with characteristics of the jet breakup according to the jet velocity and the nozzle diameter. In order to consider only hydrodynamic factors, all the experiments were conducted in non-boiling conditions. The jet behavior in the water pool was observed by high-speed camera and PIV technique. For the condition of the inner diameter of 6.95 mm and the jet velocity of 2.8 m/s, the debris size of 22 mm gave the largest mass fraction, 39%. For higher jet velocity of 3.1 m/s, the debris size of 14 mm gave the largest mass fraction, 36%. For the nozzle with inner diameter of 9.30 mm, the debris size distribution was different. For jet velocity of 2.8 m/s and 3.1 m/s, the debris size with the largest mass fraction was found to be 14 mm. It was identified that the debris size decreased as the diameter or the jet velocity increased.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.5
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• pp.249-256
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• 2010

Water jet impingement cooling has been widely used in a various engineering applications; especially in cooling of hot steel plate of steelmaking processes and heat treatment in hot metals as an effective method of removing high heat flux. The effects of cooling water temperature on water jet impingement cooling are primarily investigated for hot steel plate cooling applications in this study. The local heat flux measurements are introduced by a novel experimental technique that has a function of high-temperature heat flux gauge in which test block assemblies are used to measure the heat flux distribution during water jet impingement cooling. The experiments are performed at fixed flow rate and fixed nozzle-to-target spacing. The results show that effects of cooling water temperature on the characteristics of jet impingement heat transfer are presented for five different water temperatures ranged from 5 to $45^{\circ}C$. The local heat flux curves and heat transfer coefficients are also provided with respect to different boiling regimes.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.16-17
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• 2006

In order to obtain spherical fine powder, we have developed a new method of high-pressure water atomization system using swirl water jet with the swirl angle $(\omega)$. The effect of nozzle apex angle $(\theta)$ upon the morphology of atomized powders was investigated. Molten copper was atomized by this method, with $\omega=0.2$ rad (swirl water jet) and $\omega=0$ rad (conical water jet). It was found that the median diameter $(D_{50})$ of atomized powders decreased with decreasing $(\theta)$ down to 0.35 rad in each $\omega$, but under ${\theta}<\;0.35$ rad, $D_{50}$ increased abruptly with decreasing $\theta$ for $\omega=0$ rad, while it was still decreased with decreasing $(\theta)$ for $\omega=0.2$ rad.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.611-617
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• 1989

A jet cutting system is a new concept of cutting device wihch requires high pressure up to thousands of atmospheric pressure. The use of water as a cutting medium brings in many of working advantages such as no dust, no gas, and no thermal distortion. And an introduction of abrasives into the water jet flow increases signigicantly cutting abilities and improves cutting performance. Cutting with abrasive water jet involves many operating variables, including design of the cutting system. For efficient cutting, the operating parameters have to chosen properly. In spite of several attempts to develop the cutting model theoretically, all of the optimization of the operating parameters is based upon exerimental results of each jet cutting system. In this paper, the effect of the parameters was measured and analysed in terms of pressure, abrasive, and transverse rate of a workpiece. Most of all, sufficient feeding of abrasives is the most important factor for efficient cutting performance.

• Journal of the Korean Wood Science and Technology
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• v.32 no.3
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• pp.1-7
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• 2004

The application of abrasive-assisted high energy water-jet was investigated as a possible new method of cutting wood. In this study the maximum cutting speeds for species of various wood density were determined and water-jet machining characteristics were investigated for sixteen Korean domestic species. The maximum cutting speed ranged from 200 to 750 mm/min. The results indicate that wood density affects machining characteristics such as maximum cutting speed, surface roughness, and kerf width. Roughness of surface generated increased and kerf width decreased as penetration depth increased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.4
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• pp.527-536
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• 1996

Convective nucleate boiling and burnout heat flux have been studied on a flat, downward facing, constant heat flux surface cooled by an impinging water jet. The tests are progressed from low, nonboiling power to high, burnout heat flux power. The jet velocity and the subcooling do not affect the nucleate boiling curve of $q{\sim}{\Delta}T_{sat}$ diagram, but the supplementary water height affects the curve. For the case of dimensionless height of supplementary water S/D=1, the boiling curve shift to the heigher heat flux than that of S/D=0 or S/D=2. Burnout heat flux is enhanced with increasing jet velocity and subcooling. Also. by using the supplementary water(S/D=1 or S/D=2), burnout heat flux is larger than that of the simple water jet(S/D=0). A generalized correlation for the burnout heat flux data in the present boiling system with an impinging water jet is successfully evolved.

• Journal of the Semiconductor & Display Technology
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• v.8 no.2
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• pp.31-35
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• 2009

In the silicon wafer polishing process, the mounting stage of silicon wafer on the ceramic carrier block has been using the polishing template which utilizes the porous surface instead of traditional wax mounting method. Here in this article, the experimental study is carried out in order to study the wafer demounting by water jet and the effects of operating conditions such as the water jet flowrate and the number of water jet nozzles on the wafer demounting time. It is found that the measured wafer demounting time is inversely proportional to the water flowrate per nozzle, regardless of number of nozzles used; implying that the stagnation pressure by the water jet impingement is the dominant key factor. Additionally, by using the transparent disk instead of wafer, the air bubble formation and growth is observed under the disk, making the passage of water flow, and subsequently demounting the wafer from the porous pad.