• 한국생산제조학회지
• /
• 제22권5호
• /
• pp.767-773
• /
• 2013

A high-pressure, high-pressure drop control valve, which transforms the power transfer of a system by reducing the inlet pressure of 345bartothe outlet pressure of 112bar, is a fundamental component in an offshore plant process. With the increasingly growing market share of the maritime industry, this valve has been expected to be a high-value-added product. This study not only analyzes the relation between pressure drop and fluid velocity in a trim by using fluid analysis, but also examines the possibility of cavitation in a valve in addition to the plot for the extension of lifespan. Based on the analysis results, the design and production method of the valve are established, and accordingly, performance evaluation is carried out. It is demonstrated that the pressure drop from 345bar to 112bar is more feasible in the presence of the trim, which can induce a continuous and diminutive pressure drop in order to prevent cavitation in a high-pressure drop control valve. Furthermore, despite the fluid velocity near a seatring being found to be over 30m/s, the lifespan of the valve is determined to be adequate considering the operation condition of a prototype valve of 80%.

• 한국유체기계학회 논문집
• /
• 제5권1호
• /
• pp.20-26
• /
• 2002

This study reports the analysis of the pressure drop characteristics for the air-particle flow in powder transport piping system. The pressure drop characteristics of air-particle flow in piping system is not well understood due to the complexity of particles motion mechanism. Particles or powders suspended in air flow cause the increase of the pressure drop and affect directly the transportation efficiency. In this study, the pressure drop in powder transport piping system with straight and curved pipes is analyzed for the interactions of air flow and particle motion. The total pressure drop increases with increasing of the pipe length, the mixture ratio, and the friction factor of particles due to the increasing friction loss by air and particles in a coal piping system. For the coal powders of $74{\mu}m$ size and powder-to-air mass mixture ratio of 0.667, the total pressure drop by the consideration of powders and air flow is $30\%$ higher than that of air flow only.

• 반도체디스플레이기술학회지
• /
• 제9권1호
• /
• pp.23-28
• /
• 2010

In this paper, wafer drop from wafer guide mechanism, which is one of the serious problems in water transfer robot, is analyzed, and new wafer guide mechanisms are proposed to minimize this drop. Three types of new wafer guide mechanisms are proposed: roller type, gear type and L-shape rocker type. We choose one of the proposed mechanism, which is roller type, and verified this mechanism through real transfer experiment. Wafer picking up test is conducted with initial aligning error for simulating the wafer drop. Number of drop is compared between conventional mechanism and proposed mechanism. As a result, we can find the proposed mechanism can reduce the number of wafer drop dramatically.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2007년도 하계학술발표회 논문집
• /
• pp.365-366
• /
• 2007

Micro jetting drop inspection system is essential to measuring micro drop volume. Measuring pico-liter drop volume is useful for new LCD color filter product process that is based on inkjet printing technology. To upgrade the reliability in drop measurement system, we use the auto focusing & multi drop reiteration & blurring average algorism. First of all we used standard mark for gage R&R in the vision system. Finding the most suitable threshold for multi blurring drop, is the main key of this research. Sensitivity of vision system is a standard in measuring the upgrade system level. So, suitable threshold can upgrade the performance of jetting drop inspection system.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.2995-3000
• /
• 2008

Understanding of the impinging behavior of an electrically charged spray is essential in determining appropriate operating conditions for electro-spraying of paints, surface coating materials and insecticides. In the present work, the wall impact behavior of an electrically charged drop has been investigated and compared with that of a neutral drop experimentally. The critical Sommerfeld number representing the spread-splash boundary for the charged drop impacting on the dielectric substrate turned out to be larger compared to that for the neutral drop with the same surface condition. The change of the transition boundary is due to the increase in the surface wettability of the drop on the substrate. However, with the electrically conducting substrates, the charging effect on the transition boundary appeared negligible. This is because the electric discharging time is much shorter than the time required for the flattened drop to reach its maximum extent.

• 설비공학논문집
• /
• 제15권6호
• /
• pp.510-517
• /
• 2003

An experimental study on the pressure drop during flow boiling for pure refrigerants R134a and Rl23, and their mixture was carried out in a uniformly heated horizontal tube. Tests were run at a pressure of 0.6 MPa and in the ranges of heat flux 5~50 kW/m$^2$, vapor quality 0~100 percent and mass velocity of 150~600 kg/m$^2$s. Generally, the two-phase frictional multiplier is used to predict the frictional pressure drop during the two-phase flow boiling. The obtained results have been compared to the existing various correlations for the two-phase multiplier. Also, the frictional pressure drop was compared to a few available correlations; The Lockhart-Martinelli correlation considerally overpredicted the frictional pressure drop data for mixture as well as pure components in the entire mass velocity ranges employed in the present study, while the Chisholm correlation underpredicted the present data. The Friedel correlation was found to satisfactorily correlate the frictional pressure drop data except for a low quality region.

• 한국가구학회지
• /
• 제21권3호
• /
• pp.253-260
• /
• 2010

The drop handle in the Chosun-Dynasty played a role lifting up the cabinet and box which was attached to and besides this had the decoration function. The scope of this study should include the drop handles from the $18^{th}$ century up to now by investigating and analyzing their definition & function and furthermore the types of their designs. The object of the study was the drop handle having 2 golden fixing parts which are definitive difference from ring or loop, and the design typology of drop handle was concentrated on the handle part, and it can be classified in two types. The one is the figuration of bow, bat, bamboo, fish and bird and so on from the motive of nature on the handle part, and the other one is the drop handle of the simple ㄷ-shape, the temple-symbol shape or geometrical forms. According to the analysis of relics & literature from the past it was found that there were more quantitative nature-motive figurations than the geometrical forms. The nature-motive figurations were again classified in box-, bat-, cloud- bamboo-, fish- and bird-type, and the geometrical forms in ㄷ-shape, the temple-symbol shape and others. The cases applied to furniture are roughly divided into the front-attached type and the side-attached type. In comparison of the drop handle in the Chosun-Dynasty with that of modern times, ㄷ-shape and bow-type keep the long tradition of the drop handles despite of the constructive change partly. Ring-type is similar to the just ring or loop of the part and drop handle with one golden fixing part, while the knob-type shows almost same forms in the past as well as in the modern times. Which type among handles in the modern times has little connection with the past is the reclaimed type, and it was showed in the Chosun-Dynasty and also is showed up to now identically that the man-made hole on the front side of the drawer for the function as handle.

• 수산해양교육연구
• /
• 제14권2호
• /
• pp.177-190
• /
• 2002

An experimental study was carried out to make clear heat transfer characteristics in flow boiling of binary mixtures of refrigerants R134a and R123 in a uniformly heated horizontal tube. Experiments were run at a pressure of 0.6 MPa both for pure fluids and mixtures in the ranges of heat flux $10{\sim}50{kW/m}^2$, vapor quality 0~100% and mass flux 150-600 $kg/m^2s$. Heat transfer coefficients of mixtures were reduced compared to the interpolated values between pure fluids both in the low quality region where the nucleate boiling is dominant and in the high quality region where the convective evaporation is dominant. Total pressure drop during two-phase flow boiling in a horizontal tube consists of the sum of two components, that is, the frictional pressure drop and pressure drop due to acceleration. The frictional pressure drop is the most difficult component to predict, and makes the most important contribution to the total pressure drop. On the other hand, the acceleration pressure drop resulting from the variation of the momentum flux caused by phase change is generally small as compared to the frictional pressure drop. There is no significant difference in measured pressure drop between mixtures and pure fluids. The correlation of Martinelli and Nelson predicted most of the present data both for pure and mixed refrigerants within 30%.

• 항공우주시스템공학회지
• /
• 제18권3호
• /
• pp.56-64
• /
• 2024

본 연구에서는 항공우주구조물의 낙하 충격 특성 및 기초 시험, 학술적 연구를 종합적으로 수행하기 위하여 낙하충격시험기를 개발하였다. 낙하충격시험기는 항공기가 지면과의 충돌 시 발생하는 동적인 응력과 변형에 대한 정확한 평가를 가능하게 하며, 안전성 및 기구 강도와 같은 중요한 설계 요소들을 확인할 수 있도록 한다. 낙하충격시험기는 전자석을 이용하여 시험체를 부착 및 낙하하며, 크레인을 이용하여 시험체 낙하 높이 조절이 가능하도록 구성하였다. 또한, 수직 낙하를 위한 낙하보조장치를 제작하였다. 시험을 위한 낙하 시험체의 수치해석을 수행하고 낙하충격시험기를 활용하여 기초 시험을 수행하였다. 해석 및 시험 결과를 통해 착륙장치 낙하 상황에서의 구조적 형상을 분석하고 각 부분의 거동을 종합적으로 평가하였다.

• 한국전산유체공학회지
• /
• 제21권4호
• /
• pp.90-95
• /
• 2016

Leidenfrost drops with ellipsoidal shaping can control the bouncing height by adjusting the aspect ratio(AR) of the shape at the moment of impact. In this work, we focus on the effect of the AR and the impact Weber number(We) on the non-axisymmetrical spreading dynamics of the drop, which plays an important role in the control of bouncing. To understand the impact dynamics, the numerical simulation is conducted for the ellipsoidal drop impact upon the perfect non-wetting solid surface by using volume of fluid method, which shows the characteristics of the spreading behavior in each principal axis. As the AR increases, the drop has a high degree of the alignment into one principal axis, which leads to the consequent suppression of bouncing height with shape oscillation. As the We increases, the maximum spreading diameters in the principal axes both increase whereas the contact time on the solid surface rarely depends on the impact velocity at the same AR. The comprehensive understanding of the ellipsoidal drop impact upon non-wetting surface will provide the way to control of drop deposition in applications, such as surface cleaning and spray cooling.