• 유공압시스템학회논문집
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• 제4권1호
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• pp.1-6
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• 2007

The typical hydraulic system of hoist is composed of a hydraulic supply unit, a directional control valve, two pilot operated check valves, two flow control valves. The capacity coefficients of flow control valves should be adjusted for the hoist to operate at moderate speed and minimize the hydraulic energy loss. However, it is difficult to adjust the four capacity coefficients of flow control valves by trial and error for optimal operation. The steady state model of the hoist hydraulic system is derived and the optimal capacity coefficients of flow control valves are obtained using the complex method that is one kind of constrained direct search method.

• 에너지공학
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• 제24권2호
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• pp.103-109
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• 2015

배열회수 보일러는 입구 확관 덕트와 전열관군으로 이루어져 있는데 전열관군에서 열전달 효율을 향상하기 위해서는 전열관군 전에서 배기가스 유동이 균일하게 되어야 한다. 본 연구에서는 전열관군 전의 배열회수 보일러 입구 덕트에서 유동 특성을 살펴보았고 전열관군의 열전달 메커니즘을 지금까지 다른 연구들에서 적용하였던 일정한 열전달 량으로 한 경우와 전열관군 배관의 내부와 외부의 대류열전달을 고려한 열전달 메커니즘을 적용한 경우의 해석에서 온도 분포를 비교하여 배열회수 보일러의 전열관군에서 실제 현상에 보다 적합한 열전달 메커니즘을 정립하는 것을 목적으로 하였다. 본 연구를 통하여 전열관군 배관의 내부와 외부의 대류열전달을 고려한 열전달 메커니즘을 적용한 해석이 일정한 열전달 량을 적용한 경우보다 온도 분포가 타당한 결과를 도출하였고 이렇게 적용한 경우는 배열회수 보일러 탈질설비 전단에서 온도 분포가 설계 기준 ${\pm}10^{\circ}C$에 만족함을 알 수 있었다.

• Wind and Structures
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• 제9권1호
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• pp.23-35
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• 2006

The effect of buildings on flow in urban canopy is one of the most important problems in local/micro-scale meteorology. A large eddy simulation model is used to simulate the flow structure in an urban neighborhood and the bulk effect of the buildings on surrounding flows is analyzed. The results demonstrate that: (a) The inflow conditions affect the detailed flow characteristics much in the building group, including: the distortion or disappearance of the wake vortexes, the change of funneling effect area and the change of location, size of the static-wind area. (b) The bulk effect of the buildings leads to a loss of wind speed in the low layer where height is less than four times of the average building height, and this loss effect changes little when the inflow direction changes. (c) In the bulk effect to environmental fields, the change of inflow direction affects the vertical distribution of turbulence greatly. The peak value of the turbulence energy appears at the height of the average building height. The attribution of fluctuations of different components to turbulence changes greatly at different height levels, in the low levels the horizontal speed fluctuation attribute mostly, while the vertical speed fluctuation does in high levels.

• 한국콘텐츠학회논문지
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• 제16권4호
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• pp.614-623
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• 2016

스마트워터그리드의 중요한 요소기술로써 그리드(관망)의 설계는 압력, 마찰계수, 마찰속도, 수두손실, 그리고 에너지 경사와 같은 수리학적 매개변수를 추정하는 것이 필수적이다. 특히, 그리드의 마찰속도는 에너지 경사, 마찰계수, 압력, 수두손실 등의 결합에 있어 매우 중요한 인자이다. 그러나 마찰 수두손실, 마찰속도 등 마찰인자를 정확히 산정하는 것은 매우 어려우며, 경험적 마찰 인자는 여전히 약 100년 전에 개발된 공식과 이론을 사용함으로써 산정된다. 따라서, 본 논문에서는 최대유속과 마찰속도 사이의 새로운 공식을 Darcy-Weisbach의 마찰수두 손실공식과 Schlichting 공식 사이의 적분관계 및 회귀분석을 통하여 개발하였다. 개발된 공식을 증명하기 위하여 매끄러운 관 자료가 사용되었으며 제안한 공식은 관측 자료와 비교하여 높은 정확성을 보여준다. 이 연구의 결과는 안정성 향상과 그리드 설계에 사용이 가능할 것으로 판단된다.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1998년도 춘계 학술발표회 논문집
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• pp.21-25
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• 1998

탈황설비 배관내 연소가스의 삼차원 유동장에 대한 전산해석을 수행하였다. 복잡한 형상으로 주어진 배관내의 유동장 특성을 관찰하고 압력손실을 계산하였다. 특히 안개깃의 설치유무에 따른 유동장 특성 변화 및 압력손실 감소효과를 집중적으로 고찰하였다. 안내깃의 설치에 따라 유량배분이 적절하게 되고 압력손실이 현저하게 줄어듬을 알 수 있었다. 배관에서의 압력손실을 계산하여 배관설계 및 송풍기 용량 산정의 적절성을 확인할 수 있었다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.489-494
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• 1997

A comparative transient analyses were performed for oxide and nitride cores or a large (3000 MWt), pool-type, liquid-metal-cooled reactor (LMR). The study was focused on three representative accident initiators with failure to scram : the unprotected loss-of-flow (ULOF), the unprotected transient overpower (UTOP), and the unprotected fast transient overpower (UFTOP). The margins to fuel melting and sodium boiling have been evaluated for these representative transients. The results show that there is an increase in safety margin with nitride core which maintains the physical dimensions of the oxide core.

• 한국유체기계학회 논문집
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• 제19권1호
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• pp.5-10
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• 2016

As a key component of a Francis turbine facility, the runner performance plays a vital role in the performance of the turbine. It is effective and successful to design a Francis turbine runner blade with good performance by one dimensional hydraulic design method. On the basis of one dimensional hydraulic analysis, there are a lot of parameters of the internal flow passage shapes determined by experience. Among those parameters, the effect of port area of blade on the performance of a Francis turbine is investigated in this study. A given Francis turbine model was selected for investigating the port area of blade on the performance. The result shows that the effect of port area of runner blade on the outflow angle from runner passage on the performance is quite significant. A correct exit flow angle reduces the energy loss at draft tube, which has the best efficiency of the turbine model.

• 대한기계학회논문집B
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• 제20권7호
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• pp.2315-2325
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• 1996

A compression wave is attenuated or distorted as it propagates in a tube. The present study investigated the propagation characteristics of the compression waves which are generated by a train in a high-speed railway tunnel. A Total Variation Diminishing (TVD) difference scheme was applied to one-dimensional, unsteady viscous compressible flow. The numerical calculation involved the effects of wall friction, heat transfer and energy loss due to the friction heat in the boundary layer behind the propagating compression wave, and compared with the measurement results of a shock tube and a real tunnel. The present results show that attenuation of the compression wave in turbulent boundary layer is stronger than in laminar boundary layer, but nonlinear effect of the compression wave is greater in the laminar boundary layer. The energy loss due to the frictional heat had not influence on attenuation and distortion of the propagating compression waves.

• Journal of Advanced Research in Ocean Engineering
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• 제1권2호
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• pp.73-84
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• 2015

The turbine is one of the most important components in the tidal current power device which can convert current flow to rotational energy. Generally, a tidal turbine has two or three blades that are subjected to hydrodynamic loads. The blades are continuously deformed by various incoming flow velocities. Depending on the velocities, blade size, and material, the deformation rates would be different that could affect the power production rate as well as turbine performance. Surely deformed blades would decrease the performance of the turbine. However, most studies of turbine performance have been carried out without considerations on the blade deformation. The power estimation and analysis should consider the deformed blade shape for accurate output power. This paper describes a fluid-structure interaction (FSI) analysis conducted using computational fluid dynamics (CFD) and the finite element method (FEM) to estimate practical turbine performance. The loss of turbine efficiency was calculated for a deformed blade that decreased by 2.2% with maximum deformation of 216mm at the blade tip. As a result of the study, principal causes of power loss induced by blade deformation were analysed and summarised in this paper.

• 한국태양에너지학회 논문집
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• 제39권6호
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• pp.27-40
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• 2019

Kitchen hoods are limited in discharging all contaminants produced during cooking. Contaminants that have not been discharged can rise to the upper part of the kitchen and become stacked. To solve this problem, there is a way to increase the air volume of the kitchen hood, but there are limits, so a new system is required. This study proposes the Duct System (IADK : Inducing Airflow Duct system for Kitchen hood )through 3D printers and experiments. To do this, the pressure is measured to verify the three levels of air volume provided by the kitchen hood. To check the degree of loss of flow in the existing kitchen hood system, install flexible ducts alone to measure the pressure. Change the internal diameter and type of connection of the IADK and measure the pressure. The air pressure, static pressure difference, and loss factor are calculated and analyzed using the pressure measured through the experiment.