• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.107-110
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• 2009

A basic design for a Technical Development Model (TDM) of liquid oxygen lines from the turbopump exit to the oxidizer valves of the combustion chamber and the gas generator was conducted to develop a turbopump-fed liquid rocket engine. The TDM is composed of straight lines, elbows, bellows, a branch, an orifice, flanges and a heat insulator. Materials were determined by consideration of operation conditions, weight constraint and manufacturing procedures. The size and the location of each component were determined by flow analysis of the required flowrate and the pressure loss. Basic designs of the components were conducted by consideration of the operating temperature and the maximum expectation operating pressure. The safety factors were evaluated by structural analysis of design of each component.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.15-24
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• 1986

Pressure trasients must deal with safety problem of system. For identification of physical situation that can and method of limiting surges are essential consideration in sucessful design. The finite difference equation by method of characteristics are derived from the governing equation of unsteady flow in a pipe, and solved by using boundary condition derived. A computer program which can simulate general hydraulic system is developed by using finite difference equations and boundary conditions derived. The sumulated resulted by developed computer program are in fair agreement with experiment result.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.23-29
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• 2006

In an annular injection supersonic ejector, the supersonic primary flow is injected along the side wall, therefore a funnel-shaped shock wave is generated by the contraction angle of the mixing chamber. In the present study, we developed a simple funnel shock wave model using 2-D wedge and conical shock wave relations. In result, the secondary flow pressure can be predicted more accurately than using a simple 2-D wedge shock wave model. Through the same analysis, the compression ratio and the adiabatic efficiency according to the entrainment ratio were calculated.

• Journal of the Korean Solar Energy Society
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• v.31 no.5
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• pp.67-76
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• 2011

생활공간 냉난방용 열펌프의 성능향상을 위해 R22의 대체 냉매로서 새로운 혼합냉매R22/R23/R152a(RM-1)을 개발하고 U. S. A.의 NIST사의 REFPRO Pprogram을 이용해 이 혼합냉매의 P-h diagram을 구성하여 실용화에 이용할 수 있도록 하였다. 본 연구는 실험을 통해 R22와 RM-1의 열펌프 성능효과를 분석하였다. 입 출구 물의 온도와 제2의 전열매체로서 물의 질량유량, 압축기의 소요 에너지 그리고 열펌프의 기타 열적 특성을 다양한 조건하에서 측정하였다. 이 실험 데이터를 통해 공기-물 열펌프 시스템에서의 RM-1과 R22의 성능계수(COP)를 비교하였다. 이를 통해, 혼합냉매 RM-1을 사용하는 열펌프 시스템은 외기온 $-17^{\circ}C$에서도 2.2의 성능계수로 작동하는 결과를 본 연구에서 보여주었다.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.1
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• pp.13-21
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• 2000

The advantages of the SITVC (Secondary Injection for Thrust Vector Control) technique over mechanical thrust vectoring systems include a reduction in both the nozzle weight and complexity due to the elimination of the mechanical actuators that are used in conventional vectoring. The optimal operating conditions of SITVC were investigated using in-house developed compressible flow analysis codes. Numerical experiments were used to examine the impact of the thrust vector direction with a variety of injection positions, mass flow rates, and injection angles on the two-dimensional expansion cone of a supersonic nozzle. The computational results showed that the optimal position of the secondary injection, with the maximum deviation angle and side thrust, was where the oblique shock generated by the secondary injection reached the end of the nozzle exit.

• Journal of Energy Engineering
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• v.10 no.1
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• pp.24-32
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• 2001

본 축열탱크 열전달에 관한 실험적 연구는 국내에서 개발하고 있는 태양열 온수기용으로 현재 널리 이용되고 있는 탱크-코일 방식의 문제점을 해결하면서 열전달 효율이 높은 2중 축열탱크를 개발하기 위한 것이다. 2중 축열탱크의 용량은 100리터로서 수평 및 수직형으로 설치하여 실험이 가능하도록 설계.제작하였고 탱크내부의 온도는 길이방향 및 반지름 방향으로 각각 등간격으로 설치하여 측정하였고 집열매체의 입.출구온도를 동시에 측정하였다. 실험결과는 (1) 축열탱크의 형태에 관계없이 축열탱크와 열교환을 하는 열매체의 유량이 증가할수록 열전달량은 증가한다. (2) 축열탱크의 형태에 따른 탱크내부 물의 온도 상승속도는 수직형(b)인 경우가 가장 크고, 그 다음 수직형(a), 수평형의 순으로 나타났다. 따라서 이중탱크형의 축열탱크는 수평형 보다 수직형이 동일한 용량의 축열매체 온도를 신속히 상승시킬 수 있다. 아울러 열성층화에 의하여 고온의 축열매체를 이용할 경우 수직형 축열탱크가 더욱 우수한 결과를 나타낸다. (3) 축열탱크 열전달계수(UA) 값은 ( $T_{in}$ - $T_{out}$)/$\Delta$ $T_{m}$ 의 크기에 좌우되며, 열전달계수를 설치방법에 따라 비교하면 수직형(b)>수직형(a)>수평형의 순서로 나타났다.다.

• Journal of Drive and Control
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• v.19 no.1
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• pp.62-68
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• 2022

Considering the characteristics of industrial machines that lack vehicle-induced wind, forced convection by a cooling fan is mostly required. Therefore, numerical analysis of an engine room is usually performed to examine the cooling performance in the room. However, most engine rooms consist of a number of parts and components at specific positions, leading to high costs for numerical modeling and simulation. In this paper, a new methodology for three-dimensional computer-assisted design simplification was proposed, especially for the pile of components and parts at the engine room outlet. A porous media model and regression analysis were used to derive a meta-model for imitating the flow rate reduction at the outlet by the pile. The results showed that the fitted model was reasonable considering the coefficient of determination. The final numerical model of the engine room was then used to simulate the velocity distribution by changing the mass flow rate at the outlet. The results showed that both velocity distributions were significantly changed in each case and the meta-model was valid in imitating the flow rate reduction by some piles of components and parts.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.92-92
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• 2023

본 연구에서는 대한민국 도시 유역에 대하여 딥러닝 네트워크 기반의 분산형 수문 모형을 개발하였다. 개발된 모형은 완전연결계층(Fully Connected Layer)으로 연결된 여러 개의 장단기 메모리(LSTM-Long Short-Term Memory) 은닉 유닛(Hidden Unit)으로 구성되었다. 개발된 모형을 사용하여 연구 지역인 중랑천 유역을 분석하기 위해 1km² 해상도의 239개 모델 격자 셀에서 10분 단위 레이더-지상 합성 강수량과 10분 단위 기온의 시계열을 입력으로 사용하여 10분 단위 하도 유량을 모의하였다. 모형은 보정과(2013~2016년)과 검증 기간(2017~2019년)에 대한 NSE 계수는각각 0.99와 0.67로 높은 정확도를 보였다. 본 연구는 모형을 추가적으로 심층 분석하여 다음과 같은 결론을 도출하였다: (1) 모형을 기반으로 생성된 유출-강수 비율 지도는 토지 피복 데이터에서 얻은 연구 지역의 불투수율 지도와 유사하며, 이는 모형이 수문학에 대한 선험적 정보에 의존하지 않고 입력 및 출력 데이터만으로 강우-유출 분할과정을 성공적으로 학습하였음을 의미한다. (2) 모형은 연속 수문 모형의 필수 전제 조건인 토양 수분 의존 유출 프로세스를 성공적으로 재현하였다; (3) 각 LSTM 은닉 유닛은 강수 자극에 대한 시간적 민감도가 다르며, 응답이 빠른 LSTM 은닉 유닛은 유역 출구 근처에서 더 큰 출력 가중치 계수를 가졌는데, 이는 모형이 강수 입력에 대한 직접 유출과 지하수가 주도하는 기저 흐름과 같이 응답 시간의 차이가 뚜렷한 수문순환의 구성 요소를 별도로 고려하는 메커니즘을 가지고 있음을 의미한다.

• Fire Science and Engineering
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• v.27 no.6
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• pp.1-7
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• 2013

In this study, the effects of various disk shapes of hydrant on the pressure drop are experimentally and numerically analyzed. The test methods for measuring pressure drop of hydrant are comply with standard of Underwriters Laboratory (UL). The hydrant as used in this study has one inlet, diameter 150 mm, and three outlet, 114.3 mm diameter for one outlet and 63.5 mm diameter for the others. The pressure of the hydrant are measured in the range 760 L/min~2,270 L/min for 63.5 mm outlet and 3,030 L/min~6,060 L/min for 114.3 mm outlet. Also, the numerical results of pressure drop are compared with the experiments to verify the accuracy and to analyze the of various valve shape of hydrant on the pressure drop. The engineering parameters, flow coefficients, are reduced from 181.57 to 136.35 ($L/min/kPa^{0.5}$) with inclined angle of disk from $0^{\circ}$ to $45^{\circ}$. These results are able to practical use for design hydrant to minimize pressure drop.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.400-406
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• 2017

The model used in this study was reversed to analyze the cause of excessive damage that occurred inside the rotating system and pipe system of a centrifugal-type seawater pump on a ship. For this purpose, internal flow analysis on a cooling seawater pump was performed using CFD. As a result, the shape and boundary conditions of the target pump were set by reverse engineering, and pump efficiency at a design operating point of $125m^3/h$ was calculated as 85.3 % with a head of 32.0 m. The maximum efficiency point of the target pump was estimated to be 86.2 % at $150m^3/h$, but this differed from the actual operating point. At $112.5m^3/h$, which was the lowest flow point, flow was unstable due to the characteristics of the low flow point and analysis convergence was not good. The purpose of this study was to clarify the cause of ongoing cavitation in seawater pumps and piping systems in operation. Future research will be needed to clarify causes for pipe systems in the future by performing calculations for the total piping system of an inlet and outlet, in addition to measuring the flow rate of each branch pipe.