• 한국지열·수열에너지학회논문집
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• 제6권1호
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• pp.9-16
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• 2010

The aim of this study is to verify the performance of water-to-air multi-heat pump system with a vertical U-tube GLHX(U-tube system) and a double tube GLHX(double tube system), which were installed in a school building located in Asan. For analyzing the performance of the GSHP system, we monitored various operating da~ including the water temperature of inlet and outlet of the ground heat exchanger, mass flow rate, and power consumption. Daily average COP of the single U-tube system and the double tube system were 4.5 and 4.2 at cooling mode and were 3.5 and 3.8 at heating mode. As a result, We know that performance of water-to-air multi-heat pump unit is reliable at actual condition operated in a part load conditions for all day.

• 한국전산구조공학회논문집
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• 제16권1호
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• pp.33-42
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• 2003

본 논문에서는 2차원 사각탱크내 비압축성, 비점성, 비회전 유동에 대한 비선형 슬로실 해석을 다룬다. 유체영역의 지배방정식으로 포텐셜 이론에 기반을 둔 라플라스 방정식을 사용한다. 대변형의 슬로싱 거동을 표현하기 위하여 베르누이 방정식으로부터 유도된 운동 및 동역학적 자유표면 경계조건을 적용한다. 이러한 비선형 슬로싱 문제는 9결점 요소를 사용한 유한요소법에 의하여 해석되어 진다. 경계조건에 대한 시간적분과 정확한 속도계산을 위하여 각각 예측자-수정자 기법 및 최소자승법을 도입하였다. 또한, 자유표면 추적에서 야기되는 안정성 문제는 시간변동에 대한 자유표면 위치를 직접 계산함으로써 확보할 수 있었다. 외부 조화가진에 대한 본 논문의 결과는 선형이론해 또는 참고문헌의 결과와 비교하여 매우 정확하고 안정적이었다. 프로그램 검증 후, 유체높이와 가진크기에 대한 슬로싱 응답특성을 분석하였다.

• Advanced Composite Materials
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• 제17권1호
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• pp.57-73
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• 2008

The present paper focuses on experimental verification of the ply-by-ply basis inelastic analysis of multidirectional laminates. First of all, rate dependence of the tensile behavior of balanced symmetric cross-ply T800H/epoxy laminates with a $[0/90]_{3S}$ lay-up under off-axis loading conditions at $100^{\circ}C$ is examined. Uniaxial tension tests are performed on plain coupon specimens with various fiber orientations $[{\theta}/(90-{\theta})]_{3S}$ ($\theta$ = 0, 5, 15, 45 and $90^{\circ}C$) at two different strain rates (1.0 and 0.01%/min). The off-axis stress.strain curves exhibit marked nonlinearity for all the off-axis fiber orientations except for the on-axis fiber orientations $\theta$ = 0 and $90^{\circ}$, regardless of the strain rates. Strain rate has significant influences not only on the off-axis flow stress in the regime of nonlinear response but also on the apparent off-axis elastic modulus in the regime of initial linear response. A macromechanical constitutive model based on a ply viscoplasticity model and the classical laminated plate theory is applied to predictions of the rate-dependent off-axis nonlinear behavior of the cross-ply CFRP laminate. The material constants involved by the ply viscoplasticity model are identified on the basis of the experimental results on the unidirectional laminate of the same carbon/epoxy system. It is demonstrated that good agreements between the predicted and observed results are obtained by taking account of the fiber rotation induced by deformation as well as the rate dependence of the initial Young's moduli.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.21-26
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• 2008

Recently, small and medium-sized buildings have employed a multi-heat pump. The major benefits of the multi-heat pump over a conventional system are that it is easier system to maintain along with a diversification of facility use, and high comfortability. The performance of multi-heat pump systems can be enhanced by using geothermal energy instead of air source energy. This paper describes the multi-heat pumps applied in an ground source heat pump system for an actual building. The performance of a ground source multi-heat pump installed in the field was investigated in cooling mode. The maximum COP of the systems with single U-tube and double tube ground loop heat exchangers were 6.6 and 6.0, respectively. It is suggested that the new algorithms to control the flow rate of secondary fluid for ground loop heat exchanger have to be developed in order to enhance the performance of the system.

• Journal of Ship and Ocean Technology
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• 제12권1호
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• pp.16-27
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• 2008

The interaction between advancing ships and the waves generated by them plays important roles in wave resistances and ship motions. Wave breaking phenomena near the ship bow at different speeds are investigated both numerically and experimentally. Numerical simulations of free surface profiles near the fore bodies of ships are performed and visualized to grasp the general trend or the mechanism of wave breaking phenomena from moderate waves rather than concentrating on local chaotic irregularities as ship speeds increase. Navier-Stokes equations are differentiated based on the finite difference method. The Marker and Cell (MAC) Method and Marker-Density Method are employed, and they are compared for the description of free surface conditions associated with the governing equations. Extra effort has been directed toward the realization of extremely complex free surface conditions at wave breaking. For this purpose, the air-water interface is treated with marker density, which is used for two layer flows of fluids with different properties. Adaptation schemes and refinement of the numerical grid system are also used at local complex flows to improve the accuracy of the solutions. In addition to numerical simulations, various model tests are performed in a ship model towing tank. The results are compared with numerical calculations for verification and for realizing better, more efficient research performance. It is expected that the present research results regarding wave breaking and the geometry of the fore body of ship will facilitate better hull form design productivity at the preliminary ship design stage, especially in the case of small and fast ship design. Also, the obtained knowledge on the impact due to the interaction of breaking waves and an advancing hull surface is expected to be applicable to investigation of the ship bow slamming problem as a specific application.

• 한국ITS학회 논문지
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• 제13권2호
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• pp.1-11
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• 2014

본 논문의 목적은 DSRC 기반 통행속도 이력데이터를 활용하여 IC-IC 구간 단위의 통행패턴을 도출하는 것이며, 이를 통해 방대한 이력정보 데이터의 활용도를 높이고, 단순하지만 정확성 높은 방법으로 도로의 통행패턴을 용이하게 파악할 수 있게 하는 것이다. 통행패턴 분류는 의사결정나무 기법을 적용하였고, 월 시간대 구간 단위로 분리된 통행패턴을 생성하여 시 공간이 변화되어도 이에 대응 가능하도록 하였다. 경부고속도로 서울TG~안성IC 구간을 대상으로 의사결정나무 기법을 적용한 결과, 요일 기준으로 (월)(화 수 목)(금)(토)(일) 5개 그룹으로 고정 통행패턴이 분류되었다. 분류 결과를 영동, 중부, 중부내륙 고속도로의 9개 구간에 적용하여 통계적 검증을 수행한 결과 약 93%의 적합도를 갖는 것으로 나타났다. 의사결정나무를 통한 통행패턴 오차를 개선하기 위하여 4개의 추가변수를 도입한 결과, "직전월의 소통상황"을 설명변수로 추가할 경우 통행속도 분산이 약 50% 감소함을 확인하였고, 실제 상황에 적용할 경우 소통 원활 시의 오차가 약 4% 감소되었다.

• Nuclear Engineering and Technology
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• 제36권6호
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• pp.528-539
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• 2004

It is essential in commercial reactors that the safety limits imposed on the fuel pellets and fuel clad barriers, such as the linear power density (LPD) and the departure from nucleate boiling ratio (DNBR), are not violated during reactor operations. In order to accurately monitor the safety limits of current reactor states, a detailed three-dimensional (3D) core power distribution should be estimated from the in-core detector signals. In this paper, we propose a calculation methodology for detailed 3D core power distribution, using in-core detector signals and core monitoring constants such as the 3D Coupling Coefficients (3DCC), node power fraction, and pin-to-node factors. Also, the calculation method for several core safety parameters is introduced. The core monitoring constants for the real core state are promptly provided by the core design code and on-line MASTER (Multi-purpose Analyzer for Static and Transient Effects of Reactors), coupled with the core monitoring program. through the plant computer, core state variables, which include reactor thermal power, control rod bank position, boron concentration, inlet moderator temperature, and flow rate, are supplied as input data for MASTER. MASTER performs the core calculation based on the neutron balance equation and generates several core monitoring constants corresponding to the real core state in addition to the expected core power distribution. The accuracy of the developed method is verified through a comparison with the current CECOR method. Because in all the verification calculation cases the proposed method shows a more conservative value than the best estimated value and a less conservative one than the current CECOR and COLSS methods, it is also confirmed that this method secures a greater operating margin through the simulation of the YGN-3 Cycle-1 core from the viewpoint of the power peaking factor for the LPD and the pseudo hot pin axial power distribution for the DNBR calculation.

• 한국시뮬레이션학회논문지
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• 제15권2호
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• pp.1-12
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• 2006

지능형 시스템에 대한 요구가 지속적으로 증가하면서, 최근에는 인공지능과 시뮬레이션 기술을 연동하기 위한 다양한 접근이 이루어지고 있다. 본 논문의 기반이 되는 RG-DEVS는 이산 사건 시뮬레이션 모델링 방법론인 DEVS에 인공지능의 계획(planning) 기술을 반영함으로써 동적으로 시뮬레이션 모델이 정의될 수 있는 인공지능과 시뮬레이션의 연동 기술이다. 그러나, 오늘날 많은 문제 해결 시스템들에 반영되고 있는 계층성(hierarchy)이 계획에 반영되어 있지 않다. 계층성은 탐색 공간을 작게 하여 계획의 계산 비용을 줄일 수 있을 뿐 아니라, 모델링 대상 시스템의 계층적 작업 흐름을 반영하기에도 유용하다. 본 논문은 RG-DEVS에 계층적 계획 능력을 추가하여 확장한 모델링 방법론인 HRG-DEVS출 제안하고, 이를 검증하기 위하여 고전적인 계획 문제로 알려진 계층적인 블록 쌓기 문제인 ABSTRIPS에 적용하였다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.205-210
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• 2009

Generally, the building's windows and ventilation for the purpose of mining and the vista and windows by emotional engineering design area is a growing trend. According to the flow of energy is lost from the building, will be achieved through the walls and roof and windows. Among these, the window through the loss of about 45% of the entire building is big enough to rate. In addition, the building regulation U-value Limitation of window is $3.3W/m^2$ K in southern regions, while U-value Limitation of wall is $0.35{\sim}0.58W/m^2$ K. It means that the energy loss through windows is six times more than it through wall. Therefore, the purpose of this study is to evaluate the environmental performance of the super window system by verification experiment. The results of this study are as follows; 1)Thermal performance of insulated Super Window measured as $1.44W/m^2$ $^{\circ}C$ 2)Required energy for heating was cut down about 5.3% from 266.99 $MJ/m^2$ yr to 252.85 $MJ/m^2$ yr 3)Super Window's reduction rates increased 4.1% from 31.48% to 35.58% when it is compared to normal windows. 4)Building energy efficiency rating elevated from 2nd rating to 1st rating.

• 물과 미래
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• 제29권3호
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• pp.163-176
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• 1996

균일조도관이 경사지어 설치되어 있을 때, 적정량의 유체를 유송하기 위하여 요구되는 펌프의 동력은 양해법으로 바로 산정할 수 있다. 그러나 펌프의 동력이 기지값으로 주어져 있고 관내 유출률이나 관경을 구하고자 할 때 기존 방법은 상당한 반복과정을 거쳐야 된다. 이러한 경우 유동훈(1995b)은 펌프가 작동치 않는 자연경사관이나 수평관에 펌프만 작동할 때의 균일조도관에 대하여 양해법 산정식을 개발한 바 있다. 본 연구는 그의 연구결과에 기초하여 균일조도 경사관에 펌프가 동시에 작동할 때 반복 시산과정을 거치지 않고 관내 유출률이나 관경을 양해법으로 바로 산정하는 수식을 개발하여 제시하였다. 양해법 산정식의 선택에 있어 관로흐름의 수리특성을 다섯가지로 구분하여 각 수리 특성구간의 경계조건식도 양해법으로 도출하였다. 또한 개발된 양해법 근사식을 간단한 설계예에 적용하여 계산의 효율성과 정확성을 확인하였다.