• 대한설비공학회지:설비저널
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• 제17권6호
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• pp.696-707
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• 1988

This study simulates a typical solar system using the transient simulation program TRNSYS, and calculates the maximum cooling load of the model room of $50m^2$. In this study, energy rate control method is used in calculating a maximum cooling load. On the ground of the maximum cooling load of the model room, the variables that have an effect on the solar collection performance of the solar system are made a selection. Also in this study the trend of the solar collection performance is shown as the variables change. The results show that the variables which have an effect on the collection performance are collector area, collector mass flow rate, collector slope and the volume of storage tank, and the optimal value of Ac/Vt is not constant but varies as the collector area and the collector mass flow rate. Also the results show that for cooling system the optimal value of the collector slope is latitude minus $15^{\circ}$ during the seasonal operations, and twenty percent of the maximum cooling load is saved with the aid of the solar energy.

• 대한기계학회논문집B
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• 제37권11호
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• pp.1015-1022
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• 2013

본 연구에서는 현재 개발중인 200kW 급 마이크로 가스터빈의 운전 특성을 모사하였다. 세부적인 성능 데이터를 이용하여 부분부하 제어방식(터빈 입구온도 제어방식(constant TIT control)과 터빈 출구온도 제어방식(constant TET control))과 외기온도에 따른 성능 및 작동특성을 분석하였다. 넓은 운전 범위에 대하여 압축기 서지마진과 터빈 입출구 온도 같은 작동 파라미터의 민감도를 단위 연료량 변화에 따라 예측하였다. 정상상태 계산으로 부분부하 변동 시 최대서지마진의 감소에 대한 정보를 민감도 분석을 통해 알 수 있다.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3030-3034
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• 2015

새로운 엔진과 차량을 개발하여 엔진을 차량에 탑재할 때, 중요하게 고려해야 할 사항 중의 하나는 냉각 성능이다. 만약 냉각 성능이 열악하다면 엔진은 과열되어 파손되게 된다. 그러나 자동차회사에서 일반적으로 엔진은 차량보다 훨씬 빠른 시기에 개발이 진행되게 되어 엔진을 차량에 탑재한 조건에서 냉각 성능을 시험할 수 없다. 본 연구에서는 몇 가지 시험과 계산 결과를 이용하여 엔진의 냉각 성능을 추정하였다. 첫 번째로 엔진의 열정산 시험이 진행되었다. 두 번째로 냉각수 유동 시험이 진행되었다. 이 시험에서 라디에이터로 유입되는 유량을 구할 수 있다. 그리고 차량의 냉각 시험 성능 조건으로부터 차량의 부하와 속도를 구하고, 이로부터 엔진의 토크와 rpm이 계산되었다. 그리고 이러한 결과를 비교하여 엔진의 냉각 성능이 추정되었다.

• Wind and Structures
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• 제5권2_3_4호
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• pp.329-336
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• 2002

The along-wind response of a surface-mounted elastic fence under the action of wind was investigated numerically. In the computations, two sets of equations, one for the simulation of the unsteady turbulent flow and the other for the calculation of the dynamic motion of the fence, were solved alternatively. The resulting time-series tip response of the fence as well as the flow fields were analyzed to examine the dynamic behaviors of the two. Results show that the flow is unsteady and is dominated by two frequencies: one relates to the shear layer vortices and the other one is subject to vortex shedding. The resulting unsteady wind load causes the fence to vibrate. The tip deflection of the fence is periodic and is symmetric to an equilibrium position, corresponding to the average load. Although the along-wind aerodynamic effect is not significant, the fluctuating quantities of the tip deflection, velocity and acceleration are enhanced as the fundamental frequency of the fence is near the vortex or shedding frequency of the flow due to the occurrence of resonance. In addition, when the fence is relatively soft, higher mode response can be excited, leading to significant increases of the variations of the tip velocity and acceleration.

• KIEAE Journal
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• 제14권3호
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• pp.65-70
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• 2014

The thermal environment in a small city rapidly deteriorates due to the urbanization and overpopulation. It is important to understand and predict the thermal environment in a city area. The thermal environment is highly affected by the solar radiation and temperature distributions changing over time periodically. To predict the thermal environment precisely, the solar radiation calculation including radiation strength, incidence angle, and thermal radiation between building surface and ground should be considered. In this study, the computational domain includes various artificial structures such as building, ground, asphalt, brick and grass. To consider the solar radiation, the unsteady state numerical calculation is performed from sun rise to mid-day (2:00pm). The numerical methods consist of solar load and one dimensional heat conduction through the boundaries to reduce the computational load and improve the flexibility of the calculation.

• 한국농공학회논문집
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• 제63권5호
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• pp.73-81
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• 2021

The objective of this study was to analyze the waste nutrient generation loads from hydroponics for three major crops in Gyeongsangnam-do. Study hydroponic farms were selected for the three major crops such as paprika, strawberry, tomato based on the agricultural statistics data and field investigation. The flow amount and water quality for inflow and outflow of study hydroponic farms were monitored and analyzed on a monthly basis. Monitored samples were analyzed in terms of DO, BOD, T-N, T-P, SS, and EC. The generated load of BOD, T-N, and T-P were calculated from the monitored flow and water quality. The monitoring results showed that the drainage ratio for the circular hydroponic farm was lower than the non-circular hydroponic farm because the outflow from the circular hydroponics were much lower than that from the non-circular. The generated load calculation results showed that the BOD tended to have a smaller value than the TMDLs guideline for land, while T-N and T-P showed higher value than that from the TMDLs guideline. In order to effectively manage the pollutant load discharged from the hydroponics farming complex, it is necessary to manage the non-circulating hydroponics farm. To improve water quality, it is necessary to gradually expand the circulating hydroponics farm through policy and economic support.

• Nuclear Engineering and Technology
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• 제20권1호
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• pp.1-8
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• 1988

상업용 발전소의 가동시, 출력 변화에 의해 1차 계통 보론 농도의 변화가 요구되었을 때 CVCS보충 시스템에서의 보충 유량이 연속 방정식과 질량 평형 방정식을 이용하여 측정된다. 이를 위하여, 1차 계통, 가압기, 그리고 volume control tank가 각각 질량과 보론 농도를 가진 control volume으로 그리고 1차측과 가압기, CVCS를 연결하는 파이프들이 시간 지연 요소로 모델화 되었다. 14-2-6-2 (출력변화 100-50-100) 부하 추종운전의 경우(7호기 EOL에서)를 이 모델을 이용하여 계산하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권4호
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• pp.699-707
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• 2015

The ice-resistance estimation technique for icebreaking ships had been studied intensively over recent years to meet the needs of designing Arctic vessels. Before testing in the ice model basin, the estimation of a ship's ice resistance with high reliability is very important to decide the delivered power necessary for level ice operation. The main idea of previous studies came from several empirical formulas, such as Poznyak and Ionov (1981), Enkvist (1972) and Shimansky (1938) methods, in which ice resistance components such as icebreaking, buoyancy and clearing resistances were represented by the integral equations along the Design Load Water Line (DLWL). The current study proposes a few modified methods not only considering the DLWL shape, but also the hull shape under the DLWL. In the proposed methodology, the DLWL shape for icebreaking resistance and the hull shape under the DLWL for buoyancy and clearing resistances can be directly considered in the calculation. Especially, when calculating clearing resistance, the flow pattern of ice particles under the DLWL of ship is assumed to be in accordance with the ice flow observed during ice model testing. This paper also deals with application examples for a few ship designs and its ice model testing programs at the AARC ice model basin. From the comparison of results of the model test and the estimation, the reliability of this estimation technique has been discussed.

• Structural Engineering and Mechanics
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• 제64권1호
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• pp.23-31
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• 2017

In the study, dynamic behavior of laminated orthotropic beams on elastic foundation is investigated. Consistent model presented here combines the finite element solution of the system with SAP2000 software and the calculation of soil parameters with MATLAB software using Modified Vlasov Model type elastic foundation. For this purpose, a computing tool is coded in MATLAB which employs Open Application Programming Interface (OAPI) feature of SAP2000 to provide two-way data flow during execution. Firstly, an example is taken from the literature to demonstrate the accuracy of the consistent FEM-Vlasov Model. Subsequently, the effects of boundary conditions, subsoil depth, elasticity modulus of subsoil, slenderness ratio, velocity of moving load and lamination scheme on the behavior of laminated orthotropic beams on elastic foundation are investigated on a new numerical example. It can be concluded that it is really convenient to use OAPI feature of SAP2000 to model this complex behavior of laminated orthotropic beams on elastic foundation under moving load.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.7-9
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• 2001

Many developing countries has been voltage unstable and the inter- change capability in Korea is limited by voltage instability. In analyzing voltage stability, load model has been considered as constant power, but actual loads vary as voltage changes. In order to incorporating voltage-dependent load model. we need the low-side of P-V curve that can not be obtained by general load flow algorithm. This paper proposes a modified GCF algorithm to obtain a full low-side of P-V curve and a accurate voltage assessment index considering load model. 5-bus sample system and 19-bus real power system are applied to simulate the proposed GCF. Also. the effect of reactive power compensation is illustrated in same systems.