• Proceedings of the KAIS Fall Conference
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• 2010.05a
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• pp.67-70
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• 2010

국가차원의 신 재생에너지 활성화 방안에 따라 태양광, 풍력발전 등의 대규모 분산전원 단지의 도입이 이루어지고 있으며, 현재 배전계통의 전압조정 방법은 배전용 변전소의 부하시 탭 절환기(Under Load Tap Changer, 이하 ULTC)와 배전선로의 선로전압조정장치(Step Voltage Regulator, 이하 SVR)로 수용가에 규정전압(220${\pm}$6%)을 만족시키는 전압을 공급한다. 하지만 대규모의 태양광, 풍력 등의 분산 전원이 배전계통에 도입되는 경우, 전력품질[과전압/저전압]의 문제가 발생된다. 본 논문에서는 부하율에 따라 변화된 LDC 정정치를 적용 및 시뮬레이션을 통한 수용가 직하 및 말단의 규정전압(220${\pm}$6%) 즉 207V이하의 저전압, 233V이상의 과전압 여부를 검증함으로써 전력품질을 유지 할 수 있는 태양광전원이 연계된 배전계통의 최적전압운용 알고리즘을 개발하였다.

• Solar Energy
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• v.10 no.2
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• pp.10-17
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• 1990

Short-term tests were conducted on a house at KIER, Daejon for its thermal performance evaluation. The test procedure and data analysis were made according to the PSTAR method. Each test period was 3 days during which the building was unoccupied. The data measured with 8 channels were used to renormalize an audit based simulation model of the house. The following are the key parameters obtained in the present analysis: 1) the building loss coefficient(skin conductance plus infiltration conductance during coheating period); 2) the effective building heat capacity; and 3) the effective solar gain. An estimation of total heat required to maintain a standard level of comfort during a typical winter season is also calculated on the basis of the renormalized simulation model and typical long term weather data.

• Tunnel and Underground Space
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• v.19 no.6
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• pp.507-516
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• 2009

In cases of high-level radioactive waste repositories, heat load is apparent by radioactive waste decay. The safety of a waste repository would be influenced by changing circumstances caused by heat transfer through rock. Thus, a ventilation system is necessary to secure the waste repository. The first priority for building an appropriate ventilation system is completing a computer simulation research with thermal rock properties and a heat transfer coefficient. In this study, the heat transfer coefficient in KURT was calculated using the measurement of inner circumstance factors that include dry bulb and wet bulb temperature, rock surface temperature, and barometric pressure. The heater that is 2 m in length and 5 kw in capacity heats the inside of rock in the research module by $90^{\circ}C$. As a result of determining the heat transfer coefficient in the heating section, the changes of heat transfer coefficient were found to be a maximum of 7.9%. The average heat transfer coefficient is approximately 4.533 w/$m^2{\cdot}K$.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.170-170
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• 2017

기후변화 따른 스마트팜 돈사 외부 환경의 변화에 대응하고, 사육 환경을 능동적으로 개선하기 위한 연구가 수행 중이다. 돈사 내 열전달 요소 간 상호 역학성 분석을 위해서 고려해야할 사항은 입기구, 보온 등, 열풍기, 단열제, 위치, 방향, 돈사의 연평균 온도, 습도, 연중 일사량, 가축의 열복사 등 상호 복잡하게 연관되어 있는 물리량이다. 돈사 전체 열손실, 자연발생 에너지량, 강제발생 에너지량, 난방용량 등을 고려한 순간 열부하 산정을 위한 여러 방법 중 우선적으로 CFD(Computational Fluid Dynamics)를 이용하였다. 순간 열부하 산정을 위한 해석 도구 선정에 있어서 다양한 유체 및 기체 전산 유체역학 Solver(Fluent, Open-FOAM, Blender)를 고려하였다. 공간 Mech를 수행하기 위한 도구로는 공개 소프트웨어 인 FreeFem++ 3.51-4 (http://www.freefem.org)를 이용하였다. 이 과정에서 일부 기체 (암모니아)의 농도를 난수로 변화시키는 기법을 적용하여 가상적으로 돈사의 환경을 Pseudo 시뮬레이션 하였다. 결과적으로 Fluent에 비하여 OpenFOAM을 이용하여 얻은 열유동의 방향(속도)과 크기 백터가 상대적으로 크게 나타났다. Fluent가 시계열 상에서 혼합 기체 물리량 변화를 무시할 수 있는 안정되고 균일한 환경에 적합하기 때문인 것으로 판단되었다. Blender의 경우 Lattice Boltzmann methods 과 Smoothed-particle hydrodynamics 방법을 이용한 유체/입자 동력학 모델링을 제공함에 있어 시각적 효과를 강조하는 기능에 중점을 두었다. Fluent와 Blender에서 제공하는 해석 연산 모듈의 정확성 검증을 위해선 공간 분해능을 높인 정밀 계측 시스템을 이용하여 검증할 필요가 있다. Open-FOAM를 이용한 열부하 분석 수행이 상대적으로 높은 절대값을 보이는 특성은 열부하 제어 시스템의 Overshoot를 유발할 가능성이 있으므로 이에 대한 해석 모델의 보정이 추가적으로 필요할 것이다. CFD의 한계인 시간 복잡도를 낮추고 상대적으로 높은 시계열 분해능을 확보할 경우 돈사 내 환기시스템에 맞는 소요 환기량 실시간 산정이 가능해지고 외부기상 및 돈사내부 복사열을 활용함과 동시에 돈군 순환에 상응하는 실시간 열부하 관리 시스템 도출이 가능할 것이다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2086-2091
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• 2013

One of the most important objects for the industrial ventilation is to protect worker's health from the harmful substances. Mainly in industrial ventilation, the harmful substances broken out through manufacturing process are to be quickly emitted outside. Recently the importance of the industrial ventilation increases with the recognition change of industrial ventilation from manufacturing focusing to human focusing. In this paper, the air flow simulation inside the coating room is performed. All the coating room and the ventilation system are modeled by SolidWorks program and air flow distribution and ventilation performance are analyzed by Flow simulation program. And the air flow directions and the air flow velocities inside the coating room are enhanced with the use of local ventilation.

• KIEAE Journal
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• v.15 no.2
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• pp.123-131
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• 2015

Purpose : Improvement of indoor thermal comfort and reduction of the energy consumption in building can be obtained by applying a double skin facade system. In order to achieve effectively this purpose, design team would have to perform easy and appropriate performance analysis for making better design decision during the design process. Method : This paper focus on the natural ventilation performance of a multi-story type double skin facade with main causes which are pressure difference according to the wind and temperature difference between indoor and outdoor (Buoyancy Effect). Using this main causes, the natural ventilation ratio of wind effect-to-buoyancy effect in cavity of multi-story type double skin facade were analyzed through the performance analysis results of CFD (Computational Fluid Dynamics) simulation. Result : When the wind velocity was 2m/s, the ventilation rate in the cavity was highest. If wind velocity was slower than 2m/s wind velocity, buoyancy effect has more influence on the ventilation rate in the cavity, and if wind velocity was faster than 2m/s wind velocity, wind effect has more influence on the ventilation rate in the cavity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.11
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• pp.421-427
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• 2016

The indoor temperature of a building increases during the day due to solar radiation. This behavior is significant in school buildings that are finished with high thermal capacity materials. Moreover, in school buildings, windows cannot be opened until the class has finished owing to the security policy of schools. Consequently, classrooms maintain a high temperature throughout the morning. It is thus important to remove the indoor heat before the commencement of classes in order to reduce the cooling energy needed. The Energy Recovery Ventilator (ERV) system is currently being installed in school buildings for ventilating the classrooms. Night-purge control using ERV can be a good strategy to cool the classroom in advance of the operation of the cooling system. However, the optimal operation method of the ERV for night-purge control has not yet been reported. In this study, the effect of night-purge control with ERV in school buildings is analyzed by simulation method. The results of this study showed that the energy saving effect of night-purge control with ERV is most effective in the case of 2 hours operation prior to the commencement of the first lass and when enthalpy based outdoor air cooling is used.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.756-761
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• 2012

Natural gas is converted in to LNG by chilling and liquefying the gas to the temperature of $-162^{\circ}C$, when liquefied, the volume of natural gas is reduced to 1/600 of its standard volume. This gives LNG the advantage in transportation. In this study, the effects of the pressure drop of refrigerant and natural gas in the LNG heat exchanger of cryogenic cascade refrigeration cycle were investigated and then the design criteria for the pressure drop of refrigerant and natural gas of the LNG heat exchanger were proposed. The pressure drop of the cascade liquefaction cycle was investigated and simulated using HYSYS software. The simulation results showed that the pressure drop in the LNG heat exchanger is set to 50 kPa considering the increase in the compressor work and COP of cryogenic cascade liquefaction cycle.

• Journal of Animal Environmental Science
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• v.14 no.1
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• pp.39-46
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• 2008

Experiments were carried out to evaluate the air speed distribution of an enclosed growing-finishing pig house in summer and winter. The data taken by experiments were compared to validate with the calculated air speeds by a commercial CFD code, FLUENT. Air basically enters into the house through Baffled slot Inlet and leaves through a exhaust fan attached on the Exhaust fan in exiting wall of the house. Air speeds were measured as $2{\sim}2.5m/s$ at the two side slot in winter and 0.8 m/s in summer. The validation showed that a CFD simulation is one of feasible methods to predict airspeed distribution in the growing-finishing pig house.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.905-910
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• 2013

The flow analysis has been made by applying the turbulent models in the helically coiled tubes of heat transfer. The k-${\varepsilon}$ and Spalart-Allmaras turbulent models are used in which the structured grid is applied for the simulation. The velocity vector, the pressure contour, the change of residuals along the iteration number and the friction factors are simulated by solving the Navier-Stokes equations to make clear the Reynolds number effect. The helical tube increases the centrifugal forces by which the wall shear stress become larger on the outer side of the tube. The centrifugal force makes the heat transfer rate locally larger due to the increase of the flow energy, which finds out the close relationship between the pressure drop and friction factor in the internal flow. The present numerical results are compared with others, for example, in the value of friction factor for validation.