CFD was used to study the change in the operation of the governor to check the effect of response delay due to residual air in the governor cylinder, which adjusts the pump RPM of the Turbine Driven Aux. Feed Water Pump(TD AFWP) in the Nuclear power plant. As a result of analysis, as the amount of internal air increased, the time delay also increased proportionally, and a time delay of up to 0.2 sec. occurred. As in the theory, it was confirmed that the cylinder operation delay occurred depending on the presence or absence of a compressive fluid such as air, but the time delay wat not enough to significantly affect the pump operation.

In this paper, numerical simulations were conducted to secure both flow distribution and uniform flow discharge through a wall mount type air sterilizer. In order to increase the reliability of the simulation results where there is no well-known validation case for air sterilizer, mesh sensitivity study was performed under the constraint that y+ set to one for k-w SST turbulent modeling for both the air sterilizer and the fan. The installation of various guides and structures was reviewed in the point of flow distribution and pressure drop inside the sterilizer, and the exhaust pressure conditions were predicted to secure uniform flow discharge at outlets. This study has been done based on the computational analysis during the development stage of the air sterilizer, and the results will be verified through physical testing after production of prototype.

Among the various causes of the vibration problem of the radial sluice gate used in Saemangeum, the effect of flow-induced vibration was studied by the method of computational fluid analysis. In this study, the effect on the flow-induced vibration of the Saemangeum radial sluice gate was evaluated by 2D unsteady flow numerical analysis using ANSYS Fluent. Gate opening cases of 0.2m, 0.3m, 0.4m, 0.5m, and 1.0m were analyzed. As a result, the flow-induced vibration characteristics due to the instability of turbulent flow were observed through FFT analysis. As the gate opening increases, the frequency of the maximum amplitude moves gradually to a lower frequency region with the reduction of the magnitude. Therefore the flow-induced vibration effects can be considered as small with the gate opening increase.

국내 자연재난 피해의 50%는 태풍에 의해 발생하며, 최근 태풍에 동반된 강풍에 의한 인명 피해가 빈번하게 발생하고 있다. 재난 피해 저감을 위한 재난 안전 교육의 일환으로 국내의 강풍체험시설은 대부분 제한된 공간에 설치되어 체험을 위한 내부 유동장의 효과적 설계가 필요하다. 이를 위해 본 연구에서는 전산유체역학 기법을 이용하여 강풍 체험장의 내부 유동장을 해석하였으며, 내부 구조 형상으로 인해 발생하는 압력 저항을 공간 저항으로 정의하였다. 기존 강풍 체험장에 대한 분석 결과 기존의 수평 방향 풍로 구조로 인해 매우 불균질한 내부 유동장이 형성되고 큰 공간 저항이 발생함을 확인하였다. 이를 개선하기 위하여 풍로를 수직 방향으 로 변경함으로써 공간 저항을 80% 가까이 감소시킬 수 있음을 확인하였으며, 체험장 내부 유동장의 균질도도 크게 향상되어 실질적 강풍 체험장 구현이 가능함을 확인하였다.

The objectives of this study were to develop the optimal structures of recirculating aquaculture tank for improving the removal efficiency of solid materials and maintaining water quality conditions. Flow analysis was performed using the CFD (computational fluid dynamics) method to understand the hydrodynamic characteristics of the circular tank according to the angle of inclination in the tank bottom (0°, 1.5° and 3°), circulating water inflow method (underwater, horizontal nozzle, vertical nozzle and combination nozzle) and the number of inlets. As the angle in tank bottom increased, the vortex inside the tank decreased, resulting in a constant flow. In the case of the vertical nozzle type, the eddy flow in the tank was greatly improved. The vertical nozzle type showed excellent flow such as constant flow velocity distribution and uniform streamline. The combination nozzle type also showed an internal spiral flow, but the vortex reduction effect was less than the vertical nozzle type. As the number of inlets in the tank increased, problems such as speed reduction were compensated, resulting in uniform fluid flow.

본 연구에서는 대면적을 지니는 CDI 모듈의 흐름 향상을 위하여 유체가 들어가는 유입구로부터 면적이 증가하는 직사각형 형태의 유로를 설계하였다. 이를 바탕으로 설계된 모듈 형태에 대해 공급수의 흐름성과 사영역의 유무를 파악하였고 CFD 전산 유체 역학 프로그램을 통해 유로 내의 내부 압력, 유선 그리고 속도 벡터 분포를 분석하였으며 실제 흐름 관측과 CFD 프로그램을 비교 분석하였다. 실험 결과 모든 유속 10, 20, 30 mL/min에서 유로 내 사영역이 거의 발생하지 않았으며 공급수의 흐름성도 일정하게 유지되어 추후 대면적을 가지는 CDI 공정에 적용이 가능할 것이라 판단된다.

In this study, the heat flow characteristics of wave heat exchanger was investigated by being applied to the white smoke reduction system. Through numerical analysis, the heat transfer and flow characteristics of the wave heat exchanger with the change of inlet condition of air-side and water-side were analyzed. To investigate the temperature, the absolute humidity, heat transfer rate, pressure drop and turbulence characteristics of the wave heat exchanger, the simulation analysis was conducted by using the commercial computational fluid dynamics software (Solidworks Flow Simulation) under uniform flow conditions. As the inflow rate of air decreased and the inflow temperature of water increased, the heat transfer coefficient of the wave heat exchanger decreased. When the experimental conditions of water-side were the same, the air outlet temperature and absolute humidity of the wave heat exchanger increased with increasing inflow rate of air. To reduce the white smoke, the air outlet temperature and absolute humidity of the wave heat exchanger must be reduced. Therefore, the lower the air velocity and the water inflow temperature into the wave heat exchanger, the more effective it is.

원자력을 이용한 황-요오드 수소생산 공정 중 황산용액을 이송하는 기존의 시스템과 달리 새로운 황산 이송장치는 벨로우즈 박스 내에서 벨로우즈 외측으로 고온 부식성 액체인 황산이 흐르고, 벨로우즈 내측으로는 냉각수가 흐르는 상태에서 주기 운동을 통해 황산용액이 펌핑 되도록 구성된다. 200 ℃ 이상의 고온 부식성 액체인 황산용액을 정량으로 이송할 수 있도록 장치의 주요부품인 벨로우즈 주변의 열해석을 통해 온도분포를 확인하여, 테프론 재질의 벨로우즈의 내식성 및 내열성을 파악하고, 장치의 안전하고 효율적인 운용을 위한 기초자료를 취득하고자 하였으며, 냉각수 입구직경 3 ㎝, 질량유량이 3.9199 ㎏/s로 고정한 경우 벨로우즈의 길이에 관계없이 테프론 변형온도 이하임을 알 수 있었다.

전산유동 수치모형을 이용하여 다양한 대기안정도 상태하에서 부산광역시내 승학산과 구덕산의 초고해상도 풍력자원을 평가하였다. 연구에 사용된 수치모형은 중규모와 미규모 기상현상의 재현에 널리 사용되는 전산유동 수치모형인 A2C이다. 대기안정도가 강할 때, 위치에너지의 크기가 상대적으로 강해지기 때문에 산을 넘어가는 경향이 나타난다. 반면 대기안정도가 약해지면서 산악후면의 후류 발생이 증대되며, 난류에너지가 증가한다. 그리고 연평균 풍력밀도, 난류운동에너지, 연직 바람전단력 분석을 통하여 구덕산 정상의 남쪽 부근이 다른 구역보다 가용 풍력자원이 풍부함을 확인하였다.

Flow and heat transfer characteristics of gas, and trajectories and cooling characteristics of droplets/particles in a gas atomizer were investigated by a numerical simulation using FLUENT code. Among several kinds of solution method, the k- turbulent model, power-law scheme, SIMPLE algorithm is adopted in this study. Momentum and heat exchange between a continuous phase(gas) and a dispersed phase(particle) were taken into account. Particle trajectories are simulated using the Lagrangian method, and Rosin-Rammler formula is used for the particle size distribution. Streamlines, velocities and pressures of gas, and trajectories, velocities and cooling rates of particles have been investigated for the various gas inlet conditions. Small but very intensive recirculation is found just below the melt orifice, and this recirculation seems to cause the liquid metal to spread radially. Particle trajectory depends on the particle size, the location of particle formation and the turbulent motion of gas. Small particle cools down rapidly, while large diameter particles solidify slowly, and this is mainly due to the differences in thermal inertia.

For material recovery of black carbon and pyrolysis oil, pyrolysis is considered as an alternative to combustion-based technologies for treatment of waste tire. This study investigated the heat transfer optimization in a pyrolysis reactor for waste tire chips with a capacity of 24 t/d. The reactor was required to have a larger heat transfer rate from hot gas to tire chips in the early stage of pyrolysis, whereas the rate in the later stage should be lower. This was to prevent thermal cracking of heavy compounds in the pyrolysis vapor and to improve the quality of black carbon. CFD was applied to analyze the flow and heat transfer in the complex geometry of the reactor for a total of nine design cases. It was found that modifications to control the distribution of gas flow rate along the reactor are more effective for the present reactor than adjusting the measures for heat transfer enhancement (such as fins). The ideal design improvement was to divide the reactor into two gas sections for a separate control of the flow rate, and to remove the fins of which its alignment perpendicular to the flow inhibits the hot gas from approaching the tube of tire chips.

컨테이너 크레인은 강풍으로부터 보호를 받기 위한 차폐물이 없는 곳에 존재하기 때문에 이상 기후 조건에 취약성이 있는 구조물이다. 본 연구에서는 붐 각도의 변화에 따라 풍동실험과 전산유동 해석을 사용하여 컨테이너 크레인의 구조물에 대한 풍하중의 영향을 수행하였다. 그리고 75m/s의 풍속을 컨테이너 크레인에 적용하였다고 가정하였을 때 컨테이너 크레인의 풍력 내구성 설계에 사용되는 데이터를 컨테이너 크레인 설계자에게 제공하고자 한다. 본 연구에서는 건축물 하중기준의 풍하중 설계기준에 따라 풍하중을 적용하였으며 풍향에 따른 영향을 분석하기 위해서 유동장을 10˚ 간격으로 분할하였다. 이를 바탕으로 풍동실험과 전산 유동해석을 수행하였으며 얻어진 결과들을 비교 연구함으로써 컨테이너 크레인의 구조설계에 필요한 풍하중을 분석하였다.