이 연구는 화재에 노출된 구조물의 역학적 거동을 평가하기 위한 기반연구로서 화재 유동해석과 열응력해석의 통합 프레임워크를 확립하고 이를 강재와 콘크리트로 이루어진 대표체적에 적용한 결과를 제시하였다. 먼저 Fire Dynamics Simulator(FDS)를 이용해 임의의 화재곡선으로 모델링되는 화원으로부터 구조물 표면까지 유동해석을 실시하였다. 이를 통해 구조물 표면에서 시간에 따른 온도 분포를 계산하였고, 이 결과를 비선형 열응력해석에 경계조건으로 적용하였다. 이후의 과정은 화재의 성장 또는 감소에 따라 구조물 표면온도의 변화를 반영하는 열전달해석과 구조해석으로 이루어진다. 제시한 통합 프레임워크에 의해 화재 구조해석을 수행한 결과, 강재와 콘크리트의 대표체적 모두 동일한 하중이 작용할 때 상온 조건에서는 탄성 거동을 보였지만 화재로 인한 온도 조건을 고려할 경우 소성 거동을 보였다. 이는 구조물이 화재에 노출되는 경우 설계하중보다 작은 하중에서도 한계상태에 이를 수 있다는 것을 의미하며, 따라서 원전구조물이나 교량과 같은 중요 사회기반구조물의 설계 시 구조물의 화재거동 평가가 고려되어야 한다고 할 수 있다.

이 연구는 화재에 노출된 구조물의 역학적 거동을 평가하기 위한 기반연구로서 화재 유동해석과 열응력해석의 통합 프레 임워크를 확립하고 이를 강재와 콘크리트로 이루어진 대표체적에 적용한 결과를 제시하였다. 먼저 Fire Dynamics Simulator(FDS)를 이용해 임의의 화재곡선으로 모델링되는 화원으로부터 구조물 표면까지 유동해석을 실시하였다. 이를 통 해 구조물 표면에서 시간에 따른 온도 분포를 계산하였고, 이 결과를 비선형 열응력해석에 경계조건으로 적용하였다. 이후의 과정은 화재의 성장 또는 감소에 따라 구조물 표면온도의 변화를 반영하는 열전달해석과 구조해석으로 이루어진다. 제시한 통합 프레임워크에 의해 화재 구조해석을 수행한 결과, 강재와 콘크리트의 대표체적 모두 동일한 하중이 작용할 때 상온 조 건에서는 탄성 거동을 보였지만 화재로 인한 온도 조건을 고려할 경우 소성 거동을 보였다. 이는 구조물이 화재에 노출되는 경우 설계하중보다 작은 하중에서도 한계상태에 이를 수 있다는 것을 의미하며, 따라서 원전구조물이나 교량과 같은 중요 사회기반구조물의 설계 시 구조물의 화재거동 평가가 고려되어야 한다고 할 수 있다.

The heat transfer characteristics of a louver fin for a radiator are numerically analyzed to investigate the performance of radiator for automotive. The commercial code FLUENT is utilized to simulate a louver fin to analyze both the flow fields of air and the solid region of lover fin. The numerical analysis is performed with the variation of air mass flow rate. The results show that as mass flow rate increases, louver fin efficiency is nearly constant. The correlation of the average Nu is derived. The results of numerical study is useful in louvered fin design.

This research is to investigate the performance analysis of methanol fuel cell for flow channel with four different types of the channel (Serpentine I, II, Inter-digitated, Parallel) in the fuel cell stack. Velocity, pressure, temperature and density distributions of fluid over the flow domain of the flow channel are numerically calculated for the optimum design of flow channel with uniform inlet velocity. According to better water discharge and mutual gas reaction with low pressure drop and high density difference between inlet and outlet in the flow channel, Serpentine I type is of highest performance of the flow channel shapes in the present methanol fuel cell models.

In this study, the heat flow characteristics of natural convection was theoretically analyzed with time by changing various locations of heat trace with tube surface about enclosed circular tube by applying nominal tube diameter 90 mm of KS D 3507. Before carrying out CFD (Computational Fluid Dynamics) analysis, it is presumed that the boundary condition is the tube’s inside and outside fluid temperature of 273 °K, the tube surface heat flux according to the heat trace location of 16 W/m. The result confirmed that water of inside tube is occurred natural convection caused by density difference depending on temperature profile. Additionally, in case of heat trace location, the heat transfer and flow characteristics showed clearly that two-heat trace location =135° and 180° was more favorable distribution than one-heat trace appropriate location =135°.

This research is to investigate the performance analysis of micro gas turbine for power generation with three different numbers of the nozzle vane in the micro gas turbine. Velocity, pressure. and temperature distributions of fluid over the flow domain of the turbine and turbulent kinetic energy of three different turbine blades are numerically calculated for the optimum design of turbine blade with two different rotational speeds of the turbine blade (10000 and 20000 RPM). Ultimately, the energy-efficient and maximum power-generated shape of the nozzle vane are determined through two different rotational speeds of the turbine with three shapes of the nozzle vane (6, 8, and 12 EA).

본 연구에서는 저장볼트(storage vault)의 실험을 위하여 1/4 축소모델 내 튜브의 적정 발열량을 선정하고자 상사해석을 수 행하였다. 저장볼트에 대한 열 및 유동 해석을 우선적으로 수행하였고, 크기를 1/4로 축소한 저장볼트에 대하여 동일한 전 산해석을 수행하였다. 전산해석 결과를 바탕으로, 제안된 무차원수를 비교하여 원형모델과 온도분포와 유동분포가 유사하 게 되는 발열량을 선정하였다. 1/4 축소 저장볼트 내 튜브의 열유속이 1.3배일 때, 원형 저장볼트와 1/4 축소 저장볼트의 온 도장 및 유동장이 상사되었다. 이 때, 1/4 축소 저장볼트 내 발열량은 약 190 W이다.

A three-dimensional computational fluid dynamics code is developed for predicting nonequilibrium flowfields over Mars entry probes. The numerical scheme is based on the cell-vertex finite volume method for a prismatic unstructured mesh system. Internal energy excitations and chemical reactions with finite rates are considered by introducing the two-temperature model of Park. Eight chemical species, C, N, O, CO, N2, NO, O2, and CO2, and nine chemical reactions are considered in the calculations. The developed code is verified in terms of prediction of heat flux to the body surface near the stagnation point of a Mars entry probe flying with the velocity of 6 km/s. The calculated heat flux reasonably agree with the calculated result in the past studies.

The study on ice thermal storage system is to improve total system performance in actual air-conditioning facilities. This paper deals with experimental research to observe the characteristics of heat flow and the effect of ice thermal storage in case of three sizes of ice ball, which are included identification of ice thermal extraction. Diameters of three ice ball was 103mm, 96mm, and 76mm is equivalent to 0.45, 0.50 and 0.55 in porosity respectively. Also inlet geometric parameters are the perforator and distributor. Flow rate of brine were 2LPM, 4LPM and 6LPM and the temperature difference in dynamic parameter are 8℃, 10℃ and 12℃. Flow rate of brine used the liter per minute(LPM) for liquid measurement applications. The effect of brine flow rate on efficiency increased as the temperature difference and porosity increased. An adaption of a long-term storage in case of smaller porosity(ɛ=0.45) was available through experiments of outlet temperature responses.

Silicon carbide(SiC) layer is particularly important tri-isotropic (TRISO) coating layers because it acts as a miniature pressure vessel and a diffusion barrier to gaseous and metallic fission products in the TRISO coated particle. The high temperature deposition of SiC layer normally performed at 1500-1650˚C has a negative effect on the property of IPyC layer by increasing its anisotropy. To investigate the feasibility of lower temperature SiC deposition, the influence of deposition temperature on the property of SiC layer are examined in this study. While the SiC layer coated at 1500˚C obtains nearly stoichiometric composition, the composition of the SiC layer coated at 1300-1400˚C shows discrepancy from stoichiometric ratio(1:1). 3-7μm grain size of SiC layer coated at 1500˚C is decreased to sub-micrometer (＜ 1μm) -2μm grain size when coated at 1400˚C, and further decreased to nano grain size when coated at 1300-1350˚C. Moreover, the high density of SiC layer (≥3.19g/cm3) which is easily obtained at 1500˚C coating is difficult to achieve at lower temperature owing to nano size pores. the density is remarkably decreased with decreasing SiC deposition temperature.

An algebraic model for turbulent heat fluxes which is originally suggested by Suga & Abe is modified on the basis of the elliptic blending equation. In order to satisfy the heat transfer characteristics of near-wall region and the flow center region far away from the wall, the model coefficients of the algebraic heat flux model are modified by using the solution of the elliptic blending equation. The predictions of turbulent heat transfer in a plane channel flow have been carried out with constant wall heat flux and constant wall temperature difference boundary conditions respectively. Also, the predictions are performed at various Prandtl numbers to test the applicability of the model. The prediction results show that the distributions of the turbulent heat fluxes and mean temperature are well captured by the modified algebraic heat flux model

There are vertical wall to prevent of circulation or pollution during building of ocean structures like a dam and bridge in the harbors area and the sea. Inflow fluid and base of structure are important thing as one of the structural design factors for this interception wall like a vertical wall and watertight wall. In this study, it is revealed that at least 2,000 instantaneous velocity field data are required for ensemble average to get reliable turbulence statistics. The flow behind of vertical wall was investigated using the PIV system from this study. From the results, the large vortex flow developed in recirculation zone for one row wall and two vortex flows developed over two rows. Scale of the vortices in recirculation zone was decreased to 45% over three rows.

A 2D axisymmetric numerical analysis was performed to study the characteristics of charge process inside solar thermal storage tank. The porosity and heat transfer coefficient of filler material as well as inlet velocity of heat transfer fluid are selected as simulation parameters. The porosity is varied as 0.2, 0.5, and 0.8 to account for the effect of filler granule geometry. Two levels of the heat transfer coefficient is adopted to assess the heat transfer between heat transfer fluid and filler material. The inlet velocity is varied as 0.00278, 0.0278, and 0.278m/s. As both of the porosity and the heat transfer coefficient increase, the discrepancy of the temperature distributions between the filler and heat transfer fluid decreases. As the inlet velocity increases, the penetration depth of the heat transfer fluid increases proportionally.

A 2D axisymmetric numerical analysis was performed to study the characteristics of charge process inside solar thermal storage tank. The interfacial area density and inertial resistance of filler material are selected as simulation parameters. The interfacial area density is varied as 800, 2000, and 4000 1/m. The inertial resistance is varied as 1, 3, and 5 1/m. When the interfacial area density increases from 800 to 4000 1/m, the discrepancy of the temperature distributions between the filler and heat transfer fluid decreases. As inertial resistance increases from 1 to 5, both of the temperature and fluid flow pattern changes considerably.