• Korean Journal of Optics and Photonics
• /
• v.30 no.1
• /
• pp.1-7
• /
• 2019

MANPADS (man-portable air defense system) is a counterweapon system against enemy aircraft, tracking the MWIR (mid-wavelength of infrared) signature of the plume. Under foggy conditions, however, multiple scattering phenomenon caused by the particles affects the MWIR transmittance, and the MANPADS detection performance. Therefore, in this study we analyzed the lock-on range of MANPADS with varying fog conditions and plume characteristics. To analyze the optical extinction properties and transmittance in fog, Mie scattering theory and analytic solution of the radiative-transfer equation are utilized. In addition, we used flare signature as an alternative MWIR light source. We confirmed that the lock-on range could be noticeably reduced under conditions of mist, and proportional to the flare temperature.

• Nuclear Engineering and Technology
• /
• v.51 no.6
• /
• pp.1514-1524
• /
• 2019

Hydrogen-steam gas mixture may be injected into containment with flow regime varying both spatially and transiently due to wall effect and pressure difference between primary loop and containment in severe accidents induced by loss of coolant accident. Preliminary CFD analysis is conducted to gain information about the helium flow regime transition process from jet to buoyancy plume for forthcoming experimental study. Physical models of impinging jet and wall condensation are validated using separated effect experimental data, firstly. Then helium transportation is analyzed with the effect of jet momentum, buoyancy and wall cooling discussed. Result shows that helium distribution is totally dominated by impinging jet in the beginning, high concentration appears near gas source and wall where jet momentum is strong. With the jet weakening, stable light gas layer without recirculating eddy is established by buoyancy. Transient reversed helium distribution appears due to natural convection resulted from wall cooling, which delays the stratification. It is necessary to concern about hydrogen accumulation in lower space under the containment external cooling strategy. From the perspective of experiment design, measurement point should be set at the height of connecting pipe and near the wall for stratification stability criterion and impinging jet modelling validation.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1334-1336
• /
• 2001

In this study, laser ablation atomic fluorescence (LAAF) spectroscopy has been applied for a nanometer-scale surface analysis of Na-doped polymethyl methacrylate (PMMA). LAAF spectroscopy is a new sensitive element detection technique which involves atomizing of a sample by the laser ablation and detection of ablated plume by laser-induced fluorescence (LIF) spectroscopy. Using this technique in the detection of Na atoms with Na-doped PMMA, a detection limit is obtained as 36 fg for single laser shot. Further, the depth distribution in the sample is measured with a very high spatial resolution using a two-layer PMMA sample by observing the shot-by-shot LIF intensity from the Na atoms.

• Journal of the Korean Society of Safety
• /
• v.39 no.1
• /
• pp.96-103
• /
• 2024

The demand for mass calculation of offsite consequence analysis to conduct exhaustive single-unit or multi-unit Level 3 PSA is increasing. In order to perform efficient offsite consequence analyses, the Korea Atomic Energy Research Institute is conducting model optimization studies to minimize the analysis time while maintaining the accuracy of the results. A previous study developed a model optimization method using efficient plume segmentation and verified its effectiveness. In this study, we investigated the possibility of optimizing the model through particle size distribution setting by checking the reduction in analysis time and deviation of the results. Our findings indicate that particle size distribution setting affects the results, but its effect on analysis time is insignificant. Therefore, it is advantageous to set the particle size distribution as fine as possible. Furthermore, we evaluated the effect of multithreading and confirmed its efficiency. Future optimization studies should be conducted on various input factors of offsite consequence analysis, such as spatial grid settings.

• Nuclear Engineering and Technology
• /
• v.41 no.7
• /
• pp.953-968
• /
• 2009

It is important to accurately predict the temperature and density distributions in large stratified enclosures both for design optimization and accident analysis. Current reactor system analysis codes only provide lumped-volume based models that can give very approximate results. Previous scaling analysis has shown that stratified mixing processes in large stably stratified enclosures can be described using one-dimensional differential equations, with the vertical transport by jets modeled using integral techniques. This allows very large reductions in computational effort compared to three-dimensional CFD simulation. The BMIX++ (Berkeley mechanistic MIXing code in C++) code was developed to implement such ideas. This paper summarizes major models for the BMIX++ code, presents the two-plume mixing experiment simulation as one validation example, and describes the codes' application to the liquid salt buffer pool system in the AHTR (Advanced High Temperature Reactor) design. Three design options have been simulated and they exhibit significantly different stratification patterns. One of design options shows the mildest thermal stratification and is identified as the best design option. This application shows that the BMIX++ code has capability to provide the reactor designers with insights to understand complex mixing behavior with mechanistic methods. Similar analysis is possible for liquid-metal cooled reactors.

• Journal of Mechanical Science and Technology
• /
• v.17 no.9
• /
• pp.1380-1387
• /
• 2003

When a cold HPSI (High pressure Safety Injection) fluid associated with an overcooling transient, such as SGTR (Steam Generator Tube Rupture), MSLB (Main Steam Line Break) etc., enters the cold legs of a stagnated primary coolant loop, thermal stratification phenomena will arise due to incomplete mixing. If the stratified flow enters the downcomer of the reactor pressure vessel, severe thermal stresses are created in a radiation embrittled vessel wall by local overcooling. As general thermal-hydraulic system analysis codes cannot properly predict the thermal stratification phenomena, RG 1.154 requires that a detailed thermal-mixing analysis of PTS (pressurized Thermal Shock) evaluation be performed. Also. previous PTS studies have assumed that the thermal stratification phenomena generated in the stagnated loop side of a partially stagnated primary coolant loop are neutralized in the vessel downcomer by the strong flow from the unstagnated loop. On the basis of these reasons, this paper focuses on the development of a 3-dimensional thermal-mixing analysis model using PHOENICS code which can be applied to both partial and total loop stagnated cases. In addition, this paper verifies the fact that, for partial loop stagnated cases, the cold plume generated in the vessel downcomer due to the thermal stratification phenomena of the stagnated loop is almost neutralized by the strong flow of the unstagnated loop but is not fully eliminated.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.2
• /
• pp.150-158
• /
• 2018

Numerical simulation and experimental study on the thermal flow field of the micro turbojet engine have been carried out for the purpose of developing infrared reduction technology for aircraft. A circular basic nozzle and five rectangular nozzles with different aspect ratio were considered. The conditions for CFD analysis were derived from the analysis of the engine performance. The temperature distribution of the nozzle plume was measured using a temperature sensing system. The thrust of the rectangular nozzle with the aspect ratio 5 was reduced about 1.8% compared to the circular nozzle, and the thrust decreased with increasing the aspect ratio of the nozzle. In the case of thermal flow field, it was observed that, as the aspect ratio increases, the exhaust plume in the experiment was formed wider than in the CFD analysis.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.4
• /
• pp.103-110
• /
• 2018

Infrared signatures emitted from naval ships are mainly classified into internal signatures generated by the internal combustion engine of the ship and external signatures generated from the surface of the ship heated by solar heat. The internal signatures are also affected by the chemical components ($CO_2$, $H_2O$, CO and soot) of the exhaust plumes generated by the gas turbine and diesel engine, which constitute the main propulsion system. Therefore, in this study, the chemical composition ratios of the exhaust plumes generated by the gas turbines and diesel engines installed in domestic naval ships were examined to identify the chemical components and their levels. The influence of the chemical components of the exhaust plumes and their ratios on the infrared signatures of a naval ship was investigated using orthogonal arrays. The infrared signature intensity of the exhaust plumes calculated using infrared signature analysis software was converted to the signal-to-noise ratio to facilitate the analysis. The signature analysis showed that $CO_2$, soot and $H_2O$ are the major components influencing the mid-wave infrared signatures of both the gas turbine and diesel engine. In addition, it was confirmed that $H_2O$ and $CO_2$ are the major components influencing the long-wave infrared signatures.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.5
• /
• pp.37-42
• /
• 2014

In Korea while the dam or reservoir is an important water resource, the value of this water resource is deteriorating by thermal-induced stratification. To ameliorate the water quality of reservoir by breaking stratification the use of air diffuser system is now widespread in Korea. According to the previous research, dynamics of bubble plume and destratification efficiency depended upon two dimensionless groupings; Mh and Pn suggested by Asaeda et al (1993). However, these two variables only include Q, N, H, g, u. and installed Boryeong reservior in appropriate width of water aeration, air dose and number of installations after calculating by applying these figures. This paper is performed to find out effect analysis about water aeration improvement to break thermal stratification.

• Journal of Environmental Science International
• /
• v.4 no.2
• /
• pp.169-180
• /
• 1995

This Daper presents effective simulation of the dispersion of thermal discharge which can be relesed at Boryong power plant. Applied numerical models are finite difference method for hydrodynamic analysis and Masch-model comprised of conditions for ambient current velocity. Application of these models is done in Cheonsu Bay Summing up the results of this study are as follows; 1. It is found that the result for measurements of temperature appears high at southwardly Songdo on flood. The reason is that tidal currents which flowed north direction were accompanied with southwardly dispersed thermal discharge. A minute Particle of thermal Plume has a tendency to dispels inward Deacheon Bay. 2. According to the results of numerical experiment, maximum distance for thermal discharge dispersion appeared 10.8 km at lower part and 8.6 km at upper part with power plant outlet as starting point. 3. Comparative the numerical simulation and Airbone Multispectral Scanner indicated that thermal discharge should be verified separative phenomena. The simulated results were compared with field data set showing good agreement. It is concluded that these model can be simulated well.