• Solar Energy
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• v.16 no.2
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• pp.39-47
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• 1996

The horizontal thermal storage tank with heat pipe which is suitable for the sensible heat storage system is able to store a hot water from the heat source such as heating pad efficiently and to supply a hot water to load rapidly. And arrangement of heating pad play an important role in thermal flow and thermal storage efficiency. In this experiments, number of heating pad is ranged from three, five and nine, and when there is no change on number of heating pad, arrangements are two types of concentration-type and dispersion-type. Strong entrainment take place in the case of concentration-type of heating pad, and rapid temperature rise(${\Delta}{\doteqdot}1.6{\sim}3.2^{\circ}C$) in the tank is obtainable on the concentration-type than dispersion-type. In the constant number of heating pad, the concentration-type has the higher efficiency with about $5{\sim}6%$ than the dispersion-type Therefore, concentration-type of heating pad is an efficient design in constant number of heating pad.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.779-787
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• 2013

The effects of various nozzle configurations on infrared signature are investigated for the purpose of analysing the infrared signature level of aircraft propulsion system. A virtual subsonic aircraft is selected and then a circular convergent nozzle, which meets the mission requirements, is designed. Convergent nozzles of different configurations are designed with different geometric profiles. Using a compressible Navier-Stokes-Fourier CFD code, an analysis of thermal flow field and nozzle surface temperature distribution is conducted. From the information of plume flow field and nozzle surface temperature distribution, IR signature of plume and nozzle surface is calculated through the narrow-band model and the RadThermIR code. Finally, qualitative information for IR signature reduction is obtained through the analysis of the effects of various nozzle configurations on IR signature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1135-1139
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• 2017

Spatial distribution of chemical species in flame is a important indicator understanding the flame structure and combustion characteristics, and optical emission spectroscopy has been widely used for the measurement because of its simple and non-intrusive methodology. In this study, we suggest the feasibility of the measurement of chemical species (OH radical) distribution in rocket plume using optical emission spectrometer which was developed for the spatially resolved measurement along the line-of-sight. In order to predict the ground state concentration of species from the measured emission intensity by optical emission spectrometer, we consider thermal and chemical excitation mechanisms in flame, and assume thermodynamic equilibrium for the thermally excited species. We also present the spatial resolution and the correction of collection characteristics of the optical emission spectrometer depending on object distance.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.987-995
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• 2019

Steam jet condensation is of great importance to pressure suppression containment and automatic depressurization system in nuclear power plant. In this paper, the condensation processes of sonic steam jet in a quiescent subcooled pool are recorded and analyzed, more precise understanding are got in direct contact condensation. Experiments are conducted at atmospheric pressure, and the steam is injected into the subcooled water pool through a vertical nozzle with the inner diameter of 10 mm, water temperature in the range of $25-60^{\circ}C$ and mass velocity in the range of $320-1080kg/m^2s$. Richardson number is calculated based on the conservation of momentum for single water jet and its values are in the range of 0.16-2.67. There is no thermal stratification observed in the water pool. Four condensation regimes are observed, including condensation oscillation, contraction, expansion-contraction and double expansion-contraction shapes. A condensation regime map is present based on steam mass velocity and water temperature. The dimensionless steam plume length increase with the increase of steam mass velocity and water temperature, and its values are in the range of 1.4-9.0. Condensation heat transfer coefficient decreases with the increase of steam mass velocity and water temperature, and its values are in the range of $1.44-3.65MW/m^2^{\circ}C$. New more accurate semi-empirical correlations for prediction of the dimensionless steam plume length and condensation heat transfer coefficient are proposed respectively. The discrepancy of predicted plume length is within ${\pm}10%$ for present experimental results and ${\pm}25%$ for previous researchers. The discrepancy of predicted condensation heat transfer coefficient is with ${\pm}12%$.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2997-3009
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• 2023

The Passive containment Air-cooling System (PAS) can effectively remove the decay heat of the modular small nuclear reactor after an accident. The details of natural convection around the dome, which is a key part of PAS, were investigated numerically in the present study. The thermal dynamics around the dome were studied through the temperature, pressure and velocity contours and the streamlines. Additionally, the formation of the buoyant plume at the top of the dome was investigated. The results show that with the increase of Ra, the lift-off point moves toward the bottom of the dome, and the eddy under the buoyant plume grows larger gradually, which enhances the heat transfer. And the heat transfer along the dome surface with different truncation angles was investigated. As the angle increases, the heat transfer coefficient becomes stronger as well. Consequently, a newly developed heat transfer correlation considering the influence of truncation angle for the dome is proposed based on the simulated results. This study could provide a better understanding of natural convection around the dome of PAS and the proposed correlation could also offer more predictive value in the improvement of nuclear safety.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.2
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• pp.73-82
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• 1998

In order to simulate surface discharged heat dispersion in costal area, a 2-dimensional Eulerian-Lagrangian model for far field and semi-active particle tracking random walk model in near field has been combined. The mass of discharged heat water in near field has treated as particles with buoyancy and this is eventually converted to horizontal additive dispersion in random walk equations. This model is applied to both a simplified coastal geometry and a real site. In simple application it can simulate plume-like characteristics around discharging point than a near field-model, CORMIX/3. Actual application in the Chonsu Bay shows farther spreading of heat water in near field comparing the observed data, and this shows that the developed model might be applied with satisfaction.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.334-343
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• 2019

The Al-Zour coastal area, located in southern Kuwait, is a region of concentrated industrial water use, seawater intake, and the outfall of existing power plants. The Al-Zour LNG import facility project is ongoing and there are two issues regarding the seawater temperature in this area that must be considered: variations in water temperature under local meteorology and an increase in water temperature due to the expansion of the thermal discharge of expanded power plant. MIKE 3 model was applied to simulate the water temperature from June to July, based on re-analysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the thermal discharge input from adjacent power plants. The annual water temperatures of two candidate locations of the seawater intake for the Al-Zour LNG re-gasification facility were measured in 2017 and compared to the numerical results. It was determined that the daily seawater temperature is mainly affected by thermal plume dispersion oscillating with the phase of the tidal currents. The regional meteorological conditions such as air temperature and tidal currents, also contributed a great deal to the prediction of seawater temperature.

• Korean Journal of Hydrosciences
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• v.6
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• pp.67-79
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• 1995

The reattachment of buoyant efflluent to a shore in a crossflow is investigated experimentally. The effluent is prodeced by discharging heated water through a projected side channel into a confined crossflow of the same depth. In the projecting effluent, the size of recirculating region, which is formed by deflected thermal plume on the lee of the effluent, tends to increase, but the maximum temperature decreases in the direction of the crossflow and it has more uniform transverse spreading compared to non-projected type. The heat flux across the crossflow is found to be independent of the projceted length of the side channel under relatively high buoyancy flux on the contrary to low buoyancy flux. The reattachment of th effluent can be specified by both velocity ratio and densimetric Froude number, whereas only the velocity ratio is governing factor to the reattachment of the effluent in the case of non-projecting type.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1736-1741
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• 2003

The characteristics plasma flow of an atmospheric plasma torch used for thermal plasma processing is studied. In general, it is produced by the arc-gas interactions between a cathode tip and an anode nozzle. The performance of non-transferred plasma torch is significantly dependent on jet flow characteristics out of the nozzle. In this work, the distribution of gas flow that goes out to the atmosphere through a plenum chamber and nozzle is analyzed to evaluate the performance of atmospheric plasma torch. Numerical analysis is carried out with various angles of an inlet flow which can create different swirl flow fields. Moreover, the size of plasma plume is experimentally depicted.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.183-189
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• 2005

A modeling of a hydraulic-gun-aerator is proposed to set up a design procedure for such devices. The aerators are used to destroy any thermal stratification that are responsible for the degradation of water qualify of lakes. The aerator produces ascending flow by using air bubbies released instantly near the bottom of the lake into a cylindrical pipe installed vertically. Differently form the diffuser-aerators, they can pull up the cold, oxygen depleted water directly to the region of the free surface, and they are believed to work effectively especially for relatively deeper lakes. Their design procedure has not been established yet though, and we propose a model focusing on the exit flow velocity at the top of the aerator through the examination of presently operating devices.