• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1150-1155
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• 1992

The cooling characteristics of a hot steel plate by a laminar impinging water bar were investigated experimentally. The dynamic parameters investigated were nozzle height L between nozzle and the hot plate, flow rate Q, and initial cooling temperature. Because the boiling phenomena on a hot steel plate are unsteady and change discontinuously, it is difficult to analyze the cooling characteristics directly. In this study the cooling efficiency was estimated by using the temperature decay rates and expansion speed of the water cooling zone. Temperature in the water cooling zone decreased rapidly and the radius of the water cooling zone expanded nearly in proportion to square root of the cooling time. With increasing initial temperature of a hot steel plate, the cooling efficiency became descendent. The cooling curve in the case of L/D = 30 showed the largest temperature decay rate and excellent cooling performance.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.3
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• pp.87-93
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• 2011

CNC lathe machining has been widely used for parts machining of vehicles, aircraft, ships, electronics, etc. because cost savings for shortening processing time and increasing productivity are great. In this study, the purpose is to investigate the effect of cooling methods such as oil mist, water-soluble cutting oils on the workpiece surface roughness with the cutting speed, cutting depth, tool nose radius and feed rate of CNC lathe machine as a parameter in the cutting process of the aluminum alloy 2024 which is used a lot recently on aircraft parts. It is found that oil mist is coolant and water-soluble cooled by cutting the experimental conditions, cutting speed and cutting depth without effecting the surface roughness value was constant.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.308-323
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• 2021

In this study, we aimed to evaluate the environmental changes in Jinhae Bay caused by cooling water using numerical modeling. Cooling water discharge volume from the results of Case 1 (10 m³ sec^-1) showed that the environmental changes in Jinhae Bay were extremely insignificant throughout the study period. In the simulation conditions of Case 2 (100 m³ sec^-1), there was a decrease in water temperature of approximately 1 - 3℃ within a 5 km radius from the discharge outlet. In Case 3 (1000 m³ sec^-1), a decrease in water temperature of up to 4 - 5℃ was observed within a radius of 8 km from the discharge outlet and cooling water discharge spread throughout the Bay. Growth rate of microalgae decreased by up to 15 % in November, whereas it increased by up to 6 % near the Hangam Bay in Case 3. From the above results, we confirmed that the environmental changes in Jinhae Bay due to cooling water discharged from Tongyeong LNG station are extremely insignificant. Moreover, it is expected that cooling water discharge could be utilized as a counter measure for 'red tide bloom' or 'macroalgae growth'.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.370-373
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• 2008

It is known that the temperatures of die, punch, holder and punch pad need to be kept different to get better formability in Mg sheet forming processes. Heating and cooling channels are usually equipped in each tool to assign different temperature. This study focused on the optimal design of the heating and cooling channels for a cross-shaped deep drawing die set. While the die and blankholder were heated to and kept at $250^{\circ}C$ by using heat cartridges, the punch and punch pad were kept at much lower temperature than that of the die and blankholder by water circulating through cooling channels. All the approaches were done by numerical analyses, aiming to maximize the cup height and to minimize the punch corner radius without any failure.

• Journal of computational fluids engineering
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• v.20 no.1
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• pp.39-46
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• 2015

In this research, we studied the pressure drop affecting on the internal surface roughness and the curvature radius of a U-tube, which is used for the cooling system in PWR(Pressurized Water Reactor). Using ANSYS-FLUENT, a commercial code based on CFD(Computational Fluid Dynamics) technique, we compared a Moody chart with the Darcy friction factor changed by a range of various surface roughness and Reynolds numbers of a straight pipe model. We studied the effect giving variation about a range of various surface roughness and the curvature radius of the full scale U-tube model. The material of the heat transfer tube is Inconel 690 used in the steam generator. We compared the velocity distribution of selected 4 locations, and derived the correlation between the surface roughness and the pressure drop for the U-tube of each representative curvature radius using the linear regression method.

• Clean Technology
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• v.22 no.1
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• pp.45-52
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• 2016

This study reports on the modeling and simulation of heat transfer in packaging boxes used for vaccine shipping. Both water and n-tetradecane are used as primary insulation materials inside a multi-slab system. The one-dimensional model, which is a spherical model using a radius equivalent to the rectangular geometry of container, is applied in this study. N-tetradecane with low thermal diffusivity and proper phase transition temperature exhibits higher heat transfer resistance during both heating and cooling processes compared to water. Thus, n-tetradecane is a better candidate as an insulating material for packaging containers for vaccine shipping. Furthermore, the developed method can also become a rapid and economic tool for screening appropriate phase change materials used as insulation materials with suitable properties in logistics applications.

• Design & Manufacturing
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• v.17 no.3
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• pp.8-14
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• 2023

In this study, basic research was conducted on manufacturing technology of thick-walled light guide a component that controls the light source of automobile lamps. As a preliminary study for manufacturing the final injection molded parts, a model for analyzing the influence of micro patterns on light guides is presented. The optical characteristics of the light guide were analyzed according to the change of the curvature radius of the micro-optical pattern, and the injection molding characteristics of the light guide according to the change of injection molding conditions were analytically evaluated. It was confirmed that the luminance uniformity improves as the R value decreases for changes in the micro-pattern R value, but it was confirmed that there are technical limitations in actual injection mold core processing and high-replication injection molding. Injection molding analysis showed that cooling channel design is very important compared to general injection molding due to thick-wall characteristics and thickness variation. It was also confirmed that the cooling channel has a great influence on the cycle time and birefringence result due to residual stress. As a result of analyzing the influence of filling time, holding condition, and cooling on shrinkage, it was found that the cooling water temperature has a significant effect on the shrinkage of ultra-fine light guide parts, and the holding condition also has a significant effect.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.614-617
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• 2000

To get the maximum diffusion boundary of thermal effluent of Youngkwang Nuclear Power Plant, paths of TGPS Buoy and temperatures of surface water are obtained to 4 times at spring tide during 1 year. According to the paths of TGPS Buoy, the flumes of thermal effluent are moved about 12km from outlet to SW or WSW direction. After 3∼4 times of tidal period the waters are reached to Chilsan Island because the ebb flow is more predominant than the flood flow in this area. At the spring and fall season, a sudden drop of surface water temperature is detected around 5km radius from the outlet. At the summer season, it is measured about 10km. On the other hand the flumes are continuously cooled down by the atmosphere condition at winter season.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.177-185
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• 2018

There is a need to study dust separator screens with good drainage efficiency while effectively filtering suspended solids and other contaminants entering the intake pumping station, the drainage pumping station and the mediation pumping station, the cooling water inlet of the power plant, and the like. In this paper, Numerical studies were conducted for the optimal design of the dust separator screen using the Coanda effect. The shape of the dust separator screen is important, such as the right curvature radius $R_1$ at the top of the dust separator screen and the left curvature radius $R_2$ at the top, h is the height difference and shape between the screen and the accelerating plate, and ${\theta}$ is the inclination angle of the screen. A total of 4 shape factors were set and the effects of Coanda and drainage performance of each element were compared and analyzed, the optimum length and size of each shape element were derived by classifying the shape elements into direct and indirect influences. Finally, it was possible to effectively filter foreign matter by narrowing the screen spacing, and the drainage performance was analyzed and optimized through numerical studies of dust separator screen.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.187-195
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• 2006

In this work, we introduce a newly constructed arc-jet device of 150 kW input power. The design of this device is a Huels type with a narrow downstream electrode. General features of this device are first described. From the measured values of electrical power input, heat discharged into cooling water, gas flow rate, and settling chamber pressure, average enthalpy was determined using the heat balance and sonic throat methods. Using the settling chamber pressure and average enthalpy values, the flow properties in the nozzle and the heat transfer rate to the stagnation point of a blunt body are calculated accounting for thermochemical nonequilibrium. The envelope of enthalpy, pressure, degree of dissociation, and heat transfer rate are presented. Stagnation temperature is predicted to be between 4630 to 6050 $^{\circ}K$, and the stagnation point heat transfer rate is predicted to be between 175 and 318 W/$cm^{2}$ for a blunt body of 3 mm nose radius. Degree of dissociation in the stagnation region of the blunt body exceeds 30%.