• Wind and Structures
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• v.11 no.6
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• pp.479-496
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• 2008

In this paper, computer simulation of wind flow around a single cooling tower with louver support at the base in the KAZERUN power station in south part of IRAN is presented as a case study. ANSYS FLOTRAN, an unstructured finite element incompressible flow solver, is used for numerical investigation of wind induced pressure load on a single cooling tower. Since the effects of the wind ribs on external surface of the cooling tower shell which plays important role in formation of turbulent flow field, an innovative relation is introduced for modeling the effects of wind ribs on computation of wind pressure on cooling tower's shell. The introduced relation which follows the concept of equivalent sand roughness for the wall function is used in conjunction with two equations ${\kappa}-{\varepsilon}$ turbulent model. In this work, the effects of variation in the height/spacing ratio of external wind ribs are numerically investigated. Conclusions are made by comparison between computed pressure loads on external surface of cooling tower and the VGB (German guideline for cooling tower design) suggestions.

• Journal of Power System Engineering
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• v.10 no.4
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• pp.50-55
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• 2006

An efficient cooling system for a piston of an automotive engine is very important. Therefore a large capacity gasoline engine or diesel engine has adopted the direct injection cooling system to increase its cooling efficiency. In this direct cooling system, an cooling oil is injected to a piston directly using an oil jet and this cooling oil flows through an oil gallery inside the piston. Flow rate and injection accuracy of this cooling oil are very important because these are main factors that have influence on its efficiency. The purpose of this study is to understand the changes of flow characteristics with various curvatures and diameters of an outlet nozzle and to check whether engine oil enters into the oil gallery well or not. From this study, we found that secondary flow was formed in a curved part of jet due to centrifugal force and irregular flow pattern appeared at the jet outlet. This pattern has influence on flow characteristics of engine oil entering the gallery. These simulation results have a good agreement with experiments.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.67-72
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• 2012

Novel Front End Module(FEM) with improved pedestrian protection is very important to reduce the severity of pedestrian injury. The FEM needs to have enough space from hood to absorb the energy from any pedestrian collision. In this study, the cooling performance of the FEM to cool the engine was investigated under 25% height reduction. The results indicated that the cooling performance analysis was about 86% level compared to that of the conventional FEM. Also, good qualitative agreement between CFD predictions and experimental measurements was found. This FEM needs the cooling performance enhancement for changed air flow path at the frontal part of vehicle. Therefore, we showed an improved performance using air guide setup and shape modification under the high load condition.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.811-814
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• 2001

Warpage analysis of bobbin, molded by injection molding process was performed. Concerned with a mold design, cooling system was designed based on Taguchi method, the distance between cavity wall and cooling channel was most influent factor amongst four design variables like an inlet temperature of coolant, a coolant flow rate, a diameter of cooling channel, and the distance between cavity wall and cooling channel. Optimal packing processes to reduce the warpage of molded part was analyzed based on the response surface method by considering holding pressure. Their optimal processing conditions were 9.4 seconds, 5.3 seconds, 15.2 seconds, and 85MPa, respectively.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.1
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• pp.25-31
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• 2009

Supercooled type ice storage system with aqueous solution (or water) may have trouble with non-uniform release of supercooling even though it contributes to the simplicity of system and ecological improvement. The non-uniform release increases the instability of the system because it may cause an ice blockage in pipe or cooling part. In order to suppress the release of the supercooling, a cooling experiment was tried to an ethylene glycol(EG) 3 mass% solution corresponding with pressurization. Also, the frequency ratio of the release of the supercooling was measured to the pressurization from 101 to 505 kPa. At results, the frequency ratio of supercooling release tends to decrease as the pressure of the aqueous solution increased in each cooling rate. Moreover, it tends to decrease as the cooling rate of the solution decreased in each pressure.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.923-924
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• 2007

due to the modification of ventilation system for variable speed high efficiency PMSM, the ventilation structure is analyzed in this part. First, a cooling structure was proposed for the variable speed PMSM. Through the contrast result of whole stress and speed distribution in the cooling channel by fluid field, the fans setting fashion is confirmed. By the studying of cooling structure for improved PMSM, the position of the cooling hole in the rotor is optimized by the finite element method. At last, the thermal field distribution of the motor is calculated by FEM. The calculated thermal rise is in accord with measured value, which provides effective basement for the design and safety operation of PMSM.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.81-85
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• 2011

Recently, the electronic parts are to be thinner plate, smaller size, light weight material and CPU, HDD and DRAM in all the parts have been produced on the basis of the high speed and greater capacity. Also, conventional goods have replaced a LED (Light-Emitting Diode) in lighting products so; such industry devices need to have cooling. To maximize all the performance on the heat-radiated products, the area of heat-radiated parts is required to be cooled for keeping the life time extension and performance of product up. Existing cooling systems are using radiant heat plate of aluminum, brass by extrusion molding, heat pipe or hydro-cooling system for cooling. There is a limitation for bringing the light weight of product, cost reduction, molding of the cooling system. So it is proposed that an alternative way was made for bringing to the cooling system. EP (Engineering Plastic) of low-cost ABS (Acrylonitrile butadiene styrene Resin) and PC (Polycarbonate) was coated with brass and the coating made the radiated heat go up. The performance of radiant heat plate is the similar to the existing part. We have studied experimentally on the radiated heat plate for the light-weight, molding improvement and low-cost. From now on, we are going to develop the way to replace the exiting plate with exterior surface of product as a cooling system.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.597-602
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• 2008

The experiment of performance about closed-wet cooling tower(CWCT) was conducted in this study. The test section has the cooling water that flows from top part of a heat exchanger that has an entrance of cooling water with one and multi path. The heat exchanger consists of 15.88mm tubes with ten rows and ten columns and staggered arrangement. In this experiment, heat and mass transfer coefficients and range are calculated with variations of cooling water and path. The results indicated that operating CWCT using two path have the high values of heat and mass transfer coefficients and range than one path.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.2
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• pp.59-65
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• 2013

The microstructures and hardness distributions of a large-sized high strength H-sectional steel with both V and Nb were systematically examined. The outer surface of the flange part was composed of martensite and bainite due to faster cooling, and had a high hardness value of approximately 310 Hv. However, the amounts of ferrite and pearlite increased and the hardness decreased with increasing the distance from the outer surface at the flange part, except the inner surface. High hardness value of about 290 Hv was measured at the upper surface of the web part having martensite and bainite. The hardness drastically decreased with increasing the web thickness, and then greatly rose again at the lower surface due to bainite formation caused by fast air cooling. The hardness of the flange part was higher than that of the web part due to the larger amount of low-temperature transformed phases, except for the lower surface of the web part. Nb-rich precipitates of 30 to 50 nm and V-rich precipitates less than 20 nm were observed at both flange and web parts. However, the particle size was smaller at the flange part than the web part, resulting in the higher strength of the flange part.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.8-14
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• 2022

A computer simulation was performed to investigate the heat source distribution and temperature distribution of a laser having multiple characteristics. To simulate the actual size of a welding specimen, the temperature distributions at 0 s, 1 s, and 2 s were analyzed by increasing the domain size to 50 mm in length and 25 mm in width in a material of the same thickness. As indicated by the results, because of the characteristics of metals with high thermal conductivity, the temperature at the welding center line and the temperature distribution at the offset position were not significant. When the core part was cooled by irradiating with a laser, it cooled at a rate of up to 500 ℃/s. In contrast, when the laser was irradiated to the ring part, the cooling proceeded at a rate of over 1800 ℃/s. Comparing the relative numerical values rather than the absolute values, it was found that the cooling rate was approximately 3.6 times faster when the laser was irradiated through the ring than when the laser was irradiated through the core. As a result of irradiating with the same heat source (at 100 W) into the core, ring, and ring + core, it was confirmed that the highest temperature was irradiated to the ring part and the lowest temperature was irradiated to the core part.