• Transactions of Materials Processing
• /
• v.27 no.3
• /
• pp.171-176
• /
• 2018

In this study, the cooling characteristics of dies were investigated in the hot stamping process of front pillars for automobile. Two identical dies were manufactured out of tool steels with different thermal conductivities. The dies were designed with curved channels for uniform cooling of the blank. Computational fluid dynamics (CFD) simulations were also carried out, which can consider the heat transfer among the coolant, die, and blank. Measured and simulated thermal histories of dies were compared, and it was shown that high conductivity tool steel has an excellent cooling capacity compared to conventional tool steel.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.4
• /
• pp.528-533
• /
• 2008

A closed circuit cooling tower having high temperature of cooling water and small water flow rate is investigated. To study the characteristics of the heat transfer of heat exchanges in a cooling tower with multi paths a numerical method is used. The results show that the staggered tube arrangements in a bank show better performance than aligned ones for temperature variation with various outer diameters of tube bundles. In case of one pass, the 15.88 mm tube case shows about 9% better performance than the 25.4 mm tube case. In two paths, the tube outside diameter of 15.88 mm show about 14.4% better results than the 25.4 mm diameter case.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.5
• /
• pp.320-326
• /
• 2000

The canned motor of 3-phase induction is used for main coolant pump(MCP). The type of motor is canned-motor that stator and rotor are welded by sealed can. So, cooling water flows in the air gap of the canned motor as an independent cycling cooling system from the air gap to yoke of the motor to prevent high temperature of stator can and to lubricate bearing. Heat exchange is occurred between cooling water in the air gap and cooling water from the exterior pump to prevent rising of temperature in the motor. I has to analyze the characteristics of can exactly because the loss and the heat in the can are very important to design MCP. Therefore, thermal analysis is studied considering the effect of eddy-current los induced in the can.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.2
• /
• pp.33-40
• /
• 1997

Recently, there are an increasing needs for high speed rotating spindle which is an important mechanical ele- ment for a high efficiency machine tool in order to shorten machining time and cut production costs. The heat gen- eration is the most important problem in the motor integrated spindle. In this study, the effects of temperature distribution and thermal behavior according to the oil-air lubrication and cooling conditions are investigate theo- retically and experimentally on the motor-integrated spindle under unloading condition. The experimental spin- dle system is composed with the angular contact steel ball bearings, oil-air lubrication, air or oil jacket cooling system. To analyze the thermal behavior and cooling characteristics for the motor integrated spindle, the analysis using the finite element method is carried out. The analytical results are compared with the experimental results.

• Journal of the Korean Society of Industry Convergence
• /
• v.21 no.5
• /
• pp.241-246
• /
• 2018

The engine cooling system is a device that keeps the temperature of the engine room at a proper level by driving the cooling fan when the engine room temperature that occurs during driving is above a certain temperature. Recently, the vehicle cooling system has been changed to electronic system. Therefore, in this paper, we will analyze the clutch operation characteristics for designing a superior electronic fan clutch. For this purpose, an electronic fan clutch was designed and a test bed for performance evaluation was constructed and analyzed.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.77-82
• /
• 2000

Parametric study fur the cooling characteristic investigation of a notebook PC mounted with heat spreader has been numerically performed. Two oases of air-blowing and air-exhaust at inlet were tested. The cooling effect on Parameters such an, velocities of air-blowing and air-exhaust, materials of heat spreader, and CPU powers were simulated for two cases. Cooling performance in the case of air-blowing was better than the case of air-exhaust.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.1
• /
• pp.23-28
• /
• 2007

This study aims to find out cooling characteristics of TMA(Tri-Methyl-Amine, $(CH_3)_3N$) 25wt%-water clathrate compound with ethanol($CH_3CH_2OH$) such as supercooling, phase change temperature and specific heat. For this purpose, ethanol is added as per weight concentration and cooling experiment is performed at $-6{\sim}-8^{\circ}C$, cooling heat source temperature, and it leads the following result. (1) Phase change temperature is decreased due to freezing point depression phenomenon. Especially, it is minimized as $3.8^{\circ}C$ according to cooling source temperature in case that 0.5wt% of ethanol is added. (2) If 0.5wt% of ethanol is added, average supercooling degree is $0.9^{\circ}C$ and minimum supercooling is 0.8, $0.7^{\circ}C$ according to cooling heat source temperature. The restraint effect of supercooling is shown. (3) Specific heat shows tendency to decrease if ethanol is added. It is $3.013{\sim}3.048\;kcal/kg^{\circ}C$ according to cooling heat source temperature if 0.5wt% of ethanol is added. Phase change temperature higher than that of water and inhibitory effect against supercooling can be confirmed through experimental study on cooling characteristics of TMA 25wt%-water clathrate compound by adding additive, ethanol. This can lead to shorten refrigerator operation time of low temperature latent heat storage system and improve COP of refrigerator and efficiency of overall system. Therefore energy can be saved and efficiency can be improved much more.

• Wind and Structures
• /
• v.29 no.4
• /
• pp.235-246
• /
• 2019

Wind loading is one of important loadings that should be considered in the design of large hyperbolic natural-draught cooling towers. Both external and internal surfaces of cooling tower are under the action of wind loading for cooling circulating water. In the previous studies, the wind loads on the external surface attracted concernedly attention, while the study on the internal surface was relatively ware. In the present study, the wind pressure on the internal surface of a 220 m high cooling tower is measured through wind tunnel testing, and the effect of ventilation rate of the packing layer on internal pressure is a major concern. The characteristics of internal wind pressure distribution and its effect on wind-induced responses calculated by finite element method are investigated. The results indicate that the wind loading on internal surface of the cooling tower behaves remarkable three-dimensional effect, and the pressure coefficient varies along both of height and circumferential directions. The non-uniformity is particularly strong during the construction stage. Analysis results of the effect of internal pressure on wind-induced responses show that the size and distribution characteristics of internal pressure will have some influence on wind-induced response, however, the outer pressure plays a dominant role in the wind-induced response of cooling tower, and the contribution of internal pressure to the response is small.

• Wind and Structures
• /
• v.28 no.5
• /
• pp.299-313
• /
• 2019

In order to examine the effects of different wind deflectors on the wind load distribution characteristics of extra-large cooling towers, a comparative study of the distribution characteristics of wind pressures on the surface of three large cooling towers with typical wind deflectors and one tower without wind deflector was conducted using wind tunnel tests. These characteristics include aerodynamic parameters such as mean wind pressures, fluctuating wind pressures, peak factors, correlation coefficients, extreme wind pressures, drag coefficients and vorticity distribution. Then distribution regularities of different wind deflectors on global and local wind pressure of extra-large cooling towers was extracted, and finally the fitting formula of extreme wind pressure of the cooling towers with different wind deflectors was provided. The results showed that the large eddy simulation (LES) method used in this article could be used to accurately simulate wind loads of such extra-large cooling towers. The three typical wind deflectors could effectively reduce the average wind pressure of the negative pressure extreme regions in the central part of the tower, and were also effective in reducing the root of the variance of the fluctuating wind pressure in the upper-middle part of the windward side of the tower, with the curved air deflector showing particularly. All the different wind deflectors effectively reduced the wind pressure extremes of the middle and lower regions of the windward side of the tower and of the negative pressure extremes region, with the best effect occurring in the curved wind deflector. After the wind deflectors were installed the drag coefficient values of each layer of the middle and lower parts of the tower were significantly higher than that without wind deflector, but the effect on the drag coefficients of layers above the throat was weak. The peak factors for the windward side, the side and leeward side of the extra-large cooling towers with different wind deflectors were set as 3.29, 3.41 and 3.50, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.1
• /
• pp.82-87
• /
• 2005

The purpose of this study is to suggest the characteristics and actual state of energy consumption by the analysis of energy consumption data in an office building. This study examines and analyzes daily and monthly energy consumption of an office building located in Seoul, Korea regarding type of load and business classification within a building. The results are as follows. 1) Energy consumption of office building for each type of load show similar consumption patterns, regardless of seasons such as cooling period and heating period. 2) Out of all annual energy consumption, consumption for lighting took about $43\;\%,$ general electric Power about $23\;\%,$ emergency power $25\;\%,$ computer center $5\;\%$ and cooling power $4\;\%,$ showing that the consumption for lighting was highest, and the percentage of energy consumption for cooling power for operation of cooling facilities took the lowest percentage. 3) Annual gas consumption used for heating and hot water supply were $38,\;36\;\%$ for officetel and office respectively, and $26\;\%$ for arcade. 4) Electricity consumptions used for cooling power for each use of building, office and officetel recorded in July and August of cooling seasons. Even though it shows different patterns for each month, energy consumption showed unique pattern throughout the cooling seasons.