• Journal of the Korean Ceramic Society
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• v.34 no.7
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• pp.767-773
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• 1997

Thermal shock behavior of alumina ceramics were studied by quenching the heated alumina specimen into the water of various temperatures over 0~10$0^{\circ}C$. The critical thermal shock temperature difference ( Tc) of the specimen decreased almost linearly from 275$^{\circ}C$ to 20$0^{\circ}C$ with increase in the cooling water temperature over 0~6$0^{\circ}C$. It is probably due to the increase of the maximum cooling rate which is dependent of the convection heat transfer coefficient. The convection heat transfer coefficient is a function of the temperature of the cooling water. However, the critical thermal shock temperature difference( Tc) of the specimen increased at 25$0^{\circ}C$ over 80~10$0^{\circ}C$ due to the film boiling of the cooling water. The maximum cooling rate, which brings about the maximum thermal stress of the specimen in the cooling process, was observed to increase linearly with the increase in the quenching temperature difference of the specimen due to the linear relationship of the convection heat transfer coefficient with the water temperature over 0~6$0^{\circ}C$. The critical maximum cooling rate for thermal shock fracture was observed almost constant to be about 260$\pm$1$0^{\circ}C$/s for all water temperatures over 0~6$0^{\circ}C$. Therefore, thermal shock behavior of alumina ceramics is greatly influenced by the convection heat transfer coefficient of the cooling water.

• Journal of Environmental Health Sciences
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• v.35 no.5
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• pp.411-416
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• 2009

This study was initiated to improve the cooling water quality by chemical coagulation and sedimentation in steel mills. Due to the inefficient flocculation in the settling tanks of blast furnace cooling water systems, the solid particles in the cooling water overflow accumulate and clog the cooling system. To protect the cooling water system from such fouling, proper flocculants must be continuously used. Laboratory tests were performed for the indirect cooling water system of a plate mill. The batch test in the gas scrubbing cooling water system of a blast furnace showed that the proposed coagulant was more effective for the improvement of coagulation and sedimentation than the existing one. During the tests, cationic flocculants were more effective than use of only an anionic flocculant. The suggested combination of anionic and cationic flocculants can probably improve the turbidity removal efficiency of the cooling water. Proper control of the overflow rate by the designed residence time would help turbidity removal efficiency in the settling tank. In addition, the settling can be enhanced by adopting rapid and slow mixing alternatively. Scale problems in blast furnace cooling water system were reduced to some extent by efficient settling.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1475-1480
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• 2013

In this paper, the basic design study of a water-cooling jacket, which have reported no cases for applying to railway traction motors so far, were conducted for applying to Interior Permanent Magnet Synchronous Motor (IPMSM) for railway vehicles. The basic thermal characteristics analysis of the 110kW-class IPMSM was performed by using 3-dimentional thermal equivalent network method. The necessary design requirements of the water-cooling jacket were derived by analyzing the results of the basic thermal properties. Next, the thermal characteristics analysis technique was established by using the equivalent model of the solenoid-typed pipe to be installed on the inside of the water-cooling jacket for 110kW-class IPMSM. Finally, a design model of 6kW-class water-cooling jacket was derived through the analysis of various design parameters.

• The KSFM Journal of Fluid Machinery
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• v.14 no.3
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• pp.33-38
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• 2011

Medicated water electrolysis apparatus, which electrolyzes water into acidic water and alkaline water, was in the spotlight as becoming known the effect of alkaline water. It is known as good for health as removing active oxygen in the human's body and promoting digestion. But, the customers could not get that desired water temperature because these apparatuses are directly connected with a water pipe. So, the cooling system was developed for controlling the temperature of the alkaline water. One of the typical way is to store water in water tank and control the temperature. But, in this way, storing water can be polluted impurities coming from outside. For protecting this pollution, the cooling system based on indirect heat exchange method through phase change between water and ice was developed. In this study, we have calculated efficiency of the cooling system with phase change by experiment and commercial CFD(Computational Fluid Dynamics) code, ANSYS CFX. To consider the effect of latent heat that is generated by melting ice, we have simulated two phase numerical analyses used enthalpy method and found the temperature, velocity, and ice mass distribution for calculating the efficiency of cooling. From the results of numerical analysis, we have obtained the relationship between the cooling efficiency and each design factor.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.20-26
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• 2019

This study was conducted on cooling systems in which, for the first time at home and abroad, cold water panels are embedded in the walls of small buildings for radiant cooling by heat absorption with cold water. In summer, cold water is circulated through cold water (chiller) circulation tubes embedded in three walls (two side walls and one rear wall) of a building to implement radiant cooling by the coldness of the water. From the results of this study, the experimental and theoretical natural convection heat transfer coefficients were relatively well-matched over the entire experimental range, thereby verifying the reliability of the experimental results. The surface temperature reduction rate of the walls in which cold water panels are embedded was large whereas that of the walls where no cold water panels are embedded was very small.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.5
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• pp.249-256
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• 2010

Water jet impingement cooling has been widely used in a various engineering applications; especially in cooling of hot steel plate of steelmaking processes and heat treatment in hot metals as an effective method of removing high heat flux. The effects of cooling water temperature on water jet impingement cooling are primarily investigated for hot steel plate cooling applications in this study. The local heat flux measurements are introduced by a novel experimental technique that has a function of high-temperature heat flux gauge in which test block assemblies are used to measure the heat flux distribution during water jet impingement cooling. The experiments are performed at fixed flow rate and fixed nozzle-to-target spacing. The results show that effects of cooling water temperature on the characteristics of jet impingement heat transfer are presented for five different water temperatures ranged from 5 to $45^{\circ}C$. The local heat flux curves and heat transfer coefficients are also provided with respect to different boiling regimes.

• Restorative Dentistry and Endodontics
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• v.44 no.1
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• pp.3.1-3.10
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• 2019

Objectives: It was the aim of this study to evaluate the effect of cooling water temperature on the temperature changes in the pulp chamber and at the handpiece head during high-speed tooth preparation using an electric handpiece. Materials and Methods: Twenty-eight intact human molars received a standardized occlusal preparation for 60 seconds using a diamond bur in an electric handpiece, and one of four treatments were applied that varied in the temperature of cooling water applied (control, with no cooling water, $10^{\circ}C$, $23^{\circ}C$, and $35^{\circ}C$). The temperature changes in the pulp chamber and at the handpiece head were recorded using K-type thermocouples connected to a digital thermometer. Results: The average temperature changes within the pulp chamber and at the handpiece head during preparation increased substantially when no cooling water was applied ($6.8^{\circ}C$ and $11.0^{\circ}C$, respectively), but decreased significantly when cooling water was added. The most substantial drop in temperature occurred with $10^{\circ}C$ water ($-16.3^{\circ}C$ and $-10.2^{\circ}C$), but reductions were also seen at $23^{\circ}C$ ($-8.6^{\circ}C$ and $-4.9^{\circ}C$). With $35^{\circ}C$ cooling water, temperatures increased slightly, but still remained lower than the no cooling water group ($1.6^{\circ}C$ and $6.7^{\circ}C$). Conclusions: The temperature changes in the pulp chamber and at the handpiece head were above harmful thresholds when tooth preparation was performed without cooling water. However, cooling water of all temperatures prevented harmful critical temperature changes even though water at $35^{\circ}C$ raised temperatures slightly above baseline.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.1
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• pp.67-71
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• 2014

The well tightness of the coal mining water-cooling explosion-proof motor results in difficult heat dissipation, high hydraulic pressure is needed to increase the cooling effect. However, high hydraulic pressure may lead motor shell to deform, which makes it difficult to change the motor and maintain the motor unit. The method of adding keyhole caulk weld spots on the outer cooling water jacket was proposed to solve the problem. Based on the elasticity mechanics equations and the principle of finite element method the stresses and the deformations of the traditional and novel outer cooling water jacket were calculated separately. A hydraulic pressure experiment of the both cooling water jackets was constructed. Obviously, the stress and the deformation of the novel cooling water jacket are lower. The experimental result is consistent with the simulation results. It is effective to reduce the stress and the deformation of the cooling water jacket by adding the keyhole caulk weld spots.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.4
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• pp.39-45
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• 2019

The operational conditions such as cooling tower water pump flow rate, cooling tower fan flow rate, and chiller capacity in heat source equipment, and supply air temperature and chilled water temperature in air conditioner are considered to study the effects on energy consumption for central cooling system by using TRNSYS program. As a result, the optimal values of supply air temperature and chilled water temperature for minimal total energy consumption are 12℃ and 8℃. And if maximum values of cooling tower water pump and fan flow rate is decreased from 100% to 40%, energy consumptions are increased 170MJ/day and 63.2MJ/day, respectively.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.249-256
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• 2009

The cooling technology of power conversion semiconductors in the propulsion system for the HEMU(High Electrical Multi Unit) are applied in water cooling method and phase change method such as the immersed type and the heat pipe type. This research designs and manufactures the water cooling system that could cool about heat load Q=2kW and performance tests to apply it by an electric power conversion semiconductors(IGBT) cooling technology. Experimental condition made change of a flow rate, an air velocity and a heat load to confirm operation characteristics of water cooling device, and when is heat load 2kW, air velocity 20 m/s, and water flow rate 7kg/s, it is about $80^{\circ}C$ to temperature of cooling plate.