• Progress in Superconductivity and Cryogenics
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• v.20 no.2
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• pp.34-39
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• 2018

A cryogenic cooling system is designed for a 154 kV/ 2 kA three-phase hybrid type superconducting fault current limiter (SFCL). The superconducting modules of the SFCL have the operating condition of 71 K at 500 kPa. The total heat load of the SFCL including the cooling system is estimated at 9.6 kW. The cooling system of the closed loop is configured to meet the operating condition, depending on cooling methods of forced flow cooling and re-liquefaction cooling. The cooling system is composed of three cryostats with superconducting modules, cryocoolers, liquid nitrogen circulation pumps, a subcooler and a pressure builder. The basic cooling concept is to circulate liquid nitrogen between three SFCL cryostats and the cryocooler, while maintaining the operating pressure. The design criterion for the cooling system is based on the operation results of the cooling system for a 154 kV/2 kA single-phase hybrid SFCL. The specifications of system components including the piping system are determined according to the design criterion.

• Journal of the Korean Institute of Landscape Architecture International Edition
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• no.2
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• pp.120-129
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• 2004

Urban stream restoration projects can improve water quality, wildlife habitats, urban landscape, outdoor recreation spaces, and urban microclimate. The objectives of this research were to investigate temperature cooling effect of urban streams by using satellite imagery, to evaluate environmental variables related to stream cooling effect, and to estimate the cooling effect of the Cheonggye stream restoration project of Seoul, Korea. Findings of this research can be summarized as follows. First, a method of estimating temperature distribution around urban streams by using satellite imagery was developed. Scatter plots of distance from stream edges and average temperature obtained through multiple buffering were used for the estimation. Second, urban temperature cooling effect of streams was estimated by comparing background temperature and temperature of each buffer zone. Third, environmental factors affecting stream cooling effect were also identified. Fourth, the temperature cooling effect of the restoration project was estimated based on three scenarios. An estimated cooling effect based on the average cooling effect of existing tributaries showed the most significant effect; $2.0^{\circ}C$ lower than the present level at the edge of the renovated stream. It was estimated that the temperature of the same area would be $1.4^{\circ}C$ cooler than the present level if the cooling effect of the Yangjaechun was used as the bench mark But the effect would be $1.2^{\circ}C$ lower than the present level if environmental variables related to the temperature cooling effect of urban streams were used as the bench mark.

• Elastomers and Composites
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• v.57 no.2
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• pp.62-72
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• 2022

Passive daytime radiative cooling (PDRC) is attracting increasing attention as an eco-friendly technology that can save cooling energy by not requiring an external power supply. An ideal PDRC structure should improve solar reflectance and emissivity within the atmospheric spectral window. Early designs of photonic crystal materials demonstrated the benefits of PDRC. Since then, functional arrangements of polymer-based radiative cooling materials have played an important role and are rapidly expanding. This review summarizes the known inorganic, organic, and hybrid materials for PDRC. The review also provides a complete understanding of PDRC and highlights its practical applications.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.950-954
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• 2001

Gasoline engine manufacturers are currently considering designs that will result in low combustion air temperature for improvement of fuel consumption and emission levels. There are a variety of cooling systems that can be used to accomplish this goal. Coolong is therefore normally achieved through a balance of ram and fan action. This paper studies the various systems and compare the cooling performance for several conditions, based on a automotive engine. An experimental analysis was developed to predict the interaction of the fan system and the heat exchangers of the engine cooling system. The local temperature induced by the fan on the cooling system is measured. These experimental result were accomplished using air flow management techniques.

• 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 KSME Conference
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• 2000.11b
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• pp.341-346
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• 2000

A numerical simulation has been carried out for the engine cooling system. It is the important element to analysis of heat transfer process in cooling system for an automotive engine. Thus, the purpose of this simulator is to present useful information at the early stages of the design of the cooling system by enabling the development engineer to predict performance trends. This program has useful window interface for analysis of the cooling system and it is convenient for user to control data with relational database. The system was simulated and compared with experimental data. As a result, the inlet, outlet temperature of the radiator by the simulator agrees well with it. It is concluded that this simulation program is available in developing the cooling system for a new car.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.940-945
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• 2001

Gasoline engine manufacturers are currently considering designs that will result in low combustion air temperature for improvement of fuel consumption and emission levels. There are a variety of cooling systems that can be used to accomplish this goal. Cooling is therefore normally achieved through a balance of ram and fan action. This paper studies the various systems and compare the cooling performance for several conditions, based on a automotive engine. An experimental analysis was developed to predict the interaction of the fan system and the heat exchangers of the engine cooling system. The local temperature induced by the fan on the cooling system is measured. These experimental result were accomplished using airflow management techniques.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.456-459
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• 2005

Continuous cooling transformation behaviors were studied fur low carbon HSLA steels containing three different level $(1\~3\;wt\%)$ of Ni addition. Thermo-mechanical processing (TMP) simulations to construct continuous cooling (CCT) diagram were conducted by using Gleeble system. As cooling rate increased, pearlite, granular bainite, acicular ferrite, bainitic ferrite and lath martensite were transformed from deformed austenite. Fully bainitic microstructure were developed at all cooling rate condition in high Ni containing steel due to hardenability increasing effects of Ni. Ni also influenced the transformation kinetics. At the slowest cooling rate of $0.3^{\circ}C/s$, transformation delayed with decreasing Ni contents because of the diffusion of substitutional alloy elements. However, cooling rate slightly increased to $1^{\circ}C/s$, transformation kinetics accelerated with decreasing Ni contents because nucleation of bainite was sluggish due to hardening of residual austenite.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.908-912
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• 2013

Because of their longer operating times and larger size relative to conventional fans, the cooling fans mounted in buses consume larger amounts of energy. Most of the cooling fans mounted in a bus are connected to the engine by a viscous clutch. A viscous cooling fan's speed is determined by its fluid temperature, which is affected by the air flow through the radiator. The fan does not react immediately to the coolant temperature and in doing so causes unnecessary energy consumption. Therefore, the fuel economy of buses using viscous fans can be improved by changing to an electric cooling fan design, which can be actively controlled. In addition, electric power consumption is increased by using electric cooling fans. Thus, when electric fans are applied in conjunction with the alternator management system (AMS), the fuel economy is further enhanced. In this study, simulations were performed to predict coolant temperature and cooling fan speeds. Simulations were performed for both viscous and electric cooling fans, and power consumption was calculated. Additionally, fuel economy was calculated applying both the alternator management system and the electric cooling fan.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.4
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• pp.263-276
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• 1992

The transmission current in a power cable is determined under the condition of separate pipe cooling. To this end, the thermal analysis is conducted with the standard condition of separate pipe cooling system, which constitutes one of the underground power transmission system. The changes of transmission current in a power cable with respect to the variation of temperatures and flow rates of inlet cooling water as well as the cooling spans are also determined. As a consequnce, the corresponding transmission current is shown to vary within allowable limit, resulting in the linear variation of the current for most of the cable routes. The abrupt changes of current, however, for the given flow rate of inlet cooling water in some cooling span lead to the adverse effects on the smooth current transmission within the underground power transmission system. In practice, it is expected that the desinging of the separate pipe cooling system in conjunction with the evaluation of system capacity should take into account the effects of design condition on the inlet cooling flow rate.