• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.112-121
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• 1997

This study is focused on the development and selection of optimal cool tube system to maximize its thermal performance. Cool tube is devised to reduce the heating and cooling load of building by preheating or refreshing of intake air. Finite volume method was adopted to solve the conduction problem between the cool tube and earth. We examine the cool tube system for two operating periods, a short term(12 hours) and a long term(3 months). The results of short term operations reveal that condensation significantly influences and raises the exit air temperature. For long term operations, optimum conditions of cool tube system are obtained with variations of flow-rate, depth, length and diameter of cool tube.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.517-526
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• 1997

This study is focused on the development and selection of the optimal cool tube system to maximize its thermal performance. Cool tube is devised to reduce the heating and cooling load of building by preheating or refreshing of intake air with buried pipes. Finite volume method is adopted to solve the conduction problem between the cool tube and earth. We examine the cool tube system for two operating periods, a short term(12 hours) and a long term(3 months). The results of short term operations reveal that condensation significantly influences and raises the exit air temperature. For long term operations, optimum conditions of cool tube system are obtained with variations of flow-rate, depth, length and diameter of cool tube.

• Land and Housing Review
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• v.10 no.1
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• pp.25-32
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• 2019

In this study, the case analysis data on underground temperature are presented. In addition, numerical analysis of the ventilation load reduction plan was derived according to the residence schedule change for the building with cool tube. The research scope and method are as follows. The overall system principle was examined through reviewing the theory of the Cool tube system. Case study and analysis were conducted. Numerical simulation was used to examine the change in energy usage. Also, the change of load energy in case of varying amount of ventilation was derived based on actual building room schedule. When the Cool tube system was applied to the residential buildings, the cooling load was reduced from 3,331 kW to 193 kW, which showed a reduction effect of about 90%.The heating load was reduced from 42,276kW to 32,575kW by 23%.Also, result shows that the cooling load decreased by 24% and the heating load decreased by 66% when the number of ventilation according to the occupancy schedule was applied.

• KIEAE Journal
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• v.8 no.5
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• pp.11-16
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• 2008

This research has established CFD model on pit's cool-tube system through heat and air movement simulations, of which data was based on experimental and verification. This research work verified the effectiveness of the cool-tube system by analysing temperature, humidity and air current of the actually installed case. Also, we analysed heat transfer through air current simulation and the results are as followings. Firstly, we experiment on temperature, humidity and speed of air currents of the cool tube system with pit space during the month of May (spring). The average exterior temperature was $16.1^{\circ}C$, and $18.2^{\circ}C$ for the pit, $24.7^{\circ}C$ for the compressor room. Secondly, based on measured data of real case, we have analysed heat transfer through air current simulation and verified our proposed model. The actual measurement of average temperature of exhaust air of the pit's area is $19.7^{\circ}C$ with tolerance of $-0.33^{\circ}C{\sim}-0.6^{\circ}C$ compared to above simulations. Thirdly, having verified air current simulation model with formation of 260,000 and 1,000,000 cells, we could get reasonable near values with 260,000 cells. Lastly, the next step of research would be focused on proposing the best possible pit's cool-tube system after analysis of heat transfer of the air current simulation based on verified CFD model.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.296-301
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• 2003

A study on the engineering design and numerical thermo-hydraulic analysis for KSTAR TF coil structure cooling system has been conducted. The numerical analyses have been done to verify the engineering design of cooling using the commercial code, FLUENT and in-house code for calculating helium properties which varies with cooling tube's heat transfer. Through the engineering design process based on the steady heat balance concepts, the circular stainless steel tube with inner diameter of 4 mm for TF coil has been selected as cooling tube. From normal operation mode analysis results, total 28 cooling tubes were finally chosen. Also, three dimensional cool down analysis for TF coil with designed cooling tube was satisfied with next three design criteria. First is cooling work termination within a month, second is maximum temperature difference within 50 K in TF coil structure and third is exit helium pressure above 2 bar. Consequently, these cool down scenario results can afford to adopt as operating scenario data when KSTAR facilities operate.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.12
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• pp.1184-1190
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• 2012

This study is focused on the experimental analysis of the noise induced by phase change of refrigerant at the entrance of capillary tube. The refrigerant is usually two-phase condition when it flowed into the capillary tube. At the entrance of capillary tube, the phase condition of refrigerant is formed by sub-cool control. If it has sufficient sub-cool temperature, all of the vapor refrigerants turned to liquid, which means there is only liquid. Otherwise, the gas is coexisted. Based on this theory, we experiment on each case by changing sub-cool temperature using refrigerant-supplying equipment. The noise level is measured for each case and compared.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.681-688
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• 2014

Hydride reorientation behaviors of PWR cladding tubes under typical interim dry storage conditions were investigated with the use of as-received 250 and 485ppm hydrogen-charged Zr-Nb alloy cladding tubes. In order to evaluate the effect of typical cool-down processes on the radial hydride precipitation, two terminal heat-up temperatures of 300 and $400^{\circ}C$, as well as two terminal cool-down temperatures of 200 and $300^{\circ}C$, were considered. In addition, two cooling rates of 2.5 and $8.0^{\circ}C/min$ during the cool-down processes were taken into account along with zero stress or a tensile hoop stress of 150MPa. It was found that the 250ppm hydrogen-charged specimen experiencing the higher terminal heat-up temperature and the lower terminal cool-down temperature generated the highest number of radial hydrides during the cool-down process under 150MPa hoop tensile stress, which may be explained by terminal solid hydrogen solubilities for precipitation, and dissolution and remaining circumferential hydrides at the terminal heat-up temperatures. In addition, the slower cool-down rate generates the larger number of radial hydrides due to a cooling rate-dependent, longer residence time at a relatively high temperature that can accelerate the radial hydride nucleation and growth.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.18-20
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• 2003

Optimal processing and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from cool rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$ laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.

• The Journal of Korean Medicine
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• v.18 no.2
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• pp.148-154
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• 1997

In the pharmacology of traditional Korean medicine, each drug has its own specific characters. The different characters of drugs are employed to treat diseases, rectify the hyperactivity or hypoactivity of yin or yang, and help the body restore its normal physiological functions, consequently curing the diseases and restoring health. The various characters and functions of these drugs concerning medical treatment include drugs' properties, flavours, actions of lifting, lowering, floating and sinking, channel tropism, toxicity, etc. Among these theories, theory of properties and flavours of drugs provides the basis for drug analysis and application. 'Property' refers to the cold, hot, warm or cool nature of a drug. These properties of drugs are so sorted out according to the different actions of the drugs on the human body and thier therapeutic effects. Drugs which cure heat syndrome(yang syndrome) have a cold or cool property, whereas drugs which cure cold syndrome (yin syndrome) have hot or warm property Drugs of cold and cool-natured and drugs of warm and hot natures are of opposite properties. A cold-natured drug is different from a cool-natured on only in degree, and so is a warm-natured drug from a hot-natured drug. Most of the cool- or cold- natured drugs have the effects of clearing heat, purging fire, removing toxic substances, and nourishing yin, and are uese to cure heat syndromes. On the contrary, drugs of warm or hot nature usually have the effects of dispersing cold, warming up the interior, supporting yang, and treating collapse, and are therefore used to treat cold syndromes. We thought that the property of drug may be related to the autonomic nervous system in western medicine. In other words, drugs of warm or hot nature increase heart rate or acts like sympathomimetics, and drugs of cool or cold nature decrease heart rate or acts like para sympathomimetics . According to this hypothesis, we administrated some drugs to isolated rat right atrium in magnus tube. But there is no correlation between 'property' in traditional Korean medicine and autonomic nervous system in western medicine.

• KIEAE Journal
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• v.12 no.4
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• pp.89-95
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• 2012

At present, many countries are trying to reduce green gas emissions to mitigate the effects of these gases on climate change. Year after year, there have been efforts to cut energy use for heating and cooling. Heating and cooling systems, common in all forms of housing, are increasing due to the constant supply of new housing resulting from improvements in economic growth and the quality of life. Thus, studies related to the design of cooling and heating systems to improve energy efficiency are expanding. Among the new designs, radiant floor cooling and heating systems which use capillary tubes are becoming viable means of reducing energy use. Radiant floor cooling and heating systems which use capillary tubes are creative and sustainable systems in which cool and hot water is circulated into capillary tube which has small diameter. In this study, the cooling and heating performance of this type of capillary tube system is investigated in an experimental study and a simulation using TRNSYS. The results of the experimental study show that under a peak load, a capillary tube radiant floor cooling system using geothermal energy can achieve desired indoor temperature without an additional heat source. The set room air temperature is maintained while the floor surface temperature, PMV and PPD remain within the comfort range. Also, this system is more economic than a packaged air conditioner system due to its higher COP. The results of the simulation show that the capillary tube radiant floor heating system maintains set temperature more stable than a PB pipe radiant floor heating system due to its lower supply temperature of hot water. In terms of energy consumption, the capillary tube radiant floor heating system is more efficient than the PB pipe radiant floor heating system.