• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.351-358
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• 2000

In a small centrifugal compressor system, a high-speed motor needs to be developed to drive impellers directly. Heat is generated by both electrical heating due to copper coil resistance and aerodynamic heating in the gap between the rotor and stator in a high-speed motor. Removal of the heat is essential to the design of such motors since most magnetic materials are brittle and can be easily fractured by the heat. In the present study the cooling flow fields and temperature distributions were analyzed by using computational fluid dynamics simulation for a high-speed motor which has air cooling system as well as water cooling system. In the analysis a conjugate heat transfer problem is solved by considering both convective heat transfer in the cooling system and conduction heat transfer in solid parts. Based on design drawings of a motor, air cooling system and water cooling system were analyzed to obtain temperature field and thus to check the coiling system performance. Also the cooling performance are studied for various flow rates of cooling air and water at the inlets.

• 설비공학논문집
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• 제18권4호
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• pp.304-311
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• 2006

Experiments on evaporative spray cooling on the square plate heaters with plain or micro-porous coated surfaces were performed in this study. Micro-porous coated surfaces were made by using DOM [Diamond particle, Omegabond 101, Methyl-Ethyl-Keton] method. In case of purely air-jet cooling, the micro-porous coating doesn't affect the cooling capacity. In spray cooling three different flow patterns (complete wetting, evaporative wetting, dryout) are observed on both plain and micro-porous coated surfaces. The effects of various operating conditions, such as water flow rate, particle size, and coating thickness were investigated on the micro-porous coated surfaces. It is found that the level of surface wetting is an important factor to determine the performance of spray cooling. It depends on the balance between absorbed liquid amount by capillary force over porosity and the evaporative amount. The micro-porous coated surface has largest cooling capacity, especially in the evaporative wetting zone. It is found that the effects of liquid flow rate and coating thickness are significant in evaporative wetting zone, but are not in complete wetting and dryout zones.

• 대한건축학회논문집:구조계
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• 제35권10호
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• pp.235-243
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• 2019

In South Korea, millions of poultry have died due to repeated heat waves every year. The purpose of this study is to analyze the characteristics of heating and cooling loads of chicken houses in Korea and to present an effective insulation and ventilation measures to minimize the damage of poultry due to summer heat wave and to save energy in chicken houses in winter. The heating and cooling loads of standard chicken house were calculated. As a result of the calculation of maximum heating load based on the minimum ventilation rate in winter, the outdoor air temperature requiring heating was $6{\sim}7^{\circ}C$ to keep the indoor air temperature of chicken houses as $24^{\circ}C$. The peak cooling load of chicken houses was mostly taken by the heat generated by chickens and the heat gain due to ventilation. The heat gain through building envelopes was as small as neglectable. Most of chicken houses is usually cooled by gigantic forced ventilation in summer in Korea. When the chicken houses are cooled by electric cooling machine such as cooler or air conditioner, it is more effective to keep minimum ventilation rate to reduce the maximum cooling load. To lower the temperature of supplying water to cooling pad, it is recommended to use the underground water below 10 meters from the ground if there is abundant underground water.

• 한국환경과학회지
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• 제13권3호
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• pp.189-196
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• 2004

Characteristics of urban wanning phenomenon were studied using degree days for three big cities(Seoul, Busan, Daegu) adjacent to airport. Time variation of the cooling and heating degree days was analyzed using the daily mean air temperature data measured at the six meteorological observatory for long-term periods(25～43years). The results for the big cities are as followings: 1) It was found that the heating degree days trended to decrease from year to year. 2) The cooling degree days were nearly unchanged during the same analysis periods. 3) The number of days calling for air-heating also tended to decrease as time passes. 4) Those of air-cooling were nearly unchanged during the same time. It suggests that the change of air-heating condition owing to urbanization came in evidence in the winter season, but that of air-cooling condition was slight in the summer season. On the other hand, the long-term trends of degree days were very small in airport areas except for Kimhae airport. Hence, the gaps of degree days between big cities and rural airport areas are increasing.

• International Journal of Air-Conditioning and Refrigeration
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• 제9권1호
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• pp.50-57
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• 2001

The thermal performance of cooling towers is affected by the temperature of inlet water, wet bulb temperature of entering air and water-air flow rate. In this stud${\gamma}$, the effects of these variables are simulated using NTU-method and experimentally investigated for the counter-flow cooling towers. The simulation program to evaluate these variables which affect the performance of cooling tower was developed. The maximum errors between the results of simulations and experiments were 3.8% under the standard design conditions and 5.4% under the other conditions. The performance was increased up to 46~50% as the water loading was increased from 6.8$m^3/hr{\cdot}m^2$ to 159$m^3/hr{\cdot}m^2$. The range was reduced up to 56~42% when the wet bulb temperature of the entering air was increased from 22${\circ}C$ to 29${\circ}C$.

• 대한가정학회지
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• 제35권5호
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• pp.239-248
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• 1997

to design nature-affinitive, reasonable and effcient thermal environment plannings and facilities, the holding patterns of heating-cooling facilities·accessory devices and residents' evaluation in Cheju Province were surveyed as well as residents' understanding for them. Major findings of this study are summarized as follows: 1) In the cooling system, the percentage of air-conditioner possessor was 19.4%, which was lower possessive rate than mainland's. The location of air-conditioner was mainly public area. That is, 55.3% of the location is livingroom, and the rest was Anbang. the general cooling accessory device was a fan. It was frequently used at the children's room and the dining room. The possessive patterns of air-conditioner depend on the characteristics of residents, such as the academic carrier and the average monthly income. Characteristics of house for air-conditioner possess depend on the location, house type, the size of floor space. 2) In the heating system, individual heating system reached to 57.3%. Heating accessory devices were oil stove and electric heating blanket. Only 32.2% of survey population were holders. 3) Residents preferred better ventilated room arrangement, which was characteristic of subtropical areas. 4) The preferred condition for heating-cooling facilities and accessory devices were strong solidity, less air pollution, and less noise.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.323-328
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• 2005

The objective of this study is to analyze the cooling performance of an air- cooling system for telecommunication equipment. Temperature variation and capacity were measured in an actual unit for telecommunication equipment. In addition, the cooling performance was measured by installing a silicon rubber heater as a heat source in a cabinet. The standard thermal load for telecommunication equipment was approximately 293 W, and the maximum temperature of the heated surface was $64.5^{\circ}C$. The average and maximum temperatures of the heated surface were proportional to the inlet air temperature. When the heat load increased from 293 W to 400 W, the maximum temperature of the heated surface was higher than $64.5^{\circ}C$ even though the inlet air temperature decreased from 25 to $11^{\circ}C$.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.18-24
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• 2015

In this study, a $CO_2$ air-conditioning system was investigated with different types of electrically driven compressors, parallel flow type gas cooler, four-pass type evaporator, internal heat exchanger integrated with accumulator, and electric expansion valve. The experimental study was conducted under various operating conditions (ie., different rotational compressor speeds, air inlet temperatures and air velocity coming into heat exchangers). The experimental results showed the cooling capacity was 3.5kW at $35^{\circ}C$ ambient temperature when the vehicle was idle (ie., the worst condition for cooling off the gas cooler). In terms of performance effect of the compressor, the e-RP model had a slightly better cooling capacity and coefficient of performance than the e-GR model under the same test conditions. An experimental equation for optimum cooling-performance control was also suggested based on the results. A high-pressure control algorithm for the super critical cycle was determined to achieve both maximum cooling performance and efficient energy consumption. The results from the experimental equation coincided with those of previous experimental studies.

• 대한설비공학회지:설비저널
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• 제17권6호
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• pp.686-695
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• 1988

An algorithm and a computer program were developed for the operational simulation of office building cooling system. Using this computer program, the following results were obtained. ${\bullet}$ There is a critical number of coil rows in AHU with which the cooling system can be operated in maximum efficiency. ${\bullet}$ Energy conservation can be achieved in an office building through TAB(Testing Adjusting and Balancing) of zone air volumes.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.225-226
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• 2016

Bottom ash generated in thermoelectric power plants could be used as substitutional fine aggregate such as pearlite of fireproof mortar due to its lightweight and porosity. Development of substitutional materials is necessary because pearlite has several problems such as production of carbon dioxide during manufacturing process and high price. This study is to confirm the possibility of air cooling process bottom ash for fireproof mortar as substitutional material of pearlite through basic experiment.