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RISS 인기검색어
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- 저자 : 김창덕 (검색결과 804 건)
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老朽施設物 집단의 건설 및 유지 보수 최적화를 위한 새로운 접근 방법 : 집합화(Aggregation) 와 매트리스 (Matrix)활용 방안 연구를 중심으로
김창덕 光云大學校 1995 論文集 Vol.24 No.-
The selection of replacement and maintenance alternatives for deteriorating facilities is complicated, because decisions are dynamic. Decisions become vastly complex for large deteriorating systems of thousands of deteriorating units, termed multi-unit deterioration faclilties in this research, especially under limited budgets. OR(Operations Research) techniques together with the advent of computers provide us with the improved decision-marking ability. Especially for complex decisions such as the above, the utilization of OR techniques is essential. Only integer programming(IP) provides truly optimal solutions, but it is very expensive even for a small deteriorating system, and it is practically impossible for a real-world system. This research explores the use of aggregation to provide the conceptual foundation for using linear programming (LP) techniques that can handle large deteriorating systems. It describes the processes and structures of aggregation that can best fit deteriorating systems with the unlimited number of units. It also develops and investigates the use of matrices that can capture the dynamic nature of the decision.
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老朽施設物 建設 및 補修 最適化를 위한 기존 모델 연구(1부)
김창덕 光云大學校 1993 論文集 Vol.22 No.-
Some facilities deteriorate over time and use, and replacement or maintenance is necessary as they deteriorate. Selecting replacement and maintenance alternative for these deteriorating facilities is challenging, because decisions are dynamic. Decision become particularly complex for large deteriorating systems of thousands of deteriorating units, especially under limited budges. Only integer programming provides truly optimal solutions, but it is expensive for even small problems, and it is practically impossible for systems of realistic size. This research surveys the current optimization models for the selection of construction and maintenance for multi-unit deteriorating facilities, analyzes their uses and limitations, and finally presents the analysis. This research is the part 2 of the research titled "A new framework for the selection of construction and maintenance for multi-unit deteriorating facilities."
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동일한 유입온도조건에서 R410A와 R22 적용 응축기의 특성비교
김창덕,이진호 대한설비공학회 2003 설비공학 논문집 Vol.15 No.12
R410A is considered as an alternative refrigerant to R22 for air conditioners. An experimental investigation was made to study the characteristics of the heat transfer and pressure drop for R410A flowing in a fin-and-tube heat exchanger used for commercial air- conditioning units. Experiments were carried out under the conditions of inlet refrigerant temperature of 60℃ and refrigerant mass flux varying from 150 to 250 kg/m2s for refrigerant side. The inlet air has dry bulb temperature of 35℃, relative humidity of 40% and air velocity varying from 0.68 to 1.6 m/s. Experiments show that air velocity decreased by 16% is needed for R410A than that of R22 for subcooling temperature of 5℃, which resulted in air-side pressure drop decrease of 15% for R410A as compared to R22. As a consequence, in order to provide the same design condition of a condenser, the fan requires lower electric-power consumption with R410A than that with R22.
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김창덕,강신형,박일환,이진호 대한설비공학회 2004 설비공학 논문집 Vol.16 No.5
It is well known that some key parameters, such as evaporating temperature, refrigerant mass flow rate, face velocity and inlet air temperature, have significant influence on the evaporator performance. However performance studies related to a humid environment have been very scarce. It is demonstrated that the refrigerant mass flow rate, heat flux, water condensing rate and air outlet temperature of the evaporator significantly increase with air inlet relative humidity. As the air inlet relative humidity increases, the latent and total heat transfer rates increase, but the sensible heat transfer rate decreases. The purpose of this study is to provide experimental data on the effect of air inlet relative humidity on the air and refrigerant side pressure drop characteristics for a slit fin-tube heat exchanger. Experiments were carried out under the conditions of inlet refrigerant saturation temperature of 7℃ and mass flux varied from 150 to 250 kg/m2s. The condition of air was dry bulb temperature of 27℃, air velocity varied from 0.38 to 1.6 m/s. Experiments showed that air velocity decreased 8.7% on 50% of relative humidity 40% of that at degree of superheat of 5℃, which resulted that pressure drop of air and refrigerant was decreased 20.8 and 8.3% for 50% of relative humidity as compared to 40%, respectively.
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증발기의 설계조건에서 공기측 열전달계수 및 압력강하 산출
김창덕,이진호 대한설비공학회 2003 설비공학 논문집 Vol.15 No.12
An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry and wet surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of frictionf``
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