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서창갑,이영찬,조기조 동명정보대학교 1999 東明情報大學校論文集 Vol.2 No.-
Although User Information Satisfaction(UIS) has been widely accepted as a surrogate measure to evaluate the information system success, it is affected by the level of user perceptions such as the level of user expertise, interest, and purpose of the evaluation, and others. The purpose of this study is to investigate effects of the hybrid approach that reflects weighted value for users' characteristics. We suggest analytical hierarchical process(AHP) to put the weighted values that consider individual differences of perceptions, and analyze its usefulness with 16 and users and 116 IS staffs of 12 small-medium sized companies. This article identified the hybrid approach using AHP is more useful and reasonable than traditional UIS measurement instruments.
Kim, Yongchan,Seo, Kook-Jeong,Lee, Kyu-Jung,Park, Youn cheol The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.8
Evaporation heat transfer coefficients and pressure drops were measured for smooth and micro-fin tubes with R-22 and R-410A. Heat transfer measurements were performed for 3.0m long horizontal tubes with nominal outside diameters of 9.52 and 7.0mm over an evaporating temperature range of -15 to 5$\^{C}$, a mass flux range of 68 to 211kg/㎡s, and a heat flux range of 5 to 15kW/㎡. It was observed that the heat transfer coefficient increased with mass flux. Evaporation heat transfer coefficients of R-22 and R-410A increased as the evaporating temperature dropped at a lower heat flux. Generally, R-420A showed the higher heat transfer coefficients than R-22 in the range of low mass flux, high heat flux and high evaporating temperature. Pressure drop increased with a decrease of evaporating temperature and a rise of mass flux. Pressure drop of R-22 was higher than that of R-410A at the same mass flux.
타워형 태양열 발전 흡수기의 열유속에 따른 수순환 특성 연구
서호영(Seo Ho-Young),김종규(Kim Jong-Kyu),강용혁(Kang Yong-Heack),김용찬(Yongchan Kim) 한국태양에너지학회 2008 한국태양에너지학회 논문집 Vol.28 No.2
This paper describes water circulation characteristics of a water/steam receiver at various heat fluxes. The water/steam receiver for a solar tower power system is a natural circulation type. Experimental conditions of water and steam were set at a pressure of 5 bar and temperature of 151.8℃. The experimental device for the water/steam receiver consisted of a steam drum, upper/lower header. riser tubes, and down comer tube. The experiments were conducted by varying heat fluxes in terms of mass flow rate in each riser tube. However, the total mass flow rate on the riser tubes was fixed at 217.4 g/s. For the uniform heat flux, while the water temperature of the steam drum and upper header were kept at steady state, the temperature of the lower header was fluctuated. For the non-uniform heat flux, while the temperature of the steam drum was kept a steady state, the temperature difference increased in the right and left side of the upper header, and the temperature of the lower header was fluctuated.
Cho, Il Yong,Seo, HyeongJoon,Kim, Dongwoo,Kim, Yongchan Elsevier 2016 ENERGY Vol.112 No.-
<P><B>Abstract</B></P> <P>The cooling and heating performances of R410A and R32 multi-heat pumps with a sub-cooler vapor injection (SCVI) were measured and compared with variations in the outdoor temperature, compressor speed, and injection ratio. Optimum injection ratios were determined to obtain maximum cooling and heating performances at a given operating condition. In the cooling mode with the optimum injection ratios, the R410A and R32 multi-heat pumps with vapor injection showed 2.1%–6.3% higher cooling capacity than those without vapor injection. In the heating mode, the R410A and R32 multi-heat pumps with vapor injection showed 7.5%–13.9% higher heating capacity than those without vapor injection, while showing 2.6%–7.0% and 1.1%–4.7% higher COPs, respectively. In addition, the SCVI cycle was more effective for improving the cooling and heating performances under extremely hot and cold weather conditions, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The performances of the R410A and R32 multi-heat pumps were measured. </LI> <LI> Vapor injection (SCVI) was adopted in the R410A and R32 multi-heat pumps. </LI> <LI> Optimum injection ratios were determined to obtain the maximum performance. </LI> <LI> Comparison was conducted according to outdoor temperature and injection ratio. </LI> <LI> Vapor injection was more effective under extremely hot and cold conditions. </LI> </UL> </P>
열전소자를 이용한 싱글 및 캐스케이드 냉동시스템의 냉각 성능에 관한 연구
임창학(Changhak Lim),김동우(Dongwoo Kim),김용찬(Yongchan Kim),서국정(Kookjeong Seo) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.12
The purpose of this study is to improve the cooling performance of single and cascade refrigeration systems using thermoelectric modules. The system consists of a heat sink, fan, and thermoelectric module. The operating parameters considered in this study include power distribution between the first- and second-stage thermoelectric modules, air flow, and variable condensing unit. The cooling capacity increased with decreases in the temperature difference between hot and cold surfaces, but decreased with increases in the condensing temperature. The COP decreased with increasing electric power of the thermoelectric module because of the increased Joule heat. The cooling performance improvement using the thermoelectric module is represented by the freezer temperature.
Hydrolysis of Waste Cooking Oil in Sub-critical Water Condition
( Sufi Ullah Siddik Bhuyan ),( Taeha Kim ),( Ruri Lee ),( Myoungchul Shin ),( Kwanghyeon Song ),( Yongchan Seo ),( Younghwan Chu ) 한국폐기물자원순환학회(구 한국폐기물학회) 2014 한국폐기물자원순환학회 심포지움 Vol.2014 No.1
Hydrolysis of triacylglycerol(TAG) from fats and oils to glycerol and free fatty acid (FFA), also referred to as fat splitting, is an important reaction for the olechemical industry. Typically, hydrolysis is carried out at 100-260℃ and 100-7000 kPa using 0.4-0.15(w/w) initial water to oil ratio with or without catalysts. It is an endothermic reaction occurs in a stepwise manner where TAG is initially hydrolyzed to diacyglycerol (DAG) then to monoacylglycerol (MAG) and finally to glycerol. Water, in its subcritical state, can be used as both a solvent and reactant for the hydrolysis of triglycerides. subcritical water (150℃<T<370℃, 0.4<p<22Mpa) can act as an acid or base catalyst. To investigate milder reaction conditions, in this study, waste cooking oil and fresh soybean oils will be hydrolyzed to free fatty acids with deionized water under SC CO<sub>2</sub> medium in a batch reactor. Effects of the reaction temperature, time and solvent to feed ratio on FFA in the hydroysis at equilibrium will also observed for optimum conversion of oil. The reaction products will be analyzed by acid-base titration, GC FID and HPLC.