• Journal of Advanced Marine Engineering and Technology
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• 제27권1호
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• pp.108-116
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• 2003

In this paper, the experimental results of condensation heat transfer were reported for the plate and shell heat exchangers(P&SHE) using R-l34a. An experimental refrigerant loop has been established to measure the condensation heat transfer coefficient of R-l34a in a vertical P&SHE. Two vertical counter flow channels were formed in the P&SHE by three plates of geometry with a corrugated trapezoid shape of a chevron angle of 45$^{\circ}$. Downflow of the condensing R-l34a in one channel releases heat to the cold up flow of water in the other channel. The effect of the refrigerant mass flux, average heat flux, system pressure and vapor quality of R-l34a on the measured data were explored in detail. The results indicate that at a higher vapor quality the condensation heat transfer coefficients are significantly higher. Condensation heat transfer coefficients were increased when the refrigerant mass flux was increased. A rise in the average heat flux causes an slight increase in the hr. Finally, at a higher system pressure the hr is found to be lower. Correlation is also provided for the measured heat transfer coefficients in terms of the Nusselt number.

• Journal of Pharmaceutical Investigation
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• 제10권4호
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• pp.8-22
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• 1980

In order obtain some new antibacterial agents, seven new 2-ethoxymethyl-3-(5-nitro-2-furyl) acrylamide derivatives were synthesized by condensing 2-ethoxymethyl-3-(5-nitro-2-furyl) acyloyl chloride with amino compounds namely 5-amino-3, 4-dimethyl isoxazole, sulfamonomethoxazole, d-2-amino-1-butanol, hydroxylamine hydrochloride, semicarbazide hydrochloride, thiosemicarbazide, and p, p'-diaminodiphenylsulfone, respectively. The seven synthesized compounds were 2-ethoxymethyl-3-(5-nitro-2-furyl) acryl-5-amino-3, 4-dimethylisoxazoleamide [VII], $N^4-[2-ethoxymethyl\;3-methyl\;(5-nitro-2-furyl)\;acryl]-N^1-(5-methyl-3-isoxazolyl)$ sulfanilamide [VIII], 2-ethoxyl-3-(5-nitro-2-furyl) acrylsemicarbazide [X], 2-ethoxymethyl-3-(5-nitro-2-furyl) acrylthiosemicarbazide [XI], 2-ethoxymethyl-3-(5-nitro-2-furyl) acryl-d-2-amino-1-butanolamide [XII], and 4, 4'-di[2-ethoxymethyl-3-(5-nitro-2-furyl) acryl-amido] diphenylsulfone [XIII]. These compounds, with exception of the compound XIII, showed generally effective antibacterial activity, especially in the following instances. Compound VII was shown to be effective against Bacillus subtilis ATCC 6633 compound VIII, against Bacillus cereus var. Mycoides ATCC 1778, and compound XII, against both Proteus vuglaris and Saccharomyces cerevisiae ATCC 9763.

• 수산해양기술연구
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• 제32권1호
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• pp.67-77
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• 1996

The heat transfer performance of R - 11 vapor condensing on integral fin tubes has been studied using fin tubes having the fin density from 748 to 1654 fins per meter. Electric heater supplied heat energy to the boiler to generate R - 11 vapor over the range of 25-60W. Condensation rates of each tubes were tested under the condition of cooling water flow rate from 400l/h to 2500l/h. For the seven fin tubes tested, the best performance has been obtained with a tube having a fin density of 1417fpm and a fin height of 1.3mm. This tube has yielded a maximum value of the heat transfer coefficient of 16500W/$m_2$K, at a vapor to wall temperature difference of 3K. Experimental results of integral fin tubes have been compared with available predictive models such as Beatty - Katz's analysis, Webb's analysis, Sukhatme's analysis and Rudy's empirical relation. The experimental results were shown to be in good agreement with that of the Sukhatme's analysis.

• 설비공학논문집
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• 제10권6호
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• pp.732-742
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• 1998

Prediction method for heat transfer coefficients in a horizontal smooth tube with forced convection condensation is proposed. In this paper, the analogy between momentum and heat transfer was applied to an annular flow regime and the logarithmic velocity distribution is applied to describe the velocity profile within the liquid film. Prediction results are compared with those of experimental ones. The test refrigerants are R113, R22, R134a, R407C(R33/R125/R134a, 23/25/52 wt%), R410A(R32/R125, 50/50 wt%) and R134a＋R123(R134a/R123, 85.5/14.5 wt%) which are used under operating conditions in a condenser of air-conditioner. The proposed prediction method shows good agreement with experimental data within$\pm 30%$ for pure refrigerants. For the mixture refrigerants including the ternary mixture refrigerant R407C, condensation heat transfer from this study are higher than those from experiments. By correcting the constant in two-phase frictional multiplier, the predicated heat transfer coefficients become similar to the experimental results.

• 한국컴퓨터정보학회논문지
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• 제7권4호
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• pp.108-114
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• 2002

국어의 로마자 표기법 기본원칙을 모르더라도 웹 상에서 한글단어, 문장, 문서를 문자열(String)로 입력받아 국어의 로마자 표기 자동변환이 가능하게 설계 및 구현하였다. 특히, 표음 중심의 전사(Transcription) 표기법의 기계적 변환을 위해 알고리즘(algorithm)화된 음운법칙을 적용하여 소리글자로 자동 변환 후 정부 표준안인 국어 로마자 표기법 테이블에서 대응 글자를 참조하여 기계화 코드 변환이 가능토록 자동변환 알고리즘 설계하였으며, 유니코드(Unicode)와 아스키(ASCII)테이블에서 잘 쓰이지 않는 코드를 반달표(ˇ)와 어깻점(')등 특수부호로 할당하여 글꼴을 제작하였다. 또한 예외어 사전관리를 통한 예외 처리 문제에 대한 해결 방안을 제시하였으며, UML표기와 C++ 언어를 이용하여 사용자 편리성과 구현에 대한 모델을 제안하였다.

• 설비공학논문집
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• 제24권10호
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• pp.711-717
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• 2012

A heat pump dryer for the frozen food needs to preheat the air to a certain temperature where condensation can efficiently occur. In this study, an analysis of a heat pump dryer performance with operating conditions, an analysis of supplying heat with internal and external evaporators and a warm-up experiment with the evaporators have been performed. The results showed that the external evaporator can significantly accelerate the warm-up time of the dryer, so that it can reduce power consumption greatly. The use of the external evaporator is more efficient for higher ambient temperature. In addition, it was found that COP decreases and the range of evaporating pressure for the evaporator becomes narrower as the condensing temperature of the condenser increases.

• 약학회지
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• 제34권6호
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• pp.395-400
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• 1990

The FU-fat conjugates(4a-e) as a prodrug have been synthesized by condensing various fatty acids(1a-e) via isocyanates(2a-e) as carbamoyl group at $N^1-position$ of 5-fluorouracil and their structures characterized. Preliminary testing for their antitumor effect was carried out on leukemia L1210 cells in culture. Most of them(4a-d) like the parent FU exhibited less than 50% inhibition on grouth of the cultrued cells at the concentration of $1\;{\times\;10^{-7}M$. Only a dicarboxylic acid derivative, 4e, showed over 50% inhibition at the same level.

• 대한기계학회논문집B
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• 제25권6호
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• pp.860-867
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• 2001

In this study, condensation heat transfer experiments were conducted with plate and shell heat exchangers(P&SHE) using R-22. An experimental refrigerant loop has been established to measure the condensation heat transfer coefficient of R-22 in a vertical P&SHE. Two vertical counter flow channels were formed in the P&SHE by three plates of geometry with a corrugated trapezoid shape of a chevron angle of 45°. Downflow of the condensing R-22 in one channel releases heat to the cold upflow of water in the other channel. The effect of the refrigerant mass flux, average heat flux, system pressure and vapor quality of R-22 on the measured data were explored in detail. The results indicate that at a higher vapor quality the condensation heat transfer coefficients are significantly higher. A rise in the refrigerant mass flux causes an increase in the h(sub)r. Also, a rise in the average heat flux causes an increase in the h(sub)r. Finally, at a higher system pressure the h(sub)r is found to be slightly lower. Correlation is also provided for the measured heat transfer coefficients in terms of the Nusselt number.

• 대한기계학회논문집
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• 제19권8호
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• pp.2012-2021
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• 1995

An experimental study was performed for the analysis of dynamic characteristics of refrigeration system by controlling the evaporator superheat. Experimental data have been taken utilizing two different devices, thermostatic expansion valve(T.E.V.) and electronic expansion valve(E.E.V.), for the control of the evaporator superheat. The ranges of parameters, such as superheat, mass flow rate of refrigerant and inlet temperature of evaporator were 5-30.deg. C 90-170 kg/h and 10-25.deg. C, respectively. The data taken from the T.E.v.and E.E.v.were discussed with the control of the superheat, pressure drop, refrigerating capacity, compression work, evaporating temperature, condensing temperature and COP affecting performance characteristics of refrigeration system. In case of the refrigerant flow control with T.E..V., the superheat and pressure drop of the evaporator varied periodically, but the control with E.E.V., the parameters were very stable. In E.E.v.control, refrigerating capacity, compression work and evaporating temperature were decreased with increasing superheat, and the highest COP was obtained in the range of superheat from 5.deg. C to 15.deg. C.

• 대한기계학회논문집B
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• 제31권1호
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• pp.91-98
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• 2007

Air-conditioners use a spirally coiled capillary tube as an expansion device to enhance compactness of the unit. However, most empirical correlations in open literature were developed for straight capillary tubes without considering coiled effects on the mass flow rate. The objectives of this study are to investigate the flow characteristics of coiled capillary tubes and to develop a generalized correlation for mass flow rate through coiled capillary tubes. The mass flow rates through the coiled capillary tubes and straight capillary tubes were measured by varying operating conditions and tube geometry. The condensing temperatures varied at 40.5, 47.5 and $54.5^{\circ}C$, and subcoolings altered at 3.5, 6.5 and $11.5^{\circ}C$. The mass flow rates of the coiled capillary tubes decreased by 5 to 16% compared with those of the straight capillary tubes at the same operating conditions. An empirical correlation was developed by introducing equivalent length of capillary tube with non-dimensional parameters for coiled shape. The present correlation predicts the data with average and standard deviations of 0.33% and 3.24%, respectively.