• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.782-791
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• 1998

This paper presents a computer simulation of five types of triple effect absorption cycles employ-ing the refrigerant absorbent combinations of NH3/LiNO3 low-pressure type NH3/LiNO3+H2O/LiBr binary two-stage type series flow cycle and two types of parallel flow cycle for H2O/LiBr. The absorption systems is investigated through cycle simulation to obtain the system characteristics with the cooling water inlet temperature approach temperature of absorber loss temperature of absorber and chilled water outlet temperature. The most important characteristic temperature of absorber and chilled water outlet temperature. The most important characteristic of NH3/LiNO3 low-pressure type and a NH3/LINO3+H2O/LiBr binary two-stage type is that it obtains a coefficient of performance higher than the sum of the performance coefficients of its part operating independently. As a result of this analysis the optimum designs and operating conditions were determined based on the operating conditions and the coefficient of performance.

• 태양에너지
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• 제9권3호
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• pp.73-80
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• 1989

This paper presents as assessment based on steady-state thermodynamic analysis and computer modeling of a double effect generation absorption heating cycle for solar air-conditioning to find operating temperature ranges. The influences of component temperatures on the heating coefficients of performance and mass flow ratio have been investigated to obtain optimum operating conditions for the proposed air conditioning system. And the single and double effect absorption cycles are compared with each other over the same range of temperatures.

• 한국태양에너지학회 논문집
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• 제34권5호
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• pp.65-72
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• 2014

In this paper, the water-based Ag nanofluids are synthesized by the chemical reduction method and their extinction coefficients are measured by an in-house developed measurement device. The Ag nanofluids are manufactured by the chemical reduction method with the mixing of silver nitrate ($AgNO_3$) and sodium borohydride ($NaBH_4$) in an aqueous solution of polyvinyl pyrrolidone (PVP). The extinction coefficients of Ag nanofluids are measured by means of the in-house developed apparatus at a wavelength of 632.8nm according to the particle volume fractions. The results show that the extinction coefficient of water-based Ag nanofluids increases with the increase of nanoparticle concentrations. Finally, the temperature field and efficiency of direct absorption solar collector (DASC) are analytically estimated based on the measured extinction coefficient of water-based Ag nanofluids. The results indicate that the direct absorption solar collectors using nanofluids have the feasibility to improve the efficiency of conventional flat-plate solar collectors without using an absorber plate.

• 한국태양에너지학회 논문집
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• 제27권3호
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• pp.87-94
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• 2007

In this paper, with water-LiCl-$CaCl_2-Zn(NO_3)_2$ mixture which utilizes solar energy at the evaporator heat source, a thermodynamic analysis was performed to provide design data for a double-effect absorption heating system. A comparative study of the water-LiCl-$CaCl_2-Zn(NO_3)_2$ mixture against the water-LiBr pair was conducted by a computer simulation. The computer simulation is based on mass, material and heat balance equations for each part of the system. Coefficients of performance and flow ratios for effects of different operating temperatures are investigated. It is found that the heating COP is higher for the water-LiCl-$CaCl_2-Zn(NO_3)_2$ mixture than for the water-LiBr pair, and FR is lower for the former.

• 한국태양에너지학회 논문집
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• 제26권4호
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• pp.73-81
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• 2006

In this paper, with water-LiBr-LiSCN mixture which utilizes solar energy as mid temperature range evaporator heat source, a thermodynamic analysis was performed to provide design data for a double-effect absorption heating system. A comparative study of the water-LiBr-LiSCN mixture against the water-LiBr pair was conducted by a computer simulation. The computer simulation is based on mass, material and heat balance equations for each part of the system. Coefficients of performance and flow ratios for effects of different operating temperatures are investigated. It is found that the heating COP is higher for the water-LiBr-LiSCN mixture than for the water-LiBr pair, and FR is lower for the former.

• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.581-589
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• 2003

Film absorption involves simultaneous heat and mass transfer in the gas-liquid system. While the non-absorbable gas does not participate directly In the absorption process. its pretence does affect the overall heat and mass transfer. An experimental study was performed to investigate the heat and mass transfer characteristics of LiBr-H$_2$O solution flow ing over 6-row horizontal tubes with the water vapor absorption in the pretence of non-absorbable gases. The volumetric concentration of non-absorbable gas, air, was varied from 0.17 to 10.0%. The combined effects of the solution flow rate and its concentration on the heat and mass transfer coefficients were also examined. The presence of 2％ volumetric concentration of air resulted in a 25% reduction in the Nusselt number and 41% reduction in the Sherwood number Optimum film Reynolds number was found to exist at which the heat and mass transfer reach their maximum value independent of air contents. Reduced Nusselt and Sherwood numbers. defined as the ratio of Nusselt and Sherwood numbers at given non-absorbable gas content to that with pure water vapor, were correlated to account for the reduction in the heat and mass transfer due to non-absorbable gases in a falling film absorption process.

• 설비공학논문집
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• 제5권4호
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• pp.257-264
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• 1993

This is the second report of a three part study on the absorption and heat transfer characteristics of absorber, the correlation of refrigerating capacity and heating capacity. The 2nd report deals with the heat transfer characteristics of a vertical falling film type absorber of inner copper tube. The solute is LiBr-Water solution(60wt%) and the solvent is water vapor. The film Reynoles numbers are varied in the range of 35~130. The states of LiBr solution at the top of absorber are supercooled liquid and superheated liquid. The results are summarized as follows ; Heat transfer results reveal that for the absorption of falling film, the state of LiBr solution appears to be influential in determining the heat transfer. Thus, for the state of supercooled liquid, heat transfer coefficient decreases with increasing the film Reynolds number, but in the condition of superheated liquid, it increases conversely. The mass transfer coefficients that were presented in the 1st.report and heat transfer coefficients of this paper are presented as the dimensionless correlation. The optimum water flowrate which brings about maximum value of heat flux in the film exists, and that increases with increasing the cooling water temperature.

• 한국해양공학회지
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• 제14권2호
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• pp.1-6
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• 2000

Wave energy absorption by a flap equipped with a harbor in a water of finite depth is studied. The wave potential is calculated by a hybrid integral equation consisting of Green integral equations associated with Rankine and Kelvin Green functions. The absorbed wave energy is calculated by both the near-field and far-field methods. The present methods can be used for the design of a flap-harbor wave energy absorber since the numerical results by the two methods are in good agreement.

• Korean Chemical Engineering Research
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• 제43권1호
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• pp.161-169
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• 2005

PVDF(polyvinylidenefluoride)중공사막 접촉기를 이용한 이산화탄소의 흡수에 관한 수치모사 및 실험을 수행하였다. 흡수제로는 물 또는 모노에탄올아민(monoethanolamine, MEA) 수용액을 사용하였다. 수치모사결과, 막접촉기에서의 이산화탄소의 농도분포는 MEA 수용액을 흡수제로 사용하였을 경우가 물을 흡수제로 사용하였을 경우보다 흡수제 공급속도의 영향을 덜 받았으며, 이산화탄소의 흡수속도 및 물질전달계수는 MEA의 농도가 증가할수록 증가하였다. 실험을 통하여 얻은 이산화탄소의 물질전달계수를 수치모사결과 및 이론치와 비교한 결과, 물을 흡수제로 사용하였을 경우 물질전달계수는 실험값과 수치모사결과, 이론값이 모두 잘 일치하였다. 반면에 MEA 수용액을 흡수제로 사용하였을 경우에는 수치모사결과와 이론값은 잘 일치하였으나, 실험값은 플라즈마로 처리한 경우와 처리하지 않은 경우 모두 수치모사 결과보다 낮은 값을 나타내었다. 그러나 막접촉기에 사용된 중공사막의 내구성은 플라즈마로 처리시킨 막이 플라즈마처리를 수행하지 않은 막보다 우수하였다.

• 약학회지
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• 제34권2호
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• pp.126-132
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• 1990

To enhance the activity of ibuprofen, amides of ibuprofen, 1-piperazinyl-2-(4-isobutylphenyl)propionamide(Ibu-P.A.) and 1-(4-methylpiperazinyl)-2-(4-isobutylphenyl)propionamide (Ibu-M.P.), were synthesized and the pharmaceutical properties and the pharmacological activities of the amides were studied. The lipid:water partition coefficients and pKa values were examined in vitro, and the antiinflammatory effect, analgesic effects, acute toxicity, and intestinal absorption were studied for the amides and compared with ibuprofen in vivo. The results are summarized as belows; 1) The lipid:water partition coefficients of Ibu-M.P. were higher than those of ibuprofen. 2) The calculated pKa values of ibuprofen and Ibu-M.P. were 5.49 and 8.66, respectively. 3) The antiinflammatory effects of ibuprofen, Ibu-P.A., and Ibu-M.P. were same intensity, but the duration of the effects of Ibu-P.A. and Ibu-M.P. were longer than that of ibuprofen. 4) The analgesic effect of Ibu-M.P. was more potent than those of ibuprofen and Ibu-P.A. in the acetic acid-induced writhing test. 5) The $LD_{50}$ was 495 mg/kg for ibuprofen, 187 mg/kg for Ibu-M.P., and over 1250 mg/kg for Ibu-P.A.. 6) The absorption rate constants(k) and half-life($t_{1/2}$) were 0.74($hr^{-1}$) and 0.94(hr) for ibuprofen, and 0.72 ($hr^{-1}$) and 0.96 (hr) respectively for Ibu-M.P..