• 한국방사선학회논문지
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• 제16권1호
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• pp.61-66
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• 2022

이 연구의 목적은 Ir¹⁹² 선원을 이용한 근접치료에서 물 흡수선량 1 Gy에 대한 광자 에너지플루언스와 질량에너지흡수계수를 유도하는데 있다. Khan이 저술한 방사선치료물리학으로부터 Ir¹⁹² 선원의 감마선 선속에 대한 납의 반가층을 얻었다. 얻어진 납의 반가층으로부터 선감쇠계수와 질량감쇠계수를 산출하였다. 산출된 납의 질량감쇠계수를 NIST의 납의 질량감쇠계수 자료에 대응시켜 일치하는 질량감쇠계수의 광자에너지를 유효에너지로 결정하였다. 결정된 유효에너지를 NIST의 물의 질량에너지흡수계수 자료의 광자에너지에 대응시켜서, 물의 질량에너지흡수계수는 0.03273 cm²/g(32.73 cm²/kg)으로 얻었다. 얻어진 물의 질량에너지흡수계수(32.73 cm²/kg)를 물 흡수선량 1 Gy에 나누어 광자에너지플루언스는 0.03055 J/cm²으로 산출하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제24권3호
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• pp.113-120
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• 2000

On the absorber of absorption chiller/heater, LiBr solution at high concentration is sprinkled on a bundle of horizontal tube cooled by cooling water. In this case, the conditions of LiBr solution and cooling water have an influence on heat/mass transfer coefficient in this system. Therefor it is important to find optimal operation conditions of absorption chiller/heater to save energy. Heat and mass transfer coefficient increased with the increase of solution flow rate, and also heat and mass transfer rate increased but overall heat and mass transfer coefficient decreased by increasing the solution concentration within the experimental range. The superheating of the solution resulted in superior heat transfer character to a state of equilibrium from the point of heat flux and overall heat transfer coefficient.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3044-3050
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• 2021

This study offers a Monte Carlo alternative for computing mass energy absorption coefficients of any material through calculation of photon energy deposited per mass of the sample and the energy flux obtained inside a sample volume. This approach is applied in this study to evaluate mass energy absorption coefficients of some amino acids found in human body at twenty-eight different photon energies between 10 keV and 20 MeV. The simulations involved a pencil beam source modeled to emit a parallel beam of mono-energetic photons toward a 1 mean free path thick sample of rectangular parallelepiped geometry. All the components in the problem geometry were surrounded by a 100 cm vacuum sphere to avoid any interactions in materials other than the absorber itself. The results computed using the Monte Carlo radiation transport packages MCNP6.2 and GAMOS5.1 were checked against the theoretical values available from the tables of XMUDAT database. These comparisons indicate very good agreement and support the conclusion that Monte Carlo technique utilized in this fashion may be used as a computational tool for determining the mass energy absorption coefficients of any material whose data are not available in the literature.

• Korean Chemical Engineering Research
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• 제54권5호
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• pp.648-652
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• 2016

본 연구에서는 구아니딘계 초염기인 1,1,3,3-테트라메틸 구아니딘(TMG)과 에틸렌 글라이콜로 구성된 비수계 흡수제를 충진탑에 적용하여 이산화탄소 흡수특성을 고찰하였다. 흡수탑은 내경이 1 in이고 높이는 0.6 m이며 탑 내부는 $0.16in{\times}0.16in$의 규격을 갖는 다공 충진물로 채웠다. 흡수탑에서의 이산화탄소 제거 효율에 대한 흡수제 농도, 조업온도 등의 영향 뿐 아니라 이들이 물질전달 저항에 미치는 영향을 고찰하였다. 이산화탄소에 대한 TMG의 로딩값은 약 ${\alpha}=1.0mol_{CO2}/mol_{TMG}$에 달하였으며 이산화탄소가 적게 로딩된 흡수제에서는 총괄 물질전달 계수가 TMG의 농도에 비례하였으나 ${\alpha}=0.5$ 이상의 로딩값에서는 총괄 물질전달계수가 오히려 감소하였다. 이는 흡수제의 이산화탄소에 대한 로딩값에 따른 흡수제 점도 증가로 인한 액체상에서의 물질전달 저항 증가로 해석할 수 있다.

• 한국태양에너지학회 논문집
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• 제23권4호
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• pp.45-54
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• 2003

For cooling of double effect absorption heat pump system of solar heating source, analysis of thermodynamic design data has been done to find the property of Libr-water + ethylene Glycol mixture for working fluid by computer simulation. Derived thermodynamic design data, enthalpy based coefficient of performance and flow ratio for possible combinations of operating temperature for water - LiBr and Ethylene Glycol mixture ($H_2O$ : CHO ratio 10:1 by mole) by computer simulation are done. The obtained results, COP and mass flow ratio of the water - lithium bromide - ethylene glycol system, are compared with data for the water-Libr pair solution.

• 설비공학논문집
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• 제6권4호
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• pp.453-462
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• 1994

An unsteady quasi one-dimensional model of momentum, heat and mass transfer in a falling film of a vertical plate absorber which is cooled by air was developed using the integral method. Energy conservation of the absorber wall is considered in the model. The model can predict absorption rate, film thickness and mean velocity as well as concentration and temperature profiles. Predictions of steady state temperature and concentration profiles for LiBr/water system for constant wall temperature condition are in good agreement with the two-dimensional finite difference method solutions. Effects of operating conditions, such as convective heat transfer coefficient between the cooling air and the absorber wall, cooling air temperature and film thickness at inlet, on absorption rate of water vapor into LiBr/water solution were shown.

• 설비공학논문집
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• 제21권12호
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• pp.695-702
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• 2009

Dynamic behavior of Libr-water absorption system using low-temperature hot water was investigated numerically. Thermal-hydraulic model of single-effect/double-lift 100 RT chiller was developed by applying transient conservation equations of total mass, Libr mass, energy and momentum to each component. Transient variations of system properties and transport variables were analysed during start-up operation. Numerical analysis were performed to quantify the effects of bulk concentration and part-load operation on the system performance in terms of cooling capacity, coefficient of performance, and time constant of system. For an absorption chiller considered in the present study, optimum bulk concentration was found to exist, which resulted in the minimum time constant with stable cooling capacity. COP and time constant increased as the load decreased down to 40%, below which the time constant increased abruptly and COP decreased as the load decreased further.

• 설비공학논문집
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• 제16권10호
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• pp.990-998
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• 2004

Dynamic behavior of an ammonia-water absorption system was investigated numerically. Thermal-hydraulic model for a single-effect 3 RT chiller was developed by applying transient conservation equations of total mass, $NH_3$ mass, energy and momentum to each component. Transient variations of system properties and transport variables were analysed during start-up operation. Numerical analyses were performed to quantify the effects of bulk concentration and charging ratio on the system performance in terms of cooling capacity, coefficient of performance, and time constant of system. For an absorption chiller considered in the present study, optimum charging ratio and bulk concentration were to found to exist, which resulted in the maximum cooling capacity and COP. The time constant increased as the charging ratio increased, but decreased with the increase of bulk concentration.

• Korean Chemical Engineering Research
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• 제61권4호
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• pp.555-560
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• 2023

기존 아민 수용액 기반 CO₂ 포집 공정을 산업적으로 적용할 경우 CO₂ 탈거 및 용매 재생에 따른 재생 에너지가 크다는 문제점을 갖고 있다. 본 논문은 CO₂에 대한 높은 흡수 용량과 함께 흡수제에 포함된 물의 조성을 낮춤으로써 재생 에너지를 저감할 수 있는 저수계 흡수제를 제안하였다. 이를 위해 본 연구에서는 디아민인 MAPA (3-methylaminopropylamine)와 함께 물의 일부를 대신하여 물에 비해 CO₂에 대한 물리적 용해도가 높고 비열이 낮은 NMP (N-methyl-2-pyrrolidone)를 흡수제에 도입하였다. 흡수제의 CO₂에 대한 흡수 용량(α_rich)과 순환 흡수 용량(Δα) 및 흡수 속도는 충전탑을 이용하여 측정하였다. 2.5M의 MAPA를 포함한 흡수제를 사용했을 경우 NMP가 10 wt% 포함된 경우에 최대 순환 흡수 용량을 얻을 수 있었다. 총괄물질전달 계수는 NMP의 농도가 증가함에 따라 증가하였다. 그러나 0.5보다 더 높은 CO₂ 로딩 값에서는 NMP의 농도 증가에 따른 물질전달 계수의 증가 폭이 줄어들었다. lean 로딩 값이 낮은 경우에는 점성에 의한 물질전달 저항이 낮아서 NMP 첨가에 따라 총괄 물질전달 계수가 증가하나 로딩 값이 증가함에 따라 흡수제의 점도가 증가하면서 CO₂와 MAPA의 확산도가 낮아지며 이에 따라 총괄 물질전달계수가 급격히 감소하였다.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권2호
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• pp.69-79
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• 2000

Falling film rectification involves simultaneous heat and mass transfer between vapor and solution film. In the present work, the adiabatic rectification process of ammonia-water vapor by the falling solution film on the vertical plate was investigated. The continuity momentum, energy and diffusion equations for the solution film and the vapor mixture were formulated in integral forms and solved numerically, The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer coefficient in each phases were investigated. The stripping of water in vapor mixture occurred near the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer coefficient in falling film.