• 설비공학논문집
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• 제24권4호
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• pp.297-305
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• 2012

In recent large-scale semiconductor manufacturing clean rooms, the energy consumption of outdoor air conditioning systems to heat, humidify, cool and dehumidify incoming outdoor air represents about 45% of the total air conditioning load required to maintain a clean room environment. Therefore, the energy performance evaluation and analysis of outdoor air conditioning systems is useful for reducing the outdoor air conditioning load for a clean room. In the present study, an experiment was conducted to compare the energy consumption of outdoor air conditioning systems with a simple air washer, an exhaust air heat recovery type air washer and a DCC return water heat recovery type air washer. It was shown from the present lab-scale experiment with an outdoor air flow of 1,000 $m^3/h$ that the exhaust air heat recovery type and DCC return water heat recovery type air washer outdoor air conditioning systems were more energy-efficient for the summer and winter operations than the simple air washer outdoor air conditioning system and furthermore, the DCC return water heat recovery type one was the most energy-efficient in the winter operation.

• Asian Journal of Atmospheric Environment
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• 제10권4호
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• pp.179-189
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• 2016

Here we evaluated the effect of using water retentive pavement or WRP made from fly ash as material for main street in a real city block. We coupled computational fluid dynamics and pavement transport (CFD-PT) model to examine energy balance in the building canopies and ground surface. Two cases of 24 h unsteady analysis were simulated: case 1 where asphalt was used as the pavement material of all ground surfaces and case 2 where WRP was used as main street material. We aim to (1) predict diurnal variation in air temperature, wind speed, ground surface temperature and water content; and (2) compare ground surface energy fluxes. Using the coupled CFD-PT model it was proven that WRP as pavement material for main street can cause a decrease in ground surface temperature. The most significant decrease occurred at 1200 JST when solar radiation was most intense, surface temperature decreased by $13.8^{\circ}C$. This surface temperature decrease also led to cooling of air temperature at 1.5 m above street surface. During this time, air temperature in case 2 decreased by $0.28^{\circ}C$. As the radiation weakens from 1600 JST to 2000 JST, evaporative cooling had also been minimal. Shadow effect, higher albedo and lower thermal conductivity of WRP also contributed to surface temperature decrease. The cooling of ground surface eventually led to air temperature decrease. The degree of air temperature decrease was proportional to the surface temperature decrease. In terms of energy balance, WRP caused a maximum increase in latent heat flux by up to $255W/m^2$ and a decrease in sensible heat flux by up to $465W/m^2$.

• 한국지하수토양환경학회지:지하수토양환경
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• 제15권1호
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• pp.39-49
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• 2010

Drilling at unconsolidated layer can make the aquifer disturbed and reduce a productivity of groundwater well. Surge block and air surging were applied to a pumping well located in Jeungsan-ri, Changnyung-gun, to improve a well efficiency by removing clogging and fine-grained slime. Two experimental log-linear equations, $y_1=-0.1769\;ln(x_1)+0.4960$ and $y_2=-84.3358\;ln(x_2)+512.8162$, were proposed in this site, in which $x_1$ and $x_2$ are the number of surging event, $y_1$ is the amount of slime, and $y_2$ is a recovery time of groundwater level after air surging. Well loss exponent (P) decreased after surging, from 3.422 to 1.439, and the groundwater inflow from aquifer happened in all directions around a well with gradually increasing the homogeneity in a local aquifer's hydraulic property. It was revealed that long-term well development should be done in the pumping well which is located in unconsolidated sediments to increase a well productivity.

• 한국물환경학회지
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• 제36권1호
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• pp.14-28
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• 2020

Future climate change may affect the hydro-thermal and biogeochemical characteristics of dam reservoirs, the most important water resources in Korea. Thus, scientific projection of the impact of climate change on the reservoir environment, factoring uncertainties, is crucial for sustainable water use. The purpose of this study was to predict the future water temperature and stratification structure of the Soyanggang Reservoir in response to a total of 42 scenarios, combining two climate scenarios, seven GCM models, one surface runoff model, and three wind scenarios of hydrodynamic model, and to quantify the uncertainty of each modeling step and scenario. Although there are differences depending on the scenarios, the annual reservoir water temperature tended to rise steadily. In the RCP 4.5 and 8.5 scenarios, the upper water temperature is expected to rise by 0.029 ℃ (±0.012)/year and 0.048 ℃ (±0.014)/year, respectively. These rise rates are correspond to 88.1 % and 85.7 % of the air temperature rise rate. Meanwhile, the lower water temperature is expected to rise by 0.016 ℃ (±0.009)/year and 0.027 ℃ (±0.010)/year, respectively, which is approximately 48.6 % and 46.3 % of the air temperature rise rate. Additionally, as the water temperatures rises, the stratification strength of the reservoir is expected to be stronger, and the number of days when the temperature difference between the upper and lower layers exceeds 5 ℃ increases in the future. As a result of uncertainty quantification, the uncertainty of the GCM models showed the highest contribution with 55.8 %, followed by 30.8 % RCP scenario, and 12.8 % W2 model.

• 한국물환경학회지
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• 제35권2호
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• pp.131-144
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• 2019

Climate Change affects the hydrological cycle in agricultural watersheds through rising air temperature and changing rainfall patterns. Agricultural watersheds in Korea are characterized by extensive paddy fields and intensive water use, a resource that is under stress from the changing climate. This study analyzed the effects of climate change on river flows for Geum Cheon and Eun-San Choen watershed using STREAM, a semi-distributed watershed model. In order to evaluate the performance and improve the reliability of the model, calibration and validation of the model was done for one flow observation point and three reservoir water storage ratio points. Climate change scenarios were based on RCP data provided by the Korea Meteorological Administration (KMA) and bias corrections were done using the Quantile Mapping method to minimize the uncertainties in the results produced by the climate model to the local scale. Because of water mass-balance, evapotranspiration tended to increase steadily with an increase in air temperature, while the increase in RCP 8.5 scenario resulted in higher RCP 4.5 scenario. The increase in evapotranspiration led to a decrease in the river flow, particularly the decrease in the surface runoff. In the paddy agricultural watershed, irrigation water demand is expected to increase despite an increase in rainfall owing to the high evapotranspiration rates occasioned by climate change.

• Journal of Advanced Marine Engineering and Technology
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• 제38권7호
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• pp.814-820
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• 2014

문명의 발전과 도시화, 산업화를 통하여 인류는 의식주의 해결뿐 아니라 더 낳은 생활환경을 추구하였다. 그 결과 냉동 및 공조 분야의 연구와 개발이 활발히 진행되어 왔다. 하지만 인류는 21세기에 들어 상승하는 고유가와 환경문제를 더 이상 간과할 수 없게 되었다. 그 대안으로, 해수의 열원을 이용한 열펌프의 개발이 진행되었다. 본 논문에서는 2010년의 해수와 대기의 온도를 분석하여 열펌프의 국내적용을 위한 성능평가 시뮬레이션을 HYSYS 프로그램을 이용하여 전수식과 전공기식에 적용하였다. 그 결과, 총 평균 성능계수는 전수식에서 3.37 그리고 전공기식에서 3.48을 기록하였다. 이와 같은 결과로 해수열원을 이용한 열펌프 시스템이 국내사용에 적합함을 알 수 있었다.

• 한국물환경학회지
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• 제25권4호
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• pp.547-552
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• 2009

Because of refractory property of light, the travel path of UV light becomes longer than the straight line and shorter solely in water as UV light passes sequentially through air, quartz and water. Note that water significantly absorbs UV light. Hence, UV intensity shall be estimated to be lower when refraction is neglected than it is considered. Reflection is also critical for the design of UV radiation system. While the reflection at the interface of air and quartz is low enough to ignore, it is too high to be ignored at the interface of quartz and water. Assuming constant power, smaller length to width ratio of UV reactor is beneficial and single-lamp system is preferred to multi-lamps. Under the given cross section, optimal lamp positions could be decided. For example of an elliptical reactor with dual lamps, the optimal lamp locations shall be the 1/3 and 2/3 position of the longer axis.

• 해양환경안전학회지
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• 제20권3호
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• pp.312-317
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• 2014

In this paper, the wave run-up height and depression depth around air-water interface-piercing circular cylinder have been numerically studied. The Reynolds Averaged Navier-Stokes equations (RANS) and continuity equations are solved with Reynolds Stress model (RSM) and volume of fluid (VOF) method as turbulence model and free surface modeling, respectively. A commercial Computational Fluid Dynamics (CFD) software "Star-CCM+" has been used for the current simulations. Various Froude numbers ranged from 0.2 to 1.6 are used to investigate the change of air-water interface structures around the cylinder and experimental data and theoretical values by Bernoulli are compared. The present results showed a good agreement with other studies. Kelvin waves behind the cylinder were generated and its wave lengths are longer as Froude numbers increase and they have good agreement with theoretical values. And its angles are smaller with the increase of Froude numbers.

• 자원환경지질
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• 제43권6호
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• pp.565-571
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• 2010

계면활성제를 이용하여 대수층의 특정층에 존재하는 휘발성 오염물질을 선택적으로 제거할 수 있는 새로운 지하수 폭기기술을 개발하였다. 모래가 충진된 실험설 규모의 물리적 모델을 이용하여 이 폭기기술의 효율성을 검증하였다. 모델의 특정깊이(바닥으로부터 약 22 cm)에 일정한 두께로 존재하는 용해된 상태의 톨루엔 플룸을 제거하는 실험을 실시하였으며, 오염물질이 존재하는 영역의 표면장력을 저감하기 위하여 음이온계 계면활성제인 SDBS(Sodium dodecylbenzene sulfonate)를 주입하였다. 또한 비교를 위하여 동일한 조건에서 계면활성제가 주입되지 않은 실험도 실시하였다. 오염영역의 하부로부터 공기로서 폭기한 결과, 계면활성제에 의하여 저감된 표면장력의 효과에 의하여 오염영역에 대한 폭기영향권의 크기가 현저히 증가하였으며 그 결과 70%이상의 톨루엔이 제거되었다. 반면 계면활성제가 주입되지 않은 조건에서는 20%이하의 톨루엔만 제거되었다. 이는 계면활성제에 의하여 표면장력이 낮아져 폭기 과정에서 플룸에 대한 공기주입이 매우 효율적으로 이루어졌으며, 따라서 톨루엔을 포함하는 대수층의 지하수가 공기와의 접촉이 보다 용이해졌음을 의미한다. 이 새로운 방법은 휘발성 유기물질로 오염된 대수층을 복원하는데 유용하게 이용될 수 있을 것으로 기대된다.

• 한국해양환경ㆍ에너지학회지
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• 제13권2호
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• pp.91-98
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• 2010

진동수주형 파력발전장치에서 공기실 내의 수면 변화와 덕트 내 유량의 왕복유동은 시스템의 작동 성능을 결정짓는 매우 중요한 요소이다. 공기실 내의 수면 변화를 고찰하기 위하여 상용 CFD 코드인 Fluent 6.2를 이용하여 구현한 수치조파수조를 사용하였다. 수치조파수조의 지배방정식은 연속방정식과 Reynolds 평균 N-S 방정식이고 자유수면은 Two-phase VOF 기법을 이용하여 추적하였다. 공기실 내의 수면 변화와 공기실 윗부분에 설치된 덕트 내의 왕복유량을 계산하여 고찰하였고, 계산의 정확도를 검증하기 위하여 실험결과와 비교 분석을 수행하였다. 또한 동일한 입사파 조건에서 공기실 - 덕트 시스템의 노즐 비율이 시스템이 미치는 영향을 고찰하여 분석을 하였다.