• 기술사
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• 제27권6호
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• pp.72-84
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• 1994

This is about an environmental study of groundwater interference by hydrodynamic dispersion between the well A and well C in Dongsam-dong, the Yeongdo Island, Pusan, Korea. The groundwater in the study wells come from the fracture zones deeply seated in welded lapilli rhyodacitic tuff of the Late Cretaceous Yucheon Group. The boring depth at the well A is 190 meters, and the optimal pumping rate of the well A is about 100 cubic meters per day therein. The fractured aquifers in impermeable welded tuff show the conjugate fracturing type and are of anisotropic. The aquifers along two fracture zones in the well A are 80 and 100 meters in depth, respectively. It is not suggested that those fractured aquifers are simply connected between the well A and C. The sea level fluctuation by ebb and high tides in a day is not effective to the groundwater table in the well A. The pumping for 15 days at the well A doesn't give rise to any changes of the groundwater levels in the neighbor well C. The radius of influence of the well A is measured as less than 200 meters. The measuring electric conductivity for the test of salt tracer doesn't testify any relationship between the well A and the well C. There is the main difference between the well A and the well C on the basis of the water analysis of those wells. the well A is located in the high content zone of salt much over the standard value for drinking, whereas the other wells B. C. D are in the low content area of salt below the standard value. It is elucidated for the high content zone of salt in Yeongdo around the well A to have been uplifted over 20 meters.

• 한국추진공학회지
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• 제18권1호
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• pp.33-41
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• 2014

초음속 터빈에서는 동익 유로에서의 질식 가능성을 줄이며, 설계 압력비를 구현할 수 있도록 한다. 하지만 동익 오버랩을 적용하면, 펌핑손실, 확산손실 등의 추가적인 손실이 동반된다. 따라서 터빈성능을 극대화하기 위한 최적 오버랩 형상을 찾기 위해 근사최적화 기법을 적용하였다. 설계변수는 동익 오버랩의 형상변수이다. 최적설계 결과, 기준모델 대비 팁 누설유량은 약 50% 감소하였으며, 정효율은 약 4% 증가하였다. 팁 오버랩 크기가 성능에 미치는 영향이 크게 나타난 반면, 허브 오버랩 크기가 성능에 미치는 영향은 작게 나타났다.

• 대한지하수환경학회지
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• 제7권3호
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• pp.103-115
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• 2000

갈색 침전물의 생성은 우리나라 지하수의 개발 및 공급에 있어 흔히 발생하는 문제 중의 하나인데, 이에 따라 색도, 맛, 탁도 및 용존 철 함량 등의 항목에 있어 먹는 물 수질 기준을 초과하게 되고, 물 공급 시스템에 스케일링의 문제를 야기하게 된다. 경기도 파주 지역 지하수의 경우에도 양수 후 몇 시간 내에 갈색 침전물이 형성되어 수질을 악화시키고 있다. 본 연구에서는 지하수의 탁도를 유발하는 원인과 지화학적 반응 경로를 이해하고자, 평형열역학 및 반응속도론적 접근을 통하여 갈색 침전물의 형성과정을 파악하였다. 본 연구결과는 침전물의 형성을 최소화하기 위한 적정 양수 기법은 물론 수질 향상을 위한 최적 수처리 기법을 설계하는데 있어 중요한 자료로 활용될 것이다. 파주 지역의 암반 지하수는 물/암석(편마암)반응에 의해 Ca-$HCO_3$형의 수질 특성을 보인다. SEM-EDS 및 XRD 분석 결과, 갈색 침전물은 비정질의 함철 산화물 또는 수산화물로 해석된다. 다양한 공극 크기(6, 4, 1, 0.45, 0.2 $\mu\textrm{m}$)를 갖는 여과지를 이용한 다단계 여과 결과, 이들 침전물은 크기에 있어 대부분 1 내지 0.45$\mu\textrm{m}$의 입도를 갖는 콜로이드 형태이지만, 질량 분포로 볼 때는 1 내지 6$\mu\textrm{m}$범위가 우세함(총 질량의 약 81%)을 알 수 있다. 다량의 용존 철(II)은 지하수 유동 중에 철 함량이 높은(최대 3wt.%) 단층 파쇄암 내의 녹니석(clinochore)의 용해로부터 기원하는 것으로 판단된다. PHREEQC 프로그램을 이용한 포화지수 계산 및 pH-Eh 관계도에 대한 검토 결과, 침전물은 함철 수산화물임이 확인되며, 환원 조건에 있던 심부 지하수가 양수에 의해 산소에 노출되면서 화학성 변화(특히, 산화)에 의하여 침전함을 알 수 있다. 양수 이후의 시간 경과와 더불어 양수된 지하수의 pH, DO, 알칼리도는 점차 감소하며. 탁도는 증가하다가 일정 시간 경과 후 감소하는 경향을 보인다. 양수 이후의 경과 시간에 따른 용존 철(II)의 농도 감소율(즉, 반응 속도)은 Fe(II)=10.l exp(-0.0009t)로 표현된다. 따라서 갈색 침전물의 생성 반응은 양수 및 양수 후 저장 과정 중에 산소의 유입에 따른 산화 반응에 기인하며, 그 반응은 시간, 산소분압 및 pH에 의존함을 알 수 있다. 탁도를 제거하여 음용 가능한 수질을 확보하기 위해서는, 충분한 시간 동안 충분한 크기를 갖는 탱크 내에서의 다단계 저장 및 폭기를 거친 이후에 응집된 침전물에 대한 여과가 제안된다. 이때, 비용 절감 차원에서 상이한 입도 조건에서의 다단계 여과가 효과적일 것으로 생각된다. 한편, 개발 관정 내에서의 스케일링을 최소화하기 위해서는 심부 지하수로 산소가 풍부한 천층 지하수가 유입되는 과정을 최소화할 필요가 있다. 이를 위해서는 적정 채수량 범위 내에서의 지속적인 양수가 효과적일 것이다. 아울러, 산소가 풍부한 천층 지하수의 채수를 위한 별도의 관정 설치도 고려할 수 있을 것이다.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.128-135
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• 2008

EGR(exhaust gas recirculation) is considered as a most effective method to reduce the NOx emissions. But high EGR tolerance is always pursued not only for its advantages of the pumping loss reduction and fuel economy benefit in Gasoline-Hybrid engine. However, the occurrence of excessive cyclic variation with high EGR normally prevents substantial fuel economy improvements from being achieved in practice. Therefore, the optimum EGR rate should be carefully determined in order to achieve low fuel consumption and low exhaust emission. In this study, 2 liters gasoline engine with E-EGR system was used to investigate the effects of EGR on fuel efficiency, combustion stability, engine performance and exhaust emissions. With optimal EGR rates, the fuel consumption was improved by 4%. This improvement was achieved while a reduction in NOx emissions of 75% was accomplished. Increase of EGR gas temperature causes the charge air temperature to affect the knock phenomenon and moreover, the EGR valve lift changes for the same control signal.

• 한국광학회지
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• 제10권2호
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• pp.157-161
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• 1999

실험실에서 제작한 HCP와 IPS를 이용하여 Ti:Sapphire 레이저를 발진시키고 그 특성을 조사하였다. 레이저의 문지방 에너지 1.39kJ로 나타났다. 레이저 효율은 LD-490의 농도 10$\times$10-3Mol/l일 때 가장 높은 효율을 나타내었으며, LD-490의 농도가 낮으면 효율도 감소하는 것으로 나타났다. 레이저의 출력은 5.42 kJ의 입력 에너지에 대해 287mJ이었다. Ar의 방출대와 일치하는 BBQ(bis[2-butyloctyl)oxy]quatephenyl)를 LD-490과 1:1로 혼합하여 에너지 전환제로 사용한 결과 측정한 전구간에 걸쳐 출력 에너지가 증가하였고 문지방 에너지가 LD-490만을 사용할 때 보다 0.22 kJ이 낮아진 1.17 kJ이었다.

• 설비공학논문집
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• 제24권2호
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• pp.183-189
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• 2012

Most of the domestic residential buildings have used the traditional radiant heating system, circulating hot water through the cross-linked polyethylene(PE-X) pipe buried in the floor panel of the heating space. New type of the heating panel was recently developed using heat pipes with double wicks. Some experiments were carried out in this study to verify the thermal characteristics of this heating system at the unit heating space which surrounded by outer space whose temperature of air be maintained scheduled value with time. Through the various experiments with several parameters, such as flow rate, inlet and outlet temperatures of hot water and the heating duration and so on, we found that the floor heating system with heat pipes was able to reduce the pumping power for hot water circulation by 4~31% compared with the conventional panel heating system using PE-X pipe. These results could be used for optimal design and efficient operation of the heating system as well as improvement of thermal comfort.

• 한국가시화정보학회지
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• 제22권1호
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• pp.79-84
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• 2024

As microchips' degree of integration is getting higher, its cooling problem becomes important more than ever. One of the promising methods is using fractal microchannel heat sink by mimicking nature's Murray networks. However, most of the related works have been progressed only by numerical analysis. Perhaps such lack of direct experimental studies is due to the technical difficulty of the temperature and heat flux measurement in complex geometric channels. Here, we demonstrate the direct visualization of in situ temperature profile in a fractal microchannel heat sink. By using the temperature-sensitive fluorescent dye and a transparent Polydimethylsiloxane window, we can map temperature profiles in silicon-based fractal heat sinks with various fractal scale factors (a=1.5-3.5). Then, heat transfer rates and pressure drops under a fixed flow rate were estimated to optimize hydrodynamic and thermal characteristics. Through this experiment, we found out that the optimal factor is a=1.75, given that the differences in heat transfer among the devices are marginal when compared to the variances in pumping power. This work is expected to contribute to the development of high-performance, high-efficiency thermal management systems required in various industrial fields.

• 한국지하수토양환경학회지:지하수토양환경
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• 제22권5호
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• pp.23-29
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• 2017

This study was conducted to evaluate performance of geothermal heat exchanger (GHE) in the combined well and open-closed loops geothermal (CWG) systems. The CWG systems were designed to combine open loop geothermal heat pumps and closed loop geothermal heat pumps for high energy efficiency. GHE of the CWG systems could be installed at pumping wells for agricultural usage. To get optimal heat exchange capacity of GHE of the CWG systems, 4 GHEs with various materials and apertures were tested at laboratory scale. Polyethylene (PE) and stainless steel (STS) were selected as GHE materials. The maximum heat exchange capacity of GHEs were estimated to be in the range of 33.0~104 kcal/min. The heat exchange capacity of STS GHEs was 2.4~3.2 times higher than that of PE GHE. The optimal cross section area of GHE and flow rate of circulating water of GHE were estimated to be $2,500mm^2$ and 113 L/min, respectively. For more complicated GHE of the CWG systems, it is necessary to evaluate GHEs at various scales.

• KIEAE Journal
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• 제17권3호
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• pp.119-124
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• 2017

Purpose: Groundwater heat pump (GWHP) system has high coefficient of performance than conventional air-source heat pump system and closed-loop type geothermal system. However, there is problem in long-term operation that groundwater raise at the diffusion well and reduced at the supply well. Therefore, it is necessary to accurately predict the groundwater flow, groundwater movement and control the groundwater level in the wells. In this research, in consideration of hydrogeological characteristic, groundwater level and groundwater movement were conducted analysis in order to develop the optimal design method of the two-well system using the pairing pipe. Method: For the optimum design of the two-well system, this research focused on the design method of the pairing pipe in the simulation model. Especially, in order to control the groundwater level in wells, pairing pipe between the supply well and diffusion well was developed and the groundwater level during the system operation was analyzed by the numerical simulation. Result: As the result of simulation, the groundwater level increased to -2.65m even in the condition of low hydraulic conductivity and high pumping flow rate. Consequently, it was found that the developed system can be operated stably.

• Design & Manufacturing
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• 제15권4호
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• pp.43-50
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• 2021

Pump-cap is a device for discharging the contents stored inside a container to the outside of the container by a simple operation by a certain amount. In particular, in recent years, as the number of cosmetic products made of functional materials has rapidly increased, the development of convenient containers for functional materials is being actively conducted. Among these, there are a growing number of products that show their efficacy only by mixing two components, so the development of a dual pump cap container is necessary. However, the conventional dual pump cap container has a problem in that it is difficult to implement a quantitative discharge as solutions having different viscosities are used. Therefore, in this study, a discharge port of a dual pump cap that can apply an optimal ratio was designed by analyzing the discharge amount of two components with different viscosities through computational fluid dynamics. Since the discharge amount is affected by the size of the discharge port, the higher the viscosity of the solution, the larger the discharge port should be set. Conversely, the lower the viscosity, the smaller the discharge port should be. Through this, it is possible to dispense a fixed amount of a heterogeneous solution by one pumping, and it is determined that the user's convenience will increase.