• Journal of the Korean Institute of Gas
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• 제16권3호
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• pp.35-41
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• 2012

Manifold researches for carbon capture and storage (CCS) have been developed and large scale-carbon capture system can be performed recently. Hence, the technologies for $CO_2$ sequestration or storage become necessary to handle the captured $CO_2$. Among them, enhanced oil recovery using $CO_2$ can be a solution since it guarantees both oil recovery and $CO_2$ sequestration. In this study, the miscible flow of oil and $CO_2$ in porous media is modeled to analyze the effect of enhanced oil recovery and $CO_2$ sequestration. Based on Darcy-Muskat law, the equation is modified to consider miscibility of oil and $CO_2$ and the change of viscosity. Finite volume method is used for numerical modeling. As results, the pressure and oil saturation changes with time can be predicted when oil, water, and $CO_2$ are injected, respectively, and $CO_2$ injection is more efficient than water injection for oil recovery.

• Journal of the Korean Society for Marine Environment & Energy
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• 제19권4호
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• pp.286-296
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• 2016

Offshore CCS technology is to transport and inject $CO_2$ which is captured from the power plant into the saline aquifer or depleted oil-gas fields. The more accumulated injected $CO_2$, the higher reservoir pressure increases. The increment of reservoir pressure make a dramatic change of the operating conditions of transport and injection systems. Therefore, it is necessary to carefully analyze the effect of operating condition variations over the injection period in early design phase. The objective of this study is to simulate and analyze the $CO_2$ behavior in the transport and injection systems over the injection period. The storage reservoir is assumed to be gas field in the East Sea continental shelf. The whole systems were consisted of subsea pipeline, riser, topside and wellbore. Modeling and numerical analysis were carried out using OLGA 2014.1. During the 10 years injection period, the change of temperature, pressure and phase of $CO_2$ in subsea pipelines, riser, topside and wellbore were carefully analyzed. Finally, some design guidelines about compressor at inlet of subsea pipeline, heat exchanger on topside and wellhead control were proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제35권5호
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• pp.1039-1049
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• 2015

The inflow estimation at large multipurpose dam reservoir is carried out by considering the water balance among the discharge, the storage change during unit time interval obtained from the observed water level near dam structure and area-volume curve. This method can be ideal for level pool reservoir but include potential errors when the inflow is influenced by the water level slope due to backwater effects from upstream flood inflows and strong wind induced by typhoon. In addition, the other uncertainties arisen from the storage reduction due to sedimentation after the dam construction and water level noise due to mechanical vibration transmitted from the electric power generator. These uncertainties impedes the accurate hydraulic inflow measurement requiring exquisite hydrometric data arrangement for reservoir waterbody. In this study, the distributed hydrologic model using UBC-3P boundary setting was applied and its feasibility was evaluated. Finally, the modeling performance has been verified since the calculated determination coefficient has been in between 0.96 to 0.99 after comparing with observed peak inflow and total inflow at Namgang dam reservoir.

• Journal of the Korean Institute of Gas
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• 제20권1호
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• pp.13-22
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• 2016

This paper presents development of an appropriate procedure and flow chart to analyze shale gas production data obtained from a multi-fractured horizontal well according to flow characteristics in order to calculate an estimated ultimate recovery. Also, the technical considerations were proposed when a rate transient analysis was performed with field production data occurred to only $1^{st}$ transient flow. If production data show the $1^{st}$ transient flow from log-log and square root time plot analysis, production forecasting must be performed by applying different method as before and after of the end of $1^{st}$ linear flow. It is estimated by an area of stimulated reservoir volume which can be calculated from analysis results of micro-seismic data. If there are no bottomhole pressure data or micro-seismic data, an empirical decline curve method can be used to forecast production performance. If production period is relatively short, an accuracy of production data analysis could be improved by analyzing except the early production data, if it is necessary, after evaluating appropriation with near well data. Also, because over- or under-estimation for stimulated reservoir volume could take place according to analysis method or analyzer's own mind, it is necessary to recalculate it with fracture modeling, reservoir simulation and rate transient analysis, if it is necessary, after adequacy evaluation for fracture stage, injection volume of fracture fluid and productivity of producers.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.149-153
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• 2009

Physics-based distributed rainfall-runoff models are now commonly used in a variety of hydrologic applications such as to estimate flooding, water pollutant transport, sedimentation yield and so on. Moreover, it is not surprising that GIS has become an integral part of hydrologic research since this technology offers abundant information about spatial heterogeneity for both model parameters and input data that control hydrological processes. This study presents the development of a distributed rainfall-runoff prediction system for the Guem river basin ($9,835km^2$) using an Object-oriented Hydrological Modeling System (OHyMoS). We developed three types of element modules: Slope Runoff Module (SRM), Channel Routing Module (CRM), and Dam Reservoir Module (DRM) and then incorporated them systemically into a catchment modeling system under the OHyMoS. The study basin delineated by the 250m DEM (resampled from SRTM90) was divided into 14 midsize catchments and 80 sub-catchments where correspond to the WAMIS digital map. Each sub-catchment was represented by rectangular slope and channel components; water flows among these components were simulated by both SRM and CRM. In addition, outflows of two multi-purpose dams: Yongdam and Daechung dams were calculated by DRM reflecting decision makers' opinions. Therefore, the Guem river basin rainfall-runoff modeling system can provide not only each sub-catchment outflow but also dam inand outflow at one hour (or less) time step such that users can obtain comprehensive hydrological information readily for the effective and efficient flood control during a flood season.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.1658-1662
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• 2009

최근 들어 기후 변화로 인한 이상 강우 현상과 기록적인 집중 강우로 탁수 발생의 빈도와 강도가 증가하고, 탁수의 장기간 하류 방류로 인해 경제적인 피해가 발생할 뿐만 아니라 환경적으로도 중요한 문제로 대두되고 있다. 저수지로 유입된 탁수의 시공간적 분포 예측 결과의 신뢰도는 탁수 밀도류 해석의 정확도에 가장 큰 영향을 받으므로 유입 하천수의 밀도 거동에 대한 정확한 해석이 필요하다. 따라서 탁수의 거동해석은 수리 및 수질의 연동 모의(Coupled modeling)가 필수적이다. 본 연구의 목적은 수리 및 수질의 연동 해석이 가능한 2차원 횡 방향 평균 모형(CE-QUAL-W2)을 소양호에 구축하고, 기록적인 강우 사상을 보인 2006년 수문조건에서의 모형의 적용성과 한계점을 평가하는데 있다. 구축한 소양호 탁수 예측 모델을 2006년 탁수사상에 적용한 결과, 홍수 사상으로 이중 첨두 유량이 발생한 후 저수지 내에서 중층 밀도류와 바닥밀도류의 두 가지 밀도류 형태가 혼재하여 진행되는 현상이 적절히 모의되었다. 하지만, 저수지내에서 측정한 탁수 수괴(plume)의 시공간적 수직분포(profiles)는 모의결과와 다소 편차를 보였으며, 특히 저수지 바닥 인근에서 모델은 실측값을 과대평가 하였다. 오차의 원인은 모델 입력 자료의 불확실성과 수치모델의 불확실성으로 판단된다. 따라서 향후 탁수 거동 모델링과정의 불확실성을 최소화하고 모의결과의 신뢰도를 개선하기 위해서 극한탁수 사상에서 발생하는 수리학적 현상과 SS 입자 동력학에 대한 이론적 연구와 입력 자료의 정확한 산정을 위한 현장 실험이 필요하다.

• Fire Science and Engineering
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• 제18권4호
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• pp.103-109
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• 2004

The risk of underground space become an important issue of life safety thought the Taeku subway line Accident. It is essential to study of smoke control screen to minimize the damage of human life because of smoke passage and passenger evacuation routes are on the same vertical and dispersion movement. The Fire modeling result shows the effect of fire control screen can save the evacuation time about 2-2.5 times compare to existing the system However, The designs of fire control screen need to be complied with smoke control ventilation system to present optimum design and the position of installation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.32-35
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• 2006

The validation of a groundwater source heat pump system installation site is estimated by bydrogeothermic model ing. The hydraulic characteristics of the aquifer system is evaluated from pumping and recovery tests. In addition, the temperature distribution by the pumping and the injection of groundwater, and water level fluctuations are simulated by numerical modeling. The total cooling and heating load for the building is designed as 120RT(refrigeration ton) and the ground water source heat pump system covers 50RT as a subsidiary system The scenario of heat pump operation is organized as pumping and inject ion of groundwater that is performed for 8 hours per day in cooling mode for 90 days during the summer season The heat transfer by the injected warm water is limited near the inject ion wells in the simulated temperature distribution. The reason is that the given operation time is too short to expect broad thermal diffusion in large volume of the aquifer in the simulation time The simulated groundwater level and temperature distribution can be used as important data to develope an energy effective pumping and injection well system. Also it will be very useful to evaluate the hydraulic capacity of a target groundwater reservoir.

• Journal of the Korean Solar Energy Society
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• 제29권6호
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• pp.1-13
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• 2009

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model and compares both methods using Bode plots. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제9권3호
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• pp.343-353
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• 1997

This paper presents a theoretical model for predicting transient behaviors during storage process of the cool storage system using the R141b clathrate. Introduction of the lumped capacitance method along with a brine reservoir having large thermal capacity yields a set of simplified energy equations. Based on the Arrhenius equation and the known experimental findings, the formation rate of clathrate for which the degree of subcooling is properly accounted is newly developed. An effective nondimensionalization of the model equations facilitates the closure of modeling as well as parametric study. Calculated results for a specific case not only simulate a typical pattern of temperautre variation in the tank successfully, but also agree reasonably well with available data. The effect of each characteristic parameter on the system performance is also investigated. It is revealed that the dominant among relevant parameters are the activation energy of reaction, the degree of subcoling and the initial mass fraction of refrigerant. Finally, the uncertainty associated with modeling of the shaft work variation appears to need further studies.