• Journal of Mechanical Science and Technology
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• 제16권3호
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• pp.344-353
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• 2002

A reliable computational heat transfer model has been investigated to define the heat transfer characteristics of a spray column direct contact heat exchanger, which is often utilized in the process involving counterflows for heat and mass transfer operations. Most of the previous studies investigated are one-dimensional unsteady solutions based on rather fragmentary experimental data. Development of a multidimensional numerical model and a computational algorithm are essential to analyze the inherent multidimensional characteristics of a direct contact heat exchanger. The present study has been carried out numerically and establishes a solid simulation algorithm for the operation of a direct contact heat exchanger. Operational and system parameters such as the speed and direction of working fluid droplets at the injection point, and the effects of aspect ratio and void fraction of continuous fluid are examined thoroughly as well to assess their influence on the performance of a spray column.

• 한국분무공학회지
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• 제11권3호
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• pp.155-160
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• 2006

Spray characteristics of charge injected 2-fluid nozzle for non-conducting liquid have been studied. Spray current, specific charge and SMD of diesel have been measured. Spray current and specific charge are proportional to applied voltage. Air flow did not effect on spray current and specific charge. SMD decreases as air flow rate increases and decreases as applied voltage increases additionally. Spray angle increases as applied voltage increases. Fine droplets are obtained by charge injected 2-fluid nozzle without charge loss.

• Geomechanics and Engineering
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• 제13권1호
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• pp.1-23
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• 2017

A coupled liquid-gas-solid three-phase model, linking two numerical codes (TOUGH2/EOS3 and $FLAC^{3D}$), was firstly established and validated by simulating an in-situ air flow test in Essen. Then the coupled model was employed to investigate responses of multiphase flow and soil skeleton deformation to compressed air or freshwater injection using the same simulation conditions in an aquifer of Tianjin, China. The simulation results show that with injecting pressurized fluids, the vertical effective stress in some area decreases owing to the pore pressure increasing, an expansion of soil skeleton appears, and land uplift occurs due to support actions from lower deformed soils. After fluids injection stops, soil deformation decreases overall due to injecting fluids dissipating. With the same applied pressure, changes in multiphase flow and geo-mechanical deformation caused by compressed air injection are relatively greater than those by freshwater injection. Furthermore, the expansion of soil skeleton induced by compressed air injection transfers upward and laterally continuously with time, while during and after freshwater injection, this expansion reaches rapidly a quasi-steady state. These differences induced by two fluids injection are mainly because air could spread upward and laterally easily for its lower density and phase state transition appears for compressed air injection.

• 자원환경지질
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• 제51권3호
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• pp.223-232
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• 2018

본 연구는 이산화탄소 지중저장 과정에서 주입 유체의 온도 변화가 심부 지질구조 내로 주입된 초임계 이산화탄소의 거동과 대체율에 미치는 영향을 정량적으로 규명하기 위하여 초임계 이산화탄소 대체 유체인 헥산을 적용한 마이크로모델 실험을 수행하였다. 본 실험에서는 탈이온수로 포화된 마이크로모델 내부로 헥산의 주입이 개시되는 시점부터 헥산과 공극수의 분포가 평형상태를 이루는 시점까지의 비혼성 대체 과정을 시각적으로 관찰하였다. 실험을 통하여 획득한 이미지는 분석 프로그램을 통하여 전체 공극 구조에 대한 헥산의 대체 면적비를 산정하는데 사용하였으며, 단일 공극 규모에서와 거시적 규모에서의 헥산과 공극수의 거동 및 분포 분석을 통하여 주입 유체의 온도가 비혼성 대체 과정에 미치는 영향을 규명하였다. 주입 유체의 온도 변화에 따른 관측 실험의 결과, 온도가 증가함에 따라 점도, 밀도, 계면장력 등과 같은 유체의 물성 및 공극 구조에 작용하는 모관압의 변화로 인하여 헥산의 대체 면적비는 감소하는 경향을 나타내었다. 이러한 실험 결과는 효율적인 이산화탄소 지중저장을 수행하기 위해서는 이산화탄소 주입이 이루어지는 심부 지질구조의 환경 및 주입 조건에 대한 이해가 필수적임을 시사하였다.

• Journal of Chest Surgery
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• 제29권4호
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• pp.414-419
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• 1996

본 고려대학교 흉부외과 교실에서는 1990년부터 1994년까지 악성흡수로 진단된 81명을 대상으로 악 성흥수의 임상적 인 증상과 원인을 살펴보고, 이 중 64명을 대상으로 화학적 흥막유착술을 실시하여 그 결과를 관찰하였다. 악성흥수의 가장 많은 원인 질환은 남녀 (27세 ∼82세)모두 폐암으로 50 % 의 빈도를 보였고, 가장 흔 한 증상으로는 호흡기 증상이 였다. 화학적 흥막유착술을 실시한 환자의 평균시술횟수는 4회이 였으며, 1달 이내 흥수가 재발하지 않은 단 기간반웅성공율은 92 % 였고, 1달 이상 흥수의 재발이 없었던 장기간 반응성공율은 94 %로 다른 scler- osant보다 높은 성공률을 볼 수 있었다 또한, 화학적흥막유착술을 실시한 후 발생한 부작용은 주로 발 열과 통증으로 이는 비스테로이드성 소염진통제를 투여하여 조절할 수 있었다 악성흥수의 치료에 OK-4)2로 화학적 흥막유착술을 실시하여 좋은 결과를 얻었기에 이에 보고하는 바이다.

• Structural Engineering and Mechanics
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• 제66권4호
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• pp.505-513
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• 2018

Steam flooding is widely used in heavy oil reservoir with coupling effects among the formation temperature change, fluid flow and solid deformation. The effective stress, porosity and permeability in this process can be affected by the multi-physical coupling of thermal, hydraulic and mechanical processes (THM), resulting in a complex interaction of geomechanical effects and multiphase flow in the porous media. Quantification of the state of deformation and stress in the reservoir is therefore essential for the correct prediction of reservoir efficiency and productivity. This paper presents a coupled fluid flow, thermal and geomechanical model employing a program (MATLAB interface code), which was developed to couple conventional reservoir (ECLIPSE) and geomechanical (ABAQUS) simulators for coupled THM processes in multiphase reservoir modeling. In each simulation cycle, time dependent reservoir pressure and temperature fields obtained from three dimensional compositional reservoir models were transferred into finite element reservoir geomechanical models in ABAQUS as multi-phase flow in deforming reservoirs cannot be performed within ABAQUS and new porosity and permeability are obtained using volumetric strains for the next analysis step. Finally, the proposed approach is illustrated on a complex coupled problem related to steam flooding in an oil reservoir. The reservoir coupled study showed that permeability and porosity increase during the injection scenario and increasing rate around injection wells exceed those of other similar comparable cases. Also, during injection, the uplift occurred very fast just above the injection wells resulting in plastic deformation.

• 한국물환경학회지
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• 제37권3호
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• pp.168-174
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• 2021

Mixing is a very important unit in water treatment process. A mechanical stirring method is generally used for mixing, but recently, the use of pressurized water mixing method (pump diffusion flash mixer) has gained interest because it is more advantageous in terms of mixing time, noise, energy consumption, and maintenance. The following conclusions were obtained from the study of pressurized water mixing method by Computational Fluid Dynamics. Firstly, the mixing degree in the pipe increased as the density of water increased. Secondly, even if the relative velocity between flow rate in the pipe and the pressurized water was constant, the mixing degree decreased as the flow velocity in the pipe increased. Thirdly, the stronger the injection energy the higher the mixing degree. It was also found that the mixing degree was greatly affected by the injection velocity as compared to the injection flow amount. Finally, the required energy to achieve 95% mixing degree at the distance of 10 times diameter in big pipes of 500 mm to 3000 mm was 0.3 to 4.5 kJ. The result of this study could be used in the process design of injection with water purification chemicals, such as, ozone, chlorine, and coagulant.

• 한국유체기계학회 논문집
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• 제12권6호
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• pp.13-17
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• 2009

Ejector is an equipment devised for making use of the low pressure occurring from the fast fluid injection and it is a transportation equipment which can obtain vacuum using the kinetic energy of the fluid. This ejector system is, nowadays, widely used for construction machinery, heavy equipments, the cooling and ventilation of electronic devices and for the various fluid transportation and pumps. In this study, it is attempted to perform a numerical analysis and an experiment to find out the characteristics of fluid quantity, velocity and the pressure distribution of the induction pipe by changing the length and the radius ratio of the nozzle of ejector. From the results, it is investigated that the distributions of velocity and pressure of induction pipe attached are changing with the length and the radius ratio of the nozzle. In addition, it is shown that for the small and large ejector, the efficiency is the maximum when the length of the nozzle arrived to the neck of the ejector, however, if it is installed at below or above the neck the efficiency is rather decreased.

• 한국기계가공학회지
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• 제13권1호
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• pp.92-99
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• 2014

An aspherical lens, which resolves several problems with a spherical lens,typically serves asa key part of an optical system. Generally, an aspherical lens is fabricated using a diamond turning machine or by mean of injection molding. However, residual stress and/or tool marks can arise when using a commercial fabricating method such as DTM or injection molding. A polishing process, thus, is commonly used to obtain a high-precision aspherical lens. In this study, a polishing method using MR fluid was applied to minimize several problems, in this case residual stress and the creation of tool marks, during the cutting process. The MR polishing system was developed to polish aspherical lenses. A series of experiments were performed to obtain a very fine surface roughness. PMMA (the lens material for molding) was used as a workpiece, and the gap size, magnetic field intensity, wheel speed and feed rate were selected as the parameters in this study. Finally, a very fine surface roughness of Ra=2.12nm was obtained after MR polishing.

• Water Engineering Research
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• 제2권2호
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• pp.123-138
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• 2001

An injection experiment was carried ut to investigate the pressure domain within which hydromechanical coupling influences considerably the hydrologic behavior of a granite rock mass. The resulting database is used for testing a numerical model dedicated to the analysis of such hydromechanical interactions. These measurements were performed in an open hole section, isolated from shallower zones by a packer set at a depth of 275 m and extending down to 840 m. They consisted in a series of flow meter injection tests, at increasing injection rates. Field results showed that conductive fractures from a dynamic and interdependent network, that individual fracture zones could not be adequately modeled as independent systems, that new fluid intakes zones appeared when pore pressure exceeded the minimum principal stress magnitude in that well, and that pore pressures much larger than this minimum stress could be further supported by the circulated fractures. These characteristics give rise to the question of the influence of the morphology of the natural fracture network in a rock mass under anisotropic stress conditions on the effects of hydromechanical couplings.