• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 하계학술발표대회
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• pp.103-103
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• 2005

• 한국산학기술학회논문지
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• 제20권10호
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• pp.100-106
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• 2019

고농도 과산화수소와 케로신을 추진제로 하는 액체 로켓 엔진을 이용하여 수직형 연소 실험대에 고고도 모사용 디퓨저와 기 검증된 추력 측정 장치를 장착하여 지상 및 고고도 모사 연소 실험 설비를 구축하였으며, 고도에 따른 추력 특성을 고찰하였다. 선행으로 고고도 모사용 디퓨저의 특성 및 시동압력을 검증하기 위하여 1:4.8 스케일로 축소한 디퓨저를 설계 및 제작하였다. 축소형 디퓨저는 질소 가스를 이용하여 cold flow test를 수행하여 성능 및 시동 특성을 확인하였으며, 그 결과 연소 실험용 디퓨저의 성능 안정성과 시동 특성을 확보하였다. 수직형 연소 실험대에 고고도 모사용 디퓨저와 추력 측정 장치를 장착하고, 시스템 저항에 대한 추력 보정식을 도출하였다. 추력 보정식은 실제 연소 실험 전에 수행한 추력 단계별 실험과 진공 단계별 실험을 통하여 도출하였다. 작동 고도가 10km인 노즐을 설계, 제작하여 지상 연소 실험 및 고고도 모사 연소 실험을 수행하여 작동 고도 변화에 따른 추력 특성을 분석하였다. 추력 측정 장치에서 계측한 추력값을 이용하여 실제 추력을 각각의 보정식을 이용하여 계산하였다.

• 설비공학논문집
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• 제10권4호
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• pp.483-494
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• 1998

This study describes the characteristics on impeller discharge flow of a centrifugal compressor with vaneless diffuser. Distorted flow at impeller exit was investigated by measuring of unsteady velocity fluctuation using hot-wire anemometer. As a result, a wake region appears near shroud side and moves to suction side and also to hub side as flow rate decreases. Jet, wake, and their boundary region which can be defined in jet-wake flow model are clearly observed at a high flow rate for the flow coefficient of 0.64, however, as flow rate decreases to the flow coefficient of 0.19, the classification of their regions disappears. Turbulence intensity also increases as flow rate decreases. Measurement error from uncertainty analysis is estimated about 4% at the flow coefficient of 0.19

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1196-1200
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• 2004

Micropump is very useful component in micro/nano fluidics and bioMEMS applications. In this study, a bubble-powered micropump was fabricated and tested. The micropump consists of two-parallel micro line heaters, a pair of nozzle-diffuser flow controller and a 1 mm in diameter, 400 ${\mu}m$ in depth pumping chamber. The two-parallel micro line heaters with 20 ${\mu}m-width$ and 200 ${\mu}m-length$ were fabricated to be embedded in the silicon dioxide layer of a wafer which serves as a base plate for the micropump. The pumping chamber, the pair of nozzle-diffuser unit and microchannels including the liquid inlet and outlet port were fabricated by etching through another silicon wafer. A glass wafer (thickness of $525{\pm}15$ ${\mu}m$) having two holes of inlet and outlet ports of liquid serve as upper plate of the pump. Finally the silicon wafer of the base plate, the silicon wafer of pumping chamber and the glass wafer were aligned and bonded (Si-Si bonding and anodic bonding). A sequential photograph of bubble nucleation, growth and collapse was visualized by CCD camera. Clearly liquid flow through the nozzle during the period of bubble growth and slight back flow of liquid at the end of collapsing period can be seen. The mass flow rate was found to be dependent on the duty ratio and the operation frequency. As duty ratio increases, flow rate decreases gradually when the duty ratio exceeds 60%. Also as the operation frequency increases, the flow rate of the micropump decreases slightly.

• 대한기계학회논문집A
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• 제34권8호
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• pp.1059-1065
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• 2010

본 연구에서는 SMART 원자로의 사류형 원자로냉각재펌프의 축소모형에 대한 수력성능을 예측하기 위하여 설계점을 포함한 다양한 탈설계점에서의 해석을 수행하였다. 계산시간의 효율성을 위하여 임펠러와 디퓨저 각 1개 유로로 이루어진 계산영역을 해석대상으로 선정하였다. 임펠러와 디퓨저간의 정보교환을 위하여 스테이지 기법을 사용하였다. 정상상태 비압축성 유동조건에서 축소모형의 수력성능특성을 파악하기 위하여 해석영역의 입구와 출구에서 압력차를 측정하여 양정, 효율과 축동력을 산출하였다. 수력성능 곡선은 일반적인 사류펌프의 성능특성을 잘 모사하는 것으로 나타났다. 저유량에서의 펌프 내부유동의 복잡한 흐름을 확인 하였다.

• 상하수도학회지
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• 제18권4호
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• pp.437-444
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• 2004

To control algal bloom in reservoirs in Korea, artificial circulation systems have been applied. Diffuser block aeration systems have been increasingly used in Korean reservoirs especially for shallow ones. However, there has been no sound theoretical background for the design and operation of the system. Also there has not been sufficient post-installation studies to validate the effectiveness of the system. As a result, it has been repeatedly reported that the success of the system is not certain. Proper consideration on thermal stratification regimes of reservoirs and flow dynamics induced by bubble plumes are essential elements in design processes of the aeration system. This paper discusses the current methods in the design of diffuser type aeration system and suggests a new design method based on fluid mechanical theory. Example calculations were discussed using observed data of the Yeoncho Dam and it seems that the results represent the current situation successfully.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1186-1190
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• 2003

In this paper, a valveless bubble-actuated fluid micropump was has been developed and its performance was tested. The valveless micropump consists of the lower plate, the middle plate, the upper plate and a resistive heater. The lower plate includes the nozzle-diffuser elements and the double-chamber. Nozzle-diffuser elements and a double-chamber are fabricated on the silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The lower plate also has inlet/outlet channels for fluid flow. The middle plate is made of glass and plays the role of the diaphragm. The chamber in the upper plate is filled with deionized water, and which contacts with the resistive heater. The resistive heater is patterned on a silicon substrate by Ti/Pt sputtering. Three plates and the resister heater are laminated by the aligner and bonded in the anodic bonder. Since the bubble is evaporated and condensed periodically in the chamber, the fluid flows from inlet to outlet with respect to the diffusion effect. In order to avoid backflow, the double chamber system is introduced. Analytical and experimental results show the validity of the developed double-chamber micropump.

• 한국공작기계학회논문집
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• 제17권6호
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• pp.14-22
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• 2008

This study is aimed at suggesting a linear-type diffuser which is excellent in terms of range and elegance like existing diffusers in which amount and direction of wind can be freely controled, out of linear-type diffusers with the highest possibility to be adopted for living space of apartments whose height between floors is not so high and utilizing the linear-type diffuser in design. For the purpose, I examined necessary flow and noise properties of linear-type diffusers. Besides, I evaluated its ventilation capacity for persons in there by applying this in the actual living space. I evaluated features and air blast and found that in time of horizontal and vertical effusion, its T/L ratio is 1-1.5, similar to existing cardioid-type linear diffusers, while in time of slope effusion, it is similar to horizontal effusion in terms of range and it has medium figure in terms of pressure drop and effusion speed, indicating it can provide safe and pleasant indoor environment for persons in there in terms of ventilation.

• 설비공학논문집
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• 제29권3호
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• pp.105-110
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• 2017

Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings. UFAD systems use the underfloor plenum beneath a raised access floor to provide conditioned air through floor diffusers that create a vertical thermal stratification during cooling operations. Thermal stratification has significant effects on energy, indoor air quality, and thermal comfort performance. The purpose of this study was to characterize the influence of a linear bar grille diffuser on thermal stratification in both interior and perimeter zones by developing Gamma-Phi based prediction models. Forty-eight simulations were carried out using a Computational Fluid Dynamics (CFD) technique. The number of diffusers, the air flow supply, internal heat gains, and solar radiations varied among the different cases. Models to predict temperature stratification for the tested linear bar grille diffuser have been developed, which can be directly implemented into dynamic whole-building simulation software such as EnergyPlus.

• 한국추진공학회지
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• 제12권4호
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• pp.16-23
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• 2008

고고도에서 작동하는 로켓의 작동 환경을 지상에서 모사하기 위한 초음속 디퓨져의 연구를 위하여 이론적 접근과 수치적 접근을 수행하였다. 물리적 모델은 축대칭 형상을 갖는 디퓨져, 진공챔버, 로켓모터로 구성하였으며, 유동 발달 측면에서 초음속 디퓨져 작동특성에 관한 연구를 수행하였다. 본 논문은 디퓨져의 시동압력 예측모델, 진공챔버 크기의 효과, 디퓨져 시동을 위한 로켓모터의 최소 시동압력에 대한 연구내용을 수록하였다