• 설비공학논문집
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• 제15권5호
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• pp.397-405
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• 2003

Heat and fluid flow in a compressor into which liquid refrigerant is injected for the purpose of reducing discharge gas temperature in a heat pump system has been numerically studied. A mechanistic approach encompassing liquid jet breakup and droplet evaporation has been performed to investigate the effects of liquid injection on the spacial and temporal variation of the gas temperature and pressure inside the compressor cylinder. Various parameters, such as liquid injection mass, time, duration and droplet size, are considered in the present study to elucidate the flow field inside the compressor. As the injection mass is increased, discharge gas temperature is decreased, while the pressure is increased due to the added mass of the injection. For the injected liquid mass corresponding to 15% of the total vapor mass in the cylinder, the discharge gas temperature drops by 22.4 K. It is observed that the droplet size plays a major role in the evaporation rate of the droplets that determines the degree of the discharge temperature drop.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.192-193
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• 2006

In this paper, a co-axial type ozonizer varied with discharge gap was designed and manufactured for investigating (1) discharge characteristics with variation of output voltage power supply, flow rate and gap distance (2) ozone generation and solubility characteristics with variation of flow rate, gap distance and discharge power. Pure oxygen was used as process gas of the co-axial type ozonizer.

• 한국물환경학회지
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• 제27권5호
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• pp.617-624
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• 2011

In order to confirm the creation of the OH radical which influences to RNO bleaching processes, it experimented using laboratory reactor of dielectric barrier discharge plasma (DBDP). The experiments performed in about 4 kind process variables (diameter of ground electrode, diameter of discharge electrode, diameter of quartz tube and effect of air flow rate) which influence to process. In order to examine optimum conditions of design factors as shown in Box-Behnken experiment design, ANOVA analysis was conducted against four factors. The actual RNO removal at optimized conditions under real design constraints were obtained, confirming Box-Behnken results. Optimized conditions under real design constraints were obtained for the highest desirability at 1, 1 mm diameter of ground and discharge electrode, 6 mm diameter of quartz tube and 5.05 L/min air flow rate, respectively.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.800-807
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• 2006

Sea dyke construction is simply defined that the cutting procedure of sea water flow. Sea dyke construction is more difficult than in-land construction because it’s placed on deep seabed and exposed sea wave attack. Especially, the final closure of sea dyke is most dangerous due to the fast velocity of tidal flow. The final closure section is consisted with vast rubble and heavy stone gabion, therefore the discharge velocity at land side of final close section is irregularly and sometime occur the fast discharge velocity. In this study, the seepage model test performed to evaluate seepage behavior with tidal variation of final closure and continuous sea dyke section such as discharge velocity, hydraulic gradient, and phreatic line. Based on the seepage model test results, the maximum discharge velocity of final closure section is 1.7m/sec. Also the local discharge velocity increment and vortex is occurred.

• 한국농공학회논문집
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• 제48권1호
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• pp.27-38
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• 2006

In this study, we developed a program to estimate discharge efficiently considering major hydraulic characteristic including water level, river bed, water slope and roughness coefficient in a natural river. Stream discharge was measured at Gongju gauge station located in the down stream of the Daechung Dam during normal and dry seasons from 2003 to 2004. The developed model was compared with the results from the existing rating curve at T/M gage stations, and was used for runoff analyses. Evaluating the developed river discharge estimation program, it was applied during 1983-2004 that base flow separation method and RRFS (Rainfall Runoff Forecasting System) which is based on SSARR (Streamflow Synthesis And Resevoir Regulation). The result presents the stage-discharge curve creator range at the Gong-ju is overestimated by approximately $10-20\%$, especially at the low stage. It is attributed to the hydraulic characteristics at the study. The discharge simulated by the RRFS and base flow separation, which is calibrated using the measurement at the early spring and late fall season during relatively d]v season, shows the least errors. The coefficient of roughness at Gongju station varied with the high and low water level.

• 한국수자원학회논문집
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• 제37권5호
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• pp.375-386
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• 2004

갈수량은 수자원의 개발 및 관리에 매우 중요한 인자중의 하나이다. 신뢰성 높은 갈수량을 측정하기 위해 한국수자원공사는 2000년도에 용담댐 시험유역에 5피트 규격의 파샬플륨을 설치하였다. 파샬플륨은 유량측정을 하기 위해 독특한 모양을 가지고 있으며, 부정확한 유량관측을 유발하는 퇴사문제를 거의 해결한 시설물이다. 본 연구에서는 3차원 CFD (Computational Fluid Dynamics) 모형으로 5가지 수위에 대해서 완전월류(free flow)시 파샬플륨의 유동을 해석하였다. CFD모형에 의해 산정된 결과와 ISO에 제시된 유량공식, USBR에 제시된 유량공식 및 수위-유량관계식으로 산정한 유량을 비교하였다. 그 결과 ISO와 USBR의 공식에 의해 산정된 유량은 거의 동일했으나, 3차원 CFD모형에 의한 유량은 경험공식에 의한 유량보다 9%정도 크게 나타났고 수위-유량관계식에 의한 유량은 경험공식에 의한 유량보다 16%정도 작게 나타났다.

• 한국환경과학회지
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• 제23권4호
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• pp.543-552
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• 2014

Fixed Electromagnetic Wave Surface Velocimetry (Fixed EWSV) has been started to be used to measure flood discharge in the mountain stream, since it has various advantages such that it works well to continuously measure stream discharge even in the night time as well as very strong weather. On the contrary, the Fixed EWSV only measures single point surface velocity, thus it does not consider varying feature of the transverse velocity profile in the given stream cross-section. In addition, a conventional value of 0.85 was generally used as the ratio for converting the measured surface velocity into the depth-averaged velocity. These aspects could bring in error for accurately measuring the stream discharge. The capacity of the EWSV for capturing rapid flow velocity was also not properly validated. This study aims at conducting error analysis of using the EWSV by: 1) measuring transverse velocity at multiple points along the cross-section to assess an error driven by the single point measurement; 2) figuring out ratio between surface velocity and the depth-averaged velocity based on the concurrent ADCP measurements; 3) validating the capacity of the EWSV for capturing rapid flow velocity. As results, the velocity measured near the center by the fixed EWSV overestimated about 15% of the cross-sectional mean velocity. The converting ratio from the surface velocity to the depth-averaged velocity was 0.8 rather than 0.85 of a conventional ratio. Finally, the EWSV revealed unstable velocity output when the flow velocity was higher than 2 m/s.

• 한국습지학회지
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• 제24권1호
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• pp.52-58
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• 2022

최근 낙동강 하구의 통합물관리를 위한 다양한 노력과 연구가 진행되고 있다. 그러한 연구 중 하나로 3차원 고정식 초음파 유속계를 이용한 수문별 개도 방류량의 측정이 수행되고 있으나, 개도별 방류량 산정식 도출을 위한 실측 성과를 활용한 수리학적 및 통계적 처리 절차와 기법에 대한 연구는 기초적인 수준에 머물고 있다. 이에 본 연구에서는 3차원 고정식 초음파 유속계 측정자료를 이용한 자료 처리 기법을 개발하여 측정 데이터 기반의 유량계수 산정하고 이를 이용하여 방류량 산정식 개발 적용성을 검토하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.349-354
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• 2001

The present study addresses the open end correction associated with the reflection and discharge phenomena of a weak shock wave from an open end of a duct. The open end correction of the weak shock wave is investigated experimentally and by numerical computation. An experiment is made using a simple shock tube with an open end, and computation is performed to simulate the experimental flow field using the unsteady, axisymmetric, compressible, flow governing equations. The results obtained show that an open end correction should be involved for shock wave discharge and reflection problems generated from the exit of the duct with an open end baffle plate. With a baffle plate less than three times the duct diameter, it is found that the open end correction is a function of both the diameter of the baffle plate and normal shock wave magnitude. However, for a baffle plate larger than three times the duct diameter, it is independent of the baffle plate diameter. The present computations predict the results of shock tube experiment with good accuracy. A new empirical equation for prediction of the open end correction is found for the weak shock reflection and discharge phenomena occurring at the open end of the duct with and without a baffle plate.

• 한국전산유체공학회지
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• 제14권1호
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• pp.70-77
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• 2009

In this study, time-dependent numerical analysis was carried out to investigate the plasma jet impingement on a flat plate, and a compressible form of two-dimensional inviscid gas dynamics equations were solved using the flux corrected transport algorithm. The mathematical modeling of Joule heating in the polycarbonate capillary bore and the mass ablation from the bore wall was incorporated in the numerical analysis and the series of computation was performed for three cases depending on the distance of the opposing plate from the capillary exit. The computational results reveal that the presence of the opposing plate does not affect the flow conditions inside the capillary when compared to the case of open-air plasma discharge. In the exterior region, the flow structure shows the typical supersonic underexpanded jet which consists of the strong Mach disk in front of the opposing plate and the barrel shock at the side of the jet. It is found that the shock evolution becomes more quasi-steady when the plate distance decreases. Also, the effects of the distance between the capillary bore exit and the opposing plate on the flow conditions along the opposing plate are investigated and the pressure variation on the plate shows more complicated interaction between the plasma discharge and the opposing plate when the location of plate becomes closer to the capillary exit.