• 한국물환경학회지
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• 제28권2호
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• pp.285-291
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• 2012

Generally, the rainfall and the influent of wastewater treatment plants (WWTPs) have strong relationship at the case of combined sewers. With the fact that the influent variations in terms of quantity and sewage quality is the most common and significant disturbance, the impact factor to the characteristics of sewage should be searched for. In this paper, the relationship between weather conditions such as humidity, temperature and rainfall and influent flowrate and contaminant concentration was analysed using factor analysis. Additionally, 3 influent types were deduced using cluster analysis and the distributions of operational variables were compared to the each groups by one-way ANOVA. The applied dataset were clustered to three groups that have the similar weather and influent conditions. These different conditions can cause the different operating conditions at WWTPs. That is, the Group 1 is for the condition with high humidity and rainfall, so DO concentration in the reactor was very high but MLSS concentration was very low because of too large flowrate. However, the Group 3 is classified to the case having low humidity, temperature, and rainfall, therefore, the SRT was the longest and the SVI was the highest due to the worst settleability in the winter for a year.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.78-81
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• 2009

연료펌프에 대한 수력성능시험을 상온의 물을 매질로 하여 실시하였다. 시험된 연료펌프는 개방형 가스발생기 방식의 75톤급 액체로켓엔진에 적용할 목적으로 개발 중에 있다. 시험 결과, 연료펌프는 설계요구조건을 만족하였으며, 설계 유량에서의 양정과 효율은 수치해석에서 추정된 값보다 높았다. 또한 후방 베어링의 출구 압력이 예상보다 높았는데 이는 바이패스 배관의 입구가 좁기 때문이었다. 그리고 바이패스 곡관부의 차압 측정으로 누설 유량을 유추할 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.41-45
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• 2009

본 연구에서는 고농도 과산화수소와 케로신을 각각 산화제와 연료로 사용하는 소형 이원추진제 추력기의 설계/제작 및 인젝터 성능특성 파악을 위한 수류시험을 수행하였다. 본 개발모델에서는 점화기, 인젝터, 막냉각 시스템을 통합하여 운용이 가능한 구조의 믹싱헤드를 적용하였으며, 각 부분으로의 공급유량 변경이 가능하도록 하여 최적 설계의 실험적 검증 및 효율성을 극대화하고자 하였다. 마지막으로 수류시험을 통해 인젝터 유량 및 추진제 분사패턴을 확인하였으며, 믹싱헤드의 설계 타당성을 검증하였다.

• 한국환경과학회지
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• 제18권9호
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• pp.983-992
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• 2009

The purpose of the present study is to analyze pollutant runoff characteristics from non-point sources in Joman River basin. The present study contains analyzed results of rainfall and SS, BOD, COD, TN, TP runoff from Joman River basin. This study contains a sensitivity analysis of parameters that affect the simulation results of rainfall and pollutants runoff. Result of the sensitivity analysis shows that proportion of watershed and impervious areas is the most sensitive to peak discharge and total flowrate for rainfall runoff and that WASHPO is the most sensitive parameter for pollutants runoff. For parameter estimation and verification, flowrate and water quality is measured at the Kangdong Bridge in Haeban stream. A single rainfall event is use to perform parameter estimation and verification. Results of the present study show that total pollutant loads of Joman River basin is 11,600 ton of SS, 452 ton of BOD, 1,084 ton of COD, 515 ton of TN, and 49 ton of TP, respectively. In addition, it is found that contribution ratio of non point source and total source is 89% of SS, 63% of BOD, 61% of COD, 21% of TN, and 32% of TP, respectively.

• 한국수소및신에너지학회논문집
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• 제14권1호
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• pp.61-68
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• 2003

This paper presents the methodology to analyze flow duration characteristics and performance prediction technique for small hydro power(SHP) Plants and its application. The flow duration curve can be decided by using monthly rainfall data at the most of the SHP sites with no useful hydrological data. It was proved that the monthly rainfall data can be characterized by using the cumulative density function of Weibull distribution and Thiessen method were adopted to decide flow duration curve at SHP plants. And, the performance prediction technique has been studied and development. One SHP plant was selected and performance characteristics was analyzed by using the developed technique, Primary design specfications such as design flowrate, plant capacity, operational rate and annual electricity production for the SHP plant were estimated, It was found that the methodology developed in this study can be a useful tool to predict the performance of SHP plants and candidate sites in Korea.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.174-179
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• 2000

Ultrafine particles have been used widely in many high technology industrial areas. The spherical nonagglomerated and uniform nanometer-size $SiO_2$ particles are synthesized by the direct injection of TEOS(Tetraethyorthosilicate) using electro-hydrodynamic spray ins method. Electro-hydrodynamic spray can generate in the range of submicron-size TEOS particles with high electric charge by applying a high electric field between the liquid injection nozzle and the reaction tube. This TEOS particles are thermally decomposed or oxidized to produce nanometresized $SiO_2$ particles in the reaction tube. Spherical, nonagglomerated and ultrafine particle generated and examined at furnaced temperature, $800^{\circ}C$ and TEOS flowrate of 0.49 or $1.00cm^3/hr$ using SEM and SMPS. As the total gas flowrate changes from 1.51pm to 5.01pm, the mean diameter of $SiO_2$ particle decreases from 120 nm to 68nm.

• 대한기계학회논문집B
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• 제25권1호
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• pp.78-86
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• 2001

The Gasoline Direct Injection(GDI) system has been highlighted due to the improvement of fuel consumption and the control of exhaust emission from gasoline engines. The GDI system includes a high injection pressure, smaller mean diameter, good spray characteristics and stability. We were interested in the development for gasoline direct swirl injector(GDSI) in which the swirler is specially designed with an incident angle. Nymerical analysis was utilized to investigate the internal flow of GDSI with a goal to determine the swirl incident angle and needle lift. Accordingly, it describes characteristics of a GDSI in which the flowrate and spray characteristics are satisfied. especially the spray tip penetration decreases, compared with other type GDI, mean diameter of droplets is from 20${\mu}{\textrm}{m}$ to 25${\mu}{\textrm}{m}$ and spray angle ranges from 64$^{\circ}$to 66$^{\circ}$.

• 설비공학논문집
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• 제6권4호
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• pp.354-364
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• 1994

Experiments have carried out to investigate the effects of parameters, such as mass ratio of R141b-to-water, stirrer speed, brine inlet temperature, brine flowrate, and additives, on the performance of the cool storage system using R141b clathrate. The cool storage system in this experiment was composed of storage tank, refrigerator, and heater. The results show that the mass ratio of R141b-to-water, 1 : 3~1 : 3.5 gives the best performance and the stirring speed has optimum point as 600rpm. At this speed impeller Reynolds number is $1.01{\times}10^5$. The lower the inlet brine temperature and the highter the brine flowrate, the better performance. The addition of metal powder turned out to reduce the degree of supercooling. The supercooling reduction was proportional to the amount of the metal power. However when metal powder was added more than 0.1 wt%, there was no additional supercooling reduction. The surfactants shortened the time consumed for cool storage to the half of no surfactant added case.

• 설비공학논문집
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• 제6권3호
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• pp.175-181
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• 1994

This paper deals with the correlation of absorption rate in absorber and evaporation rate in evaporator. The evaporator consists of a copper tube of 10mm dia, and 600mm long and chilled water flowing through the tube is fed by the chilled water circulator. The flowrate of LiBr-water solution in the absorber plays a significant role in determining the magnitude of the heat transfer rate from chilled water to refrigerant There exists a flowrate of solution which has a maximum value of heat transfer. It is interesting to note that the absorption rate of absorber increases with increasing the heat transfer rate of the evaporator. Also, absorption rate increases with evaportation rate, and the ratio(the former/the other) depends on the inlet temperature of LiBr-water solution in the absorber. The heating capacity in the absorber is higher than the refrigerating capacity in the evaporator.

• 환경영향평가
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• 제15권2호
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• pp.157-163
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• 2006

The purpose of this study is to understand imperviousness impact for the characteristics of stormwater runoff and water temperature. The land-use map was used to estimate the watershed imperviousness(percent of impermeable area) and the RMS(Remote Monitoring System) was used to evaluate the stormwater runoff of watershed. This study was investigated for two streams(Jiam and Gongji) in Chunchon City. The detailed results of these studies are as follows; The imperviousness(%) of two watersheds(Jiam and Gongji) estimated by spatial analysis which is main function of GIS were 0.24% and 24.16%. So, Gongji watershed as urban area was about 100 times than jiam watershed as forest area. In case of rainfall of low intensity, stormwater runoff flowrate in higher imperviousness area(Gongji) was more than it in forest area(jiam). Also, The time to peak flowrate(Tp) was short in Gongji stream and the water temperature difference between Gongji and Jiam stream was about $4.4^{\circ}C$ in summer.