• 멤브레인
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• 제9권4호
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• pp.193-201
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• 1999

기존의 정수처리 공정인 응집 침전 과정을 대체하여 분리막을 이용한 상수처리 시스템의 개발을 목적으로한다. 따라서 4가지 형태의 정수처리 공정과 분리막의 분획 분자량을 변화시켰을 때 막 투과수의 변화와 안정적이며 높은 투과수를 얻기 위해 필요한 운전 조건의 최적화를 실험하였다 실험결과 한외여과막이 정밀여과막보다 막 투과수 감소경향이 완만했으며 초기 투과수 회복율은 더 높았다. 수질 분석의 결과 한회여과막이 정밀 여과막보다 우수하였지만 전처리에 의한 차이는 나지 않았다. 운전 조건에 따른 flux 는 온도, 선속도가 높을수록 압력이 낮을수록 flux 감소율이 적은 경향을 나타내었다.

• Korean Membrane Journal
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• 제7권1호
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• pp.19-27
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• 2005

PP hollow fiber membrane was hydrophilized by EVOH dip coating followed by low temperature plasma treatment and UV irradiation. EVOH coating attained high water flux without any prewetting but its stability did not guaranteed at high water permeation rate. At high water permeation rate, water flux declined gradually due to swelling and delamination of the EVOH coating layer causing pore blocking effect. However, plasma treatment reduces the swelling, which suppress delamination of the EVOH coating layer from PP support result in relieving the flux decline. Also, UV irradiation helped the crosslinking of the EVOH coating layer to enhance the performance at low water permeation rate. FT-IR and ESCA analyses reveal that EVOH dip coating performed homogeneously through not only membrane surface but also matrix. Thermogram of EVOH film modified plasma treatment and W irradiation show that crosslinking density of EVOH layer increased. Chemical modification by plasma treatment and UV irradiation stabilized the hydrophilic coating layer to increase the critical flux of the submerged membrane.

• 한국응용과학기술학회지
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• 제41권1호
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• pp.19-26
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• 2024

Recently, separation membranes have been applied to fields such as water supply, sewage treatment, gray water reuse, and air pollution control. Chemical cleaning technology is attracting attention among the methods of reusing these expensive separation membranes. It was found that the separation membrane could be regenerated using chemical cleaning. Specifically, it was found that the use time of the separation membranes regenerated by chemical cleaning was sustainable for more than 1,700 hours. Additionally, it was found that the flux recovery ratio after chemical cleaning was maintained at least 60%. In addition, the flux recovery ratio of HYDREX 4710, an organic membrane cleaner, and 4703, an inorganic membrane cleaner, was 76% and 62%, respectively, showing the highest flux recovery ratio among the chemicals used. Considering that the target raw water of this study is biological secondary treatment water, it was suggested that chemical cleaning could be actively used to regenerate separation membranes in future water treatment.

• 한국수자원학회논문집
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• 제52권1호
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• pp.11-19
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• 2019

본 연구에서는 인공위성 및 재분석 자료인 Global Land Data Assimilation System (GLDAS), Global Land Evaporation Amsterdam Model (GLEAM), MOD16의 실제증발산량 산출물을 활용하여 한국수자원조사기술원(Korea Institute of Hydrological Survey, KIHS)에서 관리하고 있는 청미천(cheongmicheon farmland site, CFK)과 설마천(seolmacheon site, SMK) flux tower에서 검증하였고, Triple collocation (TC) 방법을 활용하여 자료간의 불확실성 및 상관성분석을 수행하였다. 플럭스타워와의 검증 결과에서는 전반적으로 GLEAM>GLDAS>MOD16순으로 좋은 결과를 나타내었으며, 세가지 산출물의 조합(S1: flux tower vs. GLDAS vs. MOD16, S2: flux tower vs. GLDAS vs. GLEAM, S3: flux tower vs. GLEAM vs. MOD16)을 통한 TC 결과에서는 청미천(설마천)에서 GLEAM>GLDAS>MOD16>flux tower (GLDAS>GLEAM>MOD16>flux tower)순으로 좋은 결과를 나타내었다. TC 분석 결과에서 Flux tower의 error variance와 correlation coefficient가 상대적으로 좋은 결과를 나타내지 못하였으므로, 한반도 지역에서 인공위성과 재분석 자료(GLDAS vs. GLEAM vs. MOD16)만을 활용하여 TC를 적용하였다. 그 결과, GLDAS와 GLEAM이 한반도 영역에서 낮은 error variance 와 높은 correlation coefficient를 나타낸 반면, MOD16의 경우, 농지에서 낮은 correlation coefficient과 높은 error variance를 나타내었다.

• Ocean and Polar Research
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• 제26권4호
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• pp.635-646
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• 2004

Chronic outbreaks of green tide in the Nakdong estuary toll a heavy socioeconomic cost. The paper investigates the influence of sediments on the nitrogen eutrophication, being claimed as the primary cause of green tide. To measure the flux of nitrate at the sediments-water interface, sediment cores were taken in Jan., Mar., May and Sep., 2000 at Noksan located in the West-Nakdong river estuary. The dissolved oxygen was profiled and then the pore water was extracted in situ. Core samples were analyzed for their textural characteristics. Cores were incubated by a novel technique to measure the fluxes of nitrate $(NO_3^-)$ and ammonia $(NH_4^+)$ at the sediment-water interface. The dissolved oxygen was depleted usually within several millimeters in the top sediments. Nitrate started to decrease drastically at the layer where dissolved oxygen was nearly depleted. Nitrate was also exhausted within several centimeters, followed by ammonia build up rapidly. The flux at the sediments-water interface calculated from the pore water concentrations revealed that nitrate was removed from the water column into the sediments. The sediment incubation experiment confirmed the above result. On the other hand ammonia were released from the sediment to the water column. As the incubation went on, however, the nitrate concentration in the overlying water was dropped below that of a top sediment. Then the flux is reversed, i.e., nitrate was released from the sediments to the water column. The implication is that the sediment can supply nitrate to the water column if it falls below a certain level. Thus it is likely that sediments in the eutrophicated river buffers the nitrate concentration in the water column, which leads to a prolonged green tide.

• 설비공학논문집
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• 제18권1호
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• pp.55-65
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• 2006

The air and water flow distribution are experimentally studied for a round header - flat tube geometry simulating a parallel flow heat exchanger. The number of branch flat tube is thirty. The effects of tube outlet direction, tube protrusion depth as well as mass flux, and quality are investigated. The flow at the header inlet is identified as annular. For the downward flow configuration, the water flow distribution is significantly affected by the tube protrusion depth. For flush-mounted configuration, most of the water flows through frontal part of the header. As the protrusion depth increases, more water is forced to the rear part of the header. The effect of mass flux or quality is qualitatively the same as that of the protrusion depth. Increase of the mass flux or quality forces the water to rear part of the header. For the upward flow configuration, however, most of the water flows through rear part of the header. The protrusion depth, mass flux, or quality does not significantly alter the flow pattern. Possible explanations are provided based on the flow visualization results. Negligible difference on the water flow distribution was observed between the parallel and the reverse flow configuration.

• 한국습지학회지
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• 제16권3호
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• pp.347-353
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• 2014

여과분리형 생물반응조 운전에서 발생하는 flux 감소 원인을 분석하였고, 상등수 수질과 침강성 변화가 flux에 미치는 영향을 평가하였다. 또한 여과막 모듈과 역세정 장치 일체형 시스템의 특성을 평가하였다. 반응조는 17L 유효 용적의 아크릴 반응조에 $100{\mu}m$ 공경의 여과막 모듈을 통해 배출되는 여과시스템으로, 여과시간이 경과함에 따라 상등수의 수질 특히 탁도와 TOC의 수질이 악화됨에 따라 flux가 점진적으로 감소하였다. MLSS 농도가 18000mg/L 이상에서는 여과저항이 급격히 증가하였다. 상등수의 수질과 flux와의 관계를 규명하기 위해서는 MLSS 농도가 10000mg/L 이상에서는 곤란함에 따라 5000mg/L이 적절한 것으로 판단된다. 활성슬러지 플록을 파괴시켜 SVI를 250으로 조정하여 여과를 시작한 경우, 상등수의 탁도가 증가하여, 침강성이 악화됨에 따라 flux도 점차 감소하였다. 여과막 모듈과 폭기세정 장치를 일체화한 시스템에서 공기 공급은 30~60초 정도로 설정함이 적정한 것으로 나타났다.

• 한국해양공학회지
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• 제22권1호
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• pp.13-21
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• 2008

In this study a method to predict CHF(Critical heat flux) in vertical round tubes with axially non-uniform cosine heat flux distribution for water was examined. For this purpose a local condition hypothesis based CHF prediction correlation for uniform heat flux in vertical round tubes for water was developed from 9,366 CHF data points. The local correlation consisted of 4 local condition variables: the system pressure(P), tube diameter(D), mass flux of water(G), and 'true mass quality' of vapor($X_t$). The CHF data points used were collected from 13 different published sources having the following operation ranges: 1.01 ${\leq}$ P (pressure) ${\leq}$ 206.79 bar, 9.92${\leq}$ G (mass flux) ${\leq}$ 18,619.39 $kg/m^2s$, 0.00102 ${\leq}$ D(diameter) ${\leq}$ 0.04468 m, 0.0254${\leq}$ L (length) ${\leq}$ 4.966 m, 0.11 ${\leq}$ qc (CHF) ${\leq}$ 21.41 $MVW/m^2$, and -0.87 ${\leq}X_c$ (exit qualities) ${\leq}$ 1.58. The result of this work showed that a uniform CHF correlation can be easily extended to predict CHF in axially non-uniform heat flux heater. In addition, the location of the CHF in axially non-uniform tube can also be determined. The local uniform correlation predicted CHF in tubes with axially cosine heat flux profile within the root mean square error of 12.42% and average error of 1.06% for 297 CHF data points collected from 5 different published sources.

• 상하수도학회지
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• 제10권3호
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• pp.92-99
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• 1996

The effects of membrane fouling on the water permeability were examined using the hollow fiber microfiltration (HMF)membrane. A membrane module with a pore size of 0.1 micron was submerged in the permeation tank and water bath. The applied pressure was 12.4 kPa for direct solid-liquid separation of activated sludge. As the concentration of MLSS(880~2180mg/l) of the feed solution increased, the decreasing rates of the water flux increased and the membrane was clogged more rapidly. The water flux through the membrane did not increase effectively even with the increase in the applied pressure(40.0~93.3kPa). When the membrane was cleaned with water, the recovery rate of water flux were larger for lower applied pressure. The results indicated that the process of direct solid-liquid separation using HMF membrane was effective at lower pressure.

• 환경위생공학
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• 제10권1호
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• pp.12-24
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• 1995

I tried to evaluate the reason of the monthly variation of water quality according to the hydrologic character of Pal- dang reservoir inflow variation. The result of this study is as below; 1 ) COD, BOD, Total- nitrogen and Total- phosphate concentration increase generally according to the flux and Total- phosphate concentration is the most affected item by flux. 2) COD, BOD, Total- nitrogen and Total- phosphate concentration increase according the flux, but they begin to decrease at the below point ; COD · 1,154 CMS, BOD : 1,007 (CMS cubicmeter per second ) and Inflow- Concentration interrelation formula is as below; table omitted.