• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 한국에너지공학회 1995년도 춘계학술발표회 초록집
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• pp.207-212
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• 1995

본 연구에서는 발전소 응축기를 시뮬레이션 할 수 있는 프로그램을 개발하였다. 관 내외 측 열전달계수의 계산에는 기존 상관식들과 응축 모델을 사용하였고 $\varepsilon$-NTU 방법을 사용하여 응축기를 해석하였다. 실제 응축기를 모사하기 위하여 관다발 보정계수 및 화울링 계수도 도입하였다. 이 프로그램을 사용하여 기존 평관을 대체할 전열촉진관의 형상을 도출하였다. 시뮬레이션 결과 전열촉진관을 사용하면 증기 응축 온도를 6 - 8 $^{\circ}C$ 정도 낮출 수 있음을 알 수 있었다.

• Proceedings of the Korean Nuclear Society Conference
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• 한국원자력학회 1995년도 추계학술발표회논문집(2)
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• pp.824-828
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• 1995

월성원전에서 삼중수소에 의한 작업자 피폭 및 환경방출량을 가능한 한 낮게 유지하기 위해서는 계통중수중에 축적되는 삼중수소를 근원적으로 제거할 수 있는 삼중수소제거시설이 필수적이다. 삼중수소제거공정은 방사선 안전성과 에너지 효율 측면에서 액상촉매교환과 초저온증류공정의 복합공정이 가장 효과적인 것으로 알려지고 있다. 본 연구에서는 월성원전의 후속기를 고려하여 용량이 연간 8MCi의 삼중수소제거시설에 대한 최적설계를 수행하였다. 액상촉매교환공정에 대해서는 NTU-HTU법 그리고 초전온증류공정에는 Fenske-Underwood-Gilliland법을 이용하여 공정을 해석하였고 공정내 삼중소소의 재고량이 최소가 되는 최적의 설계변수들을 제시하였다.

• Communications of the Korean Mathematical Society
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• 제26권2호
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• pp.215-227
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• 2011

In this paper we introduce a class $h^{-\infty}_{\Phi}(\mathbb{B})$ of weighted spaces of harmonic functions in the unit ball $\mathbb{B}$ of $\mathbb{R}^n$. We dene weakly sufficient sets in this space and give an explicit construction of countable sets of such a type. Various examples of weight functions are also discussed.

• Journal of Korean Society of Environmental Engineers
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• 제34권10호
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• pp.651-655
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• 2012

This study aimed to investigate the effect of an inorganic conditioner composed of natural inorganic materials on the dewaterbility of sewage sludge and compare the performance with those of conventional organic polymeric conditioners. A dosage of 2.0 mg inorganic conditioner/g sludge TS decreased time to filter test (TTF), specific resistance to filtration (SRF), water content of dewatered sludge cake, turbidity from 146 to 41 sec, from $8.3{\times}10^{14}$ to $2.4{\times}10^{14}$ m/kg, from 82.1 to 77.1%, from 112 to 61.1 NTU, respectively, which was compatible to the conventional cation organic polymer. An inorganic conditioner would be used in sewage sludge treatment as a suitable alternative conditioner. Regression analysis showed a strong relationship among TTF, SRF, and water content.

• Membrane Journal
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• 제23권6호
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• pp.460-468
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• 2013

This study reviewed optimum dosage rate of coagulant and ability to remove dissolved organic carbon without sedimentation in conventional water purification plant. It was confirmed that floc formated by pre-treatment process was broken by impeller of booster pump. Optimum dosage rate of coagulant was 4 mg/L (as PACl 17%) for floc formation through blend, coagulation and after passing through the pump when turbidity of raw water was less than 10 NTU. And average removal rate of dissolved organic carbon was 43% at that time. Maximum removal rate of dissolved organic carbon was 48%, even though coagulation rate was increased gradually until 8 mg/L (as PACl 17%). So removal rate of dissolved organic carbon is not much improved even if dosage rage of coagulant increase. TMP of PVDF (polyvinylidene flouride) pressurized MF process without pre-treatment operated at 0.54 bar and TMP of PVDF pressurized MF process with pre-treatment operated at 0.41 bar.

• Journal of Korean Society of Water and Wastewater
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• 제20권1호
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• pp.71-78
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• 2006

The removal of protozoa in the coagulation process was evaluated under the different pH and turbidity using the jar test after the addition of polyaluminium chloride (PAC) as a coagulant. Two well-known protozoa of Cryptosporidium parvum and Giardia lamblia were tested at the same time with turbidity, the critical water quality parameter of the water treatment process. Both protozoa were removed about 1log (and up to 2log) at the optimum injection of PAC. The source water turbidity and pH affected the removal of protozoa and turbidity. At neutral and alkaline pH, 1.3-1.7log removal of protozoa for low turbid water with 5NTU, and 1.6-2.3log removal for high turbid water with 30NTU were achieved. However, at acidic pH, maximum 0.8-1.0log and 1.1-1.2log were removed for low and high turbid water, respectively, at the optimum PAC injection of 15mg/L. The relation of protozoa and turbidity removals were expressed as the 1st order equation (significantly positive relation) in the most of the tested conditions. In addition, the relation of protozoan removals with residual turbidity were also expressed the 1st order equation (significantly negative relation), although the significance of the equations were reduced at acidic pH. Therefore, residual turbidity could be a good index of efficient protozoan removal in the coagulation process, probably except at the low pH condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제33권6호
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• pp.403-410
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• 2009

This paper proposes a new approach to find the optimum ratios between sizes of the heat exchangers of the heat recovery steam generator (HRSG) system with limited size to maximize the efficiency of the steam turbine (bottom) cycle of combined cycle power plants (CCPP), but without performing the bottom cycle analysis. This could be achieved by minimizing the unavailable exergy (the sum of the destroyed and the lost exergies) resulted from the heat transfer process of the HRSG system. The present approach is relatively simple and straightforward because the process of the trial-and-error method, typical in performing the bottom cycle analysis for the system optimization, could be avoided. To demonstrate the usefulness of the present method, a single-stage HRSG system was chosen and the optimum evaporation temperature was obtained corresponding to the condition of the maximum useful work. The results show that the optimum evaporation temperature based on the present exergy analysis appears similar to that based on the bottom cycle analysis. Also shown is the dependency of size (NTU) ratios between the heat exchangers on the inlet gas temperature, which is another important factor in determining the optimum condition once overall size of the heat recovery steam generator is given. The present approach turned out to be a useful tool for optimization of the singlestage HRSG systems and can easily be extended to multi-stage systems.

• Journal of Environmental Impact Assessment
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• 제15권4호
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• pp.259-270
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• 2006

The purpose of this study is to understand the relation between the land use status in watersheds and stream turbidity. Major water quality components (flow rate, turbidity, SS, BOD, TN, TP, etc.) of two streams (Jaun and Naerin) and the land use status for each correspondent watershed have been analyzed through the field sampling and the geographical overlaying of land use and watershed map. The detailed results of this study showed that; turbidity has been increased rapidly from 1.9 to 13.0 NTU for Jaun Stream, 0.4 to 0.7 NTU for Naerin Stream, due to the increased flow rate during the period of June. The agricultural area of the Jaun watershed was $13.5km^2$ (10.1% of the overall watershed), comparing to $2.0km^2$(1.4%) of upper watershed of Naerin stream. The forest was widely distributed along the 30m buffering zone from the center of Naerin stream, which comprised 64.14% of the whole watershed area. But in case of the Jaun, the ratio of forest was 17.84%, while the ratio of farming field was 30.33%.

• Journal of Korean Society of Environmental Engineers
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• 제36권4호
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• pp.251-257
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• 2014

This research is focused on coagulation and sand filtration process as a pretreatment of RO seawater desalination. RO systems require sufficient and reliable pretreatment process to produce superior quality of RO feedwater that can mitigate RO membrane fouling. This experiment was conducted to investigate the effectiveness of coagulation and filtration process under various experimental conditions including different coagulant dose, flocculation mixing intensity and time, turbidity, and filtration rate. The experimental results showed that the optimum pretreatment conditions resulting in lower SDI value suitable for RO feedwater were coagulation pH 6.5, raw water turbidity greater than 4 NTU, and media bed depth greater than 550 mm. However, flocculation mixing intensity, coagulant dose, and filtration rate relatively affected little on the filtration efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제17권11호
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• pp.732-739
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• 2016

In Korea, the summer is hot and humid, and much electricity is consumed for air conditioning. Thus, the simultaneous usage of an indirect evaporative cooler and a common air conditioner could reduce the sensible heat and save electricity. This study developed a U-type cross-counter flow indirect evaporative cooler (IEC) made of plastic and paper. The efficiencies were compared with those of a cross-flow IEC. The specimen was $500mm{\times}500mm{\times}1000mm$. the results show that the indirect evaporation efficiencies of the cross-counter flow sample were 6-21% higher than those of the cross-flow sample. The pressure drops of the cross-counter sample were 51-66% higher. Thermal analysis based on the -NTU method predicted the experimental data within 10%. The electrical energy saved by the use of the cross-counter flow IEC was larger than that of the counter flow IEC, and the difference increases with the velocity. However, the the cross-counter IEC is two times larger than the cross-flow IEC, which may increase the material cost and water usage.