• Journal of Advanced Marine Engineering and Technology
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• 제38권10호
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• pp.1200-1205
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• 2014

The effect of nanofluids on the heat transfer performance of a pulsating heat pipe has been experimentally investigated. Water-based diamond nanofluid and aluminium oxide ($Al_2O_3$) nanofluid were tested in the concentration range of 0.5-5%. The pulsating heat pipe was constructed using clear Pyrex tubes of 1.85 mm in inner diameter in order to visualize the pulsating action. The total number of turns was eight each for heated and cooled parts. The supply temperatures of heating water and cooling water were fixed at $80^{\circ}C$ and $25^{\circ}C$ respectively. The liquid charging ratio of the nanofluid was 50-70%. The test results showed that the case of 5% concentration of diamond nanofluid showed 18% increase in heat transfer rate compared to pure water. The case of 0.5% concentration of $Al_2O_3$ nanofluid showed 24% increase in heat transfer rate compared to pure water. But the increase of $Al_2O_3$ nanofluid concentration up to 3% did not show further enhancement in heat transfer. It is also observed that the deposited nanoparticles on the tube wall played a major role in enhanced evaporation of working fluid and this could be the reason for the enhancement of heat transfer by a nanofluid, not the enhanced thermal conductivity of the nanofluid.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.17-20
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• 2004

The purpose of this study is to arrange the digital maps of Hamamatsu City and to construct the map information system to support the prediction and restoration of Tokai earthquake disasters. The authors arrange the land condition map and compute the populations of each land surface conditions and revealed that $37\%$ of the whole population lives in the safe land, but $63\%$ lives in the rather unsafe surface condition. The authors also arrange the digital map of the main lines of water supply pipe lines in corporation with the Hamamatsu City Water Supply Department and revealed the rather dangerous pipe line area in case of Tokai earthquake.

• 상하수도학회지
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• 제35권6호
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• pp.465-476
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• 2021

Scale and rust generation in water pipes is a common phenomenon when cast iron water pipes have been used for a long time. A physical water treatment device is known among various means for suppressing rust in a water pipe, and a zinc ionization device for putting zinc metal into a pipe and emitting the zinc cation into water is one of such devices. This research measured the amount of zinc ion generated, which is known to exhibit an effect of inhibiting rust and scale generation in a pipe, and examined the scale and rust inhibition effect of the ionization device installed for ground or building water supply. In the case of distilled water, the concentration of zinc ion increased by circulating water in the ionization device several times, and it was verified to be hundreds of ㎍/L, and in the case of discharging ground or tap water, it was verified to be tens of ㎍/L. In addition, a verification pipe was installed to confirm the change inside the pipe before and after installation of the zinc ionization device, and the internal condition of the pipe was observed 3 months to several years after installation. It was confirmed that the corrosion area of the surface of the pipe was no longer increased by installing a corrosion inhibitor, and if the pipe was already filled with corrosion products, the amount of corrosion products gradually decreased every year after installation. The phenomenon of fewer corrosion products could be interpreted as expanding the space in the pipe due to the corrosion product as Fe₂O₃ adhered to the inner surface of the pipe and turned into a smaller black Fe₃O₄. In addition, we found that scale such as CaCO₃ together in the corrosion by-products gradually decreased with the attachment of the ionization device.

• 복합신소재구조학회 논문집
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• 제6권4호
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• pp.16-23
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• 2015

The industrialization and urbanization forced to increase the density of pipelines such as water supply, sewers, and gas pipelines. The materials used for the existing pipe lines are mostly composed of concretes and steels, but it is true that the development for more durable and efficient materials has been continued performed to produce long lasting pipe lines. Recently, underground pipes serve in diverse applications such as sewer lines, drain lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, etc. In this paper, we present the result of investigation pertaining to the structural behavior of unplasticized polyvinyl chloride (PVC-U) flexible pipes buried underground. In the investigation of structural behavior such as a ring deflection, pipe stiffness, 4-point bending test, experimental and analytical studies are conducted. In addition, pipe stiffness is determined by the parallel plate loading tests and the finite element analysis. The difference between test and analysis is about 8% although there are significant variations in the mechanical properties of the pipe material. In addition, it was found by the 4-point bending test there is no problem in the connection between the pipes by coupler.

• 한국방재학회 논문집
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• 제8권5호
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• pp.15-21
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• 2008

본 연구의 목적은 현재 지방자치단체에서 수행하는 상수관로 개량 및 교체 사업시 상수관로의 노후도 평가를 위한 항목별 가중치를 산정하는 것이다. 상수도시스템에 상수관로의 노후도 항목은 지역 및 위치, 토지이용 등의 특성에 영향을 받을 수 있다. 본 연구에서는 국내외 자료를 바탕으로 국내 실정에 맞는 노후도 항목 16개를 선정하였다. 또한, 노후도 항목별 세분화된 가중치 산정을 위해 실무업체를 선정하여 해당 전문가들을 대상으로 노후도 항목별 중요도에 대한 설문을 실시하였다. 설문 조사 방법으로는 델피법을 이용하여 이 결과를 바탕으로 계층적분석과정(AHP)을 적용하여 노후항목별 가중치를 산정하였다. 분석결과 국내 실무에 적합한 16개 결함항목별 점수배점표를 작성하여 명확한 판단기준을 마련하였으며 관거 개량사업에 있어서 복잡한 의사결정 문제들에 대한 활용 가능성을 제시하였다.

• 환경위생공학
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• 제15권4호
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• pp.59-77
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• 2000

This study was carried out to investigate on several factors, which contaminative the water quality through the water pipe during feeding water, in 42 largescaled apart-ments(total 84 cases) and assayed the Volatile Organic Compounds(VOCs) and concen-tration of heavy metals that inflow and outflow in reservior water in Jeonnam area(Mokpo, Suncheon, Yeosu) from January 1999 to December 1999. The results obtained were summarized as follows ; 1. The quality of the water pipe composition in the order of frequency in the quality of water pipes were Copper(45.2%)> Zinc(38.9%)> Stainless steel(9.5%)> PVC(4.8%)> PM(2.4%) in observing 42 sites. All of the drain pipes were used the cast iron quality. 2. The result of certification curve from 12 items(17kind) of VOCs was $1.0-4.0{\mu{g}}/{\ell}$ range, a coefficient of correlation was shown 0.99 over. A MDL of each substance range was within $0.1-1.0{\mu{g}}/{\ell}$. 3. The result of the assay, 5 kinds(Viny chloride, Dichloromethane, Ethylbenzene, M,P-xylene, Styrene) of the VOCs of 14 kinds was not detected and the other items were detected slightly. The detection rate of one item and over in total VOCs samples, were 25.9% in inflow and 27.9% in outflow. And frequency of detect in inflow/outflow of THM(Chloroform, Bromodichloro-methane, Dibromochloromethane, Bromoform) were shown higher than 94.1%, 97.0% each stages. It comes to the conclusion that all of the samples were reason able for drinking water standards. 4. The coefficient of correlation were reasonable, it shown 0.999 over in $0.1-1.0{\mu{g}}/{\ell}$ of a measuring range conditions of 4kinds in organic substance(Zn, Cu, Fe, Mn). 5. The results were showed suitability in 78 cases(92.9%) and unsuitability in 6 cases (7.1%), in 84 cases of in organic substances. Compare to inflow stage, mean concentrations of heavy metal, were increased slightly in Zn, Cu, Fe except Mn than outflow stage. The result of the mean concentration in organic substance inflow and outflow in the apartment water tank using Pair-compared T-test, in 95% reliance index, were $0.179mg/{\ell}(0.151-0.307mg/{\ell})$ in Zinc, $0.136mg/{\ell}(0.113-0.230mg/{\ell})$ in Copper, $0.052mg/{\ell}(0.048-0.098mg/{\ell})$ in Fe, and there was a bit growing tendency but there was no differece in Mn. 6. The mean concentration of Copper which used Cu pipe as a water supply pipe in apartment were $0.216mg/{\ell}(0.161-0.338mg/{\ell})$ in case of the Zine pipe were $0.286mg/{\ell}(0.204-0.435mg/{\ell})$. It shows that the detection rate was more higher than the other material used in Cu or Zn as the water supply pipe. We supposed to Cu and Zn substance were gushing out water supply pipe.

• 대한환경공학회지
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• 제34권7호
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• pp.473-479
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• 2012

하수재이용은 부족한 수자원 문제를 해결할 수 있는 대표적인 대안으로 주목을 받고 있다. 본 연구에서는 하수재이용수의 공급시 관망내에서 일어날 수 있는 관의 부식과 수질변화에 대한 연구를 모형관망을 이용하여 수행하였다. 관 재질은 아연도강관(GSP), 주철관(CIP), 스테인레스강관(STSP), PVC관(PVCP)을 이용하였고, 하수재이용수와 수돗물을 각각 공급하여 비교 및 평가하였다. 하수재이용수를 모형관망에 공급하는 루프테스트를 수행한 결과, 관 재질별 시편의 무게 감소량은 CIP > GSP > STSP ${\approx}$ PVCP의 순으로 나타났다. 또한, 하수재이용수는 수돗물과 비교하여 부식속도가 높게 나타났는데, CIP의 경우, 하수재이용수의 초기 부식속도가 3.511 mdd, 수돗물은 2.064 mdd를 나타내었고, 90일간의 부식속도는 하수재이용수 0.833 mdd, 수돗물 0.294 mdd를 나타내었다. 또한, GSP도 하수재이용수의 초기 부식속도가 2.703 mdd, 수돗물은 2.499 mdd를 나타내었고, 90일간의 부식속도는 하수재이용수 0.349, 수돗물 0.248 mdd로 CIP에서 나타난 경향과 유사하였으며, 시간이 지남에 따라 부식속도가 감소하는 경향을 나타내었다. 루프테스트를 수행하는 과정에서 관 재질별로 하수재이용수의 수질변화를 관찰한 결과, 암모니아성 질소의 경우, 부식이 크게 발생한 CIP 및 GSP에서 부식이 발생하지 않은 STSP 및 PVCP와 비교하여 질산염으로 전환되는 비율이 월등히 높았고, 부식생성물이 가장 많은 CIP에서 질산성 질소의 탈질이 가장 높게 일어나는 현상을 관찰할 수 있었다. 또한, CIP에서는 SRB (Sulfur Reducing Bacteria)에 의한 황산이온의 소모가 나타났으며, EDS (Energy Dispersive X-ray spectrometer System) 분석 결과 MIC (Microbiologically Induced Corrosion)가 있었음을 확인할 수 있었다.

• 한국방재학회 논문집
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• 제8권6호
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• pp.31-36
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• 2008

배수시설은 합리적인 계획으로 배치하여 시간적으로 변동하는 수요량에 대하여 적정한 수질의 물을 적정한 압력으로 연속적이면서 안정적으로 공급해야 한다. 또한 상수관 파괴 같은 사고가 발생했을 경우에도 용수 수요자에 대한 영향을 최소화 할 수 있는 안정성이 높은 시설을 목표로 구축되어야 한다. 본 연구에서는 상수관 파괴에 의한 피해를 합리적으로 경감시킬 수 있는 방법을 제시하였다. 본 연구를 위해 기존의 상수관 파괴에 의한 피해영역 산정기법과 신뢰도 산정기법을 통해서 상수관망을 분석하고 상수관 파괴에 의한 피해 경감기법을 도출하였다. 분석결과 minimum cutset에 속하는 상수관의 내구성을 중요우선순위에 따라 향상시킴으로써 상수관 파괴에 의한 피해를 효과적으로 경감시킬 수 있었으며 제안된 방법을 Cherry Hill 상수관망에 적용하여 적용성을 검증하였다.

• 한국방재학회 논문집
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• 제8권6호
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• pp.15-20
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• 2008

상수관망의 수리해석 방법은 demand-driven analysis와 pressure-driven analysis로 구분할 수 있으며, 급작스런 용수수요증가, 관거파괴 등과 같이 비정상운영상태인 용수공급시스템의 수리모의에 demand-driven analysis를 사용할 경우 비현실적인 결과를 줄 수 있다. 특히 현재 국내에서는 비상상황에 대한 비상급수계획 수립 시에 demand-driven analysis를 사용하고 있으나, pressure-driven analysis의 적용을 통한 비상급수계획의 적정성 평가가 수행되어야 할 것이다. 본 연구에서는 pressure-driven analysis를 위해 최근 개발된 WaterGEMS모형을 이용하여 2007년 수도정비 사업을 계획한 J시의 비상급수계획의 적정성을 평가하였다. 적용 결과 소블럭의 용수공급 안정성 향상을 위한 방안 제시가 가능하였으며, 수립된 비상급수계획이 적합한 것으로 판단되었다.

• Korean Journal of Hydrosciences
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• 제8권
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• pp.31-40
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• 1997

Flow carrying capacity of water distribution systems is getting reduced by deterioration of pipes in the systems. The objective of this paper is to present a managerial decision-making model for the rehabilitation of water distribution systems with a mininum cost. The decisions made by the model also satisfy the requirements for discharge and pressure at demanding nodes in the systems. Replacement cost, pipe break repair cost, and pumping cost are considered in the economic evaluation of the decision along with the break rate and the interest rate to determine the optimal replacement time for each pipe. Then, the hydraulic integrity of the water distribution system is checked for the decision by a pipe network simulator, KYPIPE, if discharge and pressure requirements are satisfied. In case the system does not satisfy the hydraulic requirements, the decision made for the optimal replacement time is revised until the requirments are satisfied. The model is well applied to an existing water distribution system, the Seoul Metropolitan Water Supply System (1st Phase). The results show that the decisions for the replacement time determined by the economic analysis are accepted as optimal and hydraulic integrity of the system is in good condition.