• 한국초전도ㆍ저온공학회논문지
• /
• 제21권2호
• /
• pp.15-21
• /
• 2019

In the mine exploration sites, sustainable treatment system of mine water with energy saving and minimized chemical additives is required. Since most of the mine water contains highly-concentrated ferrous ion, it is necessary to study on the removal method of iron ions. We propose the system consisting of two processes; precipitation process by air oxidation using solid catalyst-modified magnetite and separation process combining gravitational sedimentation and magnetic separation using a permanent magnet. Firstly, in the precipitation process (a former process of the system), we succeeded to prepare solid catalyst-modified magnetite. Air oxidation using solid catalyst-modified magnetite using $Fe_2(SO_4)_3$ as a starting material showed high iron removal capability. Secondly, in the separation process (latter process of the system), solid catalyst-modified magnetite using $Fe_2(SO_4)_3$ as a starting material can be separated by a superconducting bulk magnet and a permanent magnet.

• 설비공학논문집
• /
• 제20권1호
• /
• pp.65-74
• /
• 2008

In Korea, air source heat pump system is less efficient than conventional heat source facilities, such as ground source, river water, because the air temperature in winter season is so low that COP of air source heat pump system drops below 3.0. Therefore, the study on the application of heat pump heating and cooling systems is crucial for the efficient popularization of heat pump. In this work, we present the dynamic analysis of energy consumption for the large resident building by heat resistance-capacitance method. The system simulation of water storage air source heat pump is additionally performed by changing of sizes and locations of the hospital building. The computed results show that energy cost of water storage air source heat pump is low, so it is more economical than absorption chiller & heater.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
• /
• pp.1313-1318
• /
• 2000

Crack behaviors at the downstream face of the concrete gravity dam were studied considering influence of the wintertime air temperature. It is assumed that inside area of 15m away from the dam surface in which temperature is presumed to be $15^{\circ}C$ is not affected from the annual air temperature variation. Water temperature at the upstream face and air temperature at the other faces were considered as outer boundary conditions to get temperature distribution inside of the dam using ADINA-T. These temperature distributions were transferred to FRANC2D to obtain equivalent stress intensity factors and crack propagation paths. Results obtained from changing initial crack locations and direction, air temperatures, and water levels were discussed. And crack behaviors at the upstream face were studied partly.

• 대기
• /
• 제29권5호
• /
• pp.609-614
• /
• 2019

Cloud seeding experiment has been proposed as a way to alleviate severe air pollution problem because, if successful, artificially produced precipitation through cloud seeding could scavenge out some portion of air pollutants. As a first step to verify the practicality of such experiment, seedability of the clouds observed in Seoul is assessed by examining statistical characteristics of some relevant meteorological variables. Analyses of 9 years of Korea Meteorological Agency Seoul station data indicate that as PM₁₀ mass concentration increases, cloud amount, liquid water path, and ice water path decrease, but the difference between temperature and dew point temperature tends to increase. Such finding suggests that cloud seeding becomes less feasible as air pollution becomes more severe in the Seoul metropolitan area, at least in a statistical sense. For some individual severe air pollution events, however, seedable clouds may exist and indeed cloud seeding experiments can be successful. Therefore, detailed investigation on cloud seedability for individual severe air pollution events are highly required to make a concrete assessment of cloud seeding as a way to alleviate severe air pollution problem.

• 한국산학기술학회논문지
• /
• 제20권2호
• /
• pp.732-740
• /
• 2019

가습 소자를 이용한 증발식 가습은 건물이나 데이터 센터의 공조에 널리 사용되고 있다. 가습 소자의 성능은 가습 효율로 나타내는데 이 효율은 공기의 온습도나 물 온도에 무관하게 사용되고 있다. 본 연구에서는 데이터 센터와 건물 공조의 두 공기 조건에 대하여 셀룰로오스/PET, Glasdek의 두 소자를 사용하여 전벙 풍속과 물 온도를 변화시키며 일련의 실험을 수행하였다. 실험 결과 측정된 가습 효율은 공기 조건과 물 온도에 따라 다르게 나타났다. 심지어 건물 조건에서는 소자의 입구부에서 감습이 나타나기도 하였는데 그 이유는 공급수 온도가 입구 공기의 노점온도보다 낮았기 때문이었다. 건물 조건에서는 공급수 온도와 공기의 노점 온도 차이가 증가할수록 가습 효율은 감소하였다. 이로부터 가습 효율 모델을 적절히 세우려면 길이 방향으로 수분 전달량이 변화하는 입구 영역에 대한 해석이 중요하다고 판단된다. 셀룰로오스/PET 소자에 대하여 성능 해석을 수행한 결과 Sherwood 수는 적절히 예측하였으나 마찰 손실은 과대 예측하였다. 이는 해석시 채널 형상을 단순한 삼각형으로 가정하고 소자 표면에 형성된 액막의 영향을 무시한 때문으로 판단된다.

• 한국세라믹학회지
• /
• 제27권7호
• /
• pp.833-840
• /
• 1990

For the development of multi-functional materials which has water reducing power, air entraining power and waterproofing power as well as blending additive in cement mortar the coal ash was modified with asphalt-stearic acid or asphalt-boiled oil mixtures by mechanical treatment. And the physical properties of cement mortar blended with modified coal ashes were compared with those of the water-tightness-cement mortar and the ordinary-portland-cement mortar added with AE.water reducing agent. The mortar of coalash-blend-cement modified with asphalt-stearic mixture was increased acid about 20% in initial strengths and decreased about 20% in water absorption ratio than those of ordinary coalash-blend-cement. The mortar of coalash-blend-cement modified with asphalt-bolied oil mixture was similar to the cement mortar added with AE.water reducing agent in water reduction ratio, air entraining conents and the initial strengths, also was similar to the water-tightness-cement mortar in water absorption and water permeability ratios.

• 설비공학논문집
• /
• 제11권4호
• /
• pp.511-517
• /
• 1999

Determining the simultaneous flow rate in any particular section of piping is the important step in order to determine the size of water supply piping. Now we are using the diversity curve of common water closet in order to determine the simultaneous flow rate of water supply piping, but there is a difference between a determined flow rate of general water closet and that of water closet for water saving. This study aims to find out the fixture unit of a flush valve type water closet for water saving in office building, and to determine the correlation between the fixture units and peak flow rates on the basis of the probability theory. A flush valve type water closet for water saving that have a 7.5 second duration of flush operation with an average design flow rate 72 $\ell$/fin was considered. Simulation results indicate that the number 5 is shown to be reasonable to the fixture unit of water closet for water saving. And the design can be undersized considerably with the revised diversity curves using modified fixture unit.

• 설비공학논문집
• /
• 제16권4호
• /
• pp.349-354
• /
• 2004

Scale is formed when hard water is heated or cooled in heat transfer equipments such as heat exchangers, condensers, evaporators, cooling towers, boilers, and pipe walls. When the scale deposits in a heat exchanger surface, it is conventionally called fouling. The objective of the present study is to analyze the process of the fouling formation in a heat exchanger according to different types of water using visualization techniques. In order to experimentally investigate the formation of the fouling, this study built a lab-scaled heat exchanging system. Using the visualization techniques of Scanning Electron Microscopy (SEM) and X-Ray diffraction method, the three dimensional configurations of the fouling formation could be successfully obtained. Based on the experimental results, it was found that the configurations of the fouling formation were different when using tap water compared to river water.

• 설비공학논문집
• /
• 제20권9호
• /
• pp.614-623
• /
• 2008

This paper presents the results of a laboratory study on the thermal conductivity of and(silica, quartzite, limestone, sandstone, granite and two masonry sands)-water mixtures used for ground heat exchanger backfilling materials. Nearly 260 tests were performed in a thermal conductivity measuring system to characterize the relationships between the thermal conductivity of mixtures and the water content. The experimental results show hat the thermal conductivity of mixtures increases with increasing dry density and with increasing water content. The most widely used empirical prediction models for thermal conductivity of soils were found inappropriate to estimate the thermal conductivity of unsaturated sand-water mixtures. An improved model using an exponential relationship to compute the thermal conductivity of dry sands and empirical relationship to assess the normalized thermal conductivity of unsaturated sand-water mixtures is presented.

• 물과 미래
• /
• 제26권1호
• /
• pp.71-79
• /
• 1993

공기주입 부유구조물에 대한 압력변화의 비선형 특성과 파랑변형을 이론적 및 실험적으로 검토한다. 섭동법과 Green 공식에 의한 두가지 이론적 방법(방법I, II)이 잠수, 반잠수 부유구조물에 의한 파의 비선형성을 평가하기 위해서 적용된다. 더우기 부유 구조물 내의 공기압 변화를 고려하기 위하여 Boyle-Charles 법칙에 따른 단열변화를 가정하여 유도된 공기압축모델이 새로이 개발되었다. 가상경계에서 감쇠정상파를 고려한 방법 I의 이론치는 감시정상파의 영향이 미치지 않는 가상 연직경계면을 같는 방법 II의 값과 잘 일치한다. 두 이론에 의한 이론치는 실험치와 잘 일치함을 보여준다.