• 멤브레인
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• 제25권3호
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• pp.268-275
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• 2015

침지식 분리막 모듈에서 공기강도에 따른 분리막 위치에 대한 오염을 조사하였다. 분리막의 충진밀도가 낮은 곳에서 높은 유체 유속을 나타내었으며, 유체 속도는 기-액 주입률에 비례하였다. 전단응력은 기-액 주입률 및 유체 유속에 비례하였다. 비가역오염($R_{ir}$)은 흡입 압력이 가까운 부분에서 가장 높게 나타났다(position 1). 비가역오염에 대한 저항과 분리막 고유 저항의 비($R_{ir}/R_m$) 및 비가역오염에 대한 저항과 가역오염의 저항의 비($R_{ir}/R_r$)도 position 1에서 가장 높게 조사되었다. 비가역오염($R_{ir}$)은 흡입 압력이 높은 곳인 position 1에 오염물질이 축적되어진 결과이다. 분리막 위치에 따른 오염현상은 모듈 디자인 최적화에 중요한 인자임을 알았다.

• 대한기계학회논문집B
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• 제20권11호
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• pp.3695-3705
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• 1996

We designed the hot wind tunnel to reproduce the conditions of utility boiler and carried out its performance test, in order to investigate the particulate two-phase flow behaviour, the fouling and heat transfer characteristics to the heat exchanger. The hot wind tunnel introduces the control system to control the temperature in the test section. The particle is injected into the hot gas stream. The fouling probe (cylindrical tube) is positioned normal to the particulate gas-particle two-phase flow and cooled by the air. The temperature of gas and cooling air, and temperature in the fouling probe are measured as a function of time, giving the local and averaged heat transfer and fouling factor. The shape of particulate deposition adhered to the fouling probe is also observed.

• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.131-139
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• 1999

An experimental study was conducted to investigate the fouling effects of geothermal water scale deposited onto a heating surface upon its forced convection heat transfer characteristics. Scales deposited onto the heating surfaces of heat exchangers seriously reduce the heat transfer perfor-mance and also increase the hydrodynamic drag. Accordingly fouling is an important problem in the design and operation of heat exchangers. The cylinders were settled in tandem with equal dis-tance between neighbouring cylinders and only the test cylinder was heated under the condition of constant heat flux. The Reynolds number was varied from 13000310 through 50003100. It is found that the heat transfer of the in-line tube banks greatly varies with the fouling of geothermal water scale especially its scale height. Further the local and average Nusselt numbers strongly depend upon the cylinder spacing and the Reynolds number.

• Journal of Advanced Marine Engineering and Technology
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• 제34권2호
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• pp.235-242
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• 2010

본 연구는 열교환기의 가열된 표면위에 부착된 지열수 스케일의 조도 영향을 검증하기 위한 강제 대류 열전달에 관한 실험적 연구이다. 실험은 원형 원관 위에 5종류의 실리카 스케일 입자를 균일하게 부착하여 행하였다. Reynolds수는 13,000에서 50,000의 범위에서 행하였다. 국소와 평균 열전달 특성은 스케일 입자 크기와 레이놀즈수의 함수로서 측정하였으며 평균오염저항을 이들의 결과로부터 평가하고 그들의 특성들을 분석 하였다. 원관의 열전달 특성은 지열수 스케일의 오염에 의해, 특히 입자 크기에 의해 크게 변화하였다. 또한 국소와 평균 Nusselt수는 원관 간격과 Reynolds 수에 의해 크게 의존 되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.61-66
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• 2003

Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator.

• 대한기계학회논문집B
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• 제24권11호
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• pp.1478-1485
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• 2000

An experimental study has been performed to investigated the forced convection heat transfer characteristics of 6 circular cylinders in staggered arrangement in a cross flow of air. The water scale deposited on condenser wall of power plant was used to investigate the effect of roughness of scaled surfaces. The relative roughness*average diameter of scale/cylinder diameter) was in a range of k/d=0.0066, 0.0111, 0.0167, 0.0222 and 0.0278. The cylinder spacings(L/d) varies from 1.5 to 4.0 where L denote the cylinder spacings along and normal to the upstream uniform flow direction. The Reynolds number was varied in a range of 10, 000$\leq$ Re $\leq$ 50,000. The local and mean Nusselt numbers were investigated as a function of scale roughness, the cylinder spacing and Reynolds number. The results are compared with those of clean cylinder and inline tube bank, subsequently the mean fouling resistance over the entire circumference was estimated from those results as a function of scale roughness, the cylinder spacing and Reynolds number.

• Membrane and Water Treatment
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• 제6권1호
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• pp.15-26
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• 2015

The compact structure and high-quality effluent of membrane bioreactors make them well-suited for decentralized greywater reclamation. However, the occurrence of membrane fouling continues to limit their effectiveness. To address this concern, a unique membrane module configuration was developed for use in a decentralized greywater treatment system. The module featured local aeration directly below a series of inclined membrane bundles, giving the overall module a twisted appearance compared to a module with vertically orientated fibres. The intent of this design was to increase the frequency and intensity of collisions between rising air bubbles and the membrane surface. Material related to the construction of custom-fit modules is rarely communicated. Therefore, detailed design and assembly procedures were provided in this paper. The twisted module was compared to two commercially available modules with diverse specifications in order to assess the relative performance and marketability of the twisted module with respect to existing products. Contaminant removal efficiencies were determined in terms of biochemical oxygen demand, chemical oxygen demand, ammonia, total nitrogen, total phosphorus, and turbidity for each module. Membrane fouling was monitored in terms of permeate flux, transmembrane pressure, and membrane resistance. Following 168 h of operation, the twisted module configuration demonstrated competitive performance, indicating good potential for further development and commercialization.

• Membrane and Water Treatment
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• 제1권4호
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• pp.283-296
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• 2010

During the disinfection of potable water, humic substances present in the solution react with chlorine to form potential carcinogenic compounds. This study evaluates the feasibility of using a submerged membrane photocatalysis reactor (SMPR) process for treatment of humic substances through the characterization of both organic removal efficiency and membrane hydraulic performance. A simple SMPR was operated and led to the removal of up to 83% of the polluting humic matters. Temporal rates of organic removal and membrane fouling were found to decrease with filtration time. Using tighter membrane in the hybrid process resulted in not only higher organic removal, but also more significant membrane fouling. Under the experimental conditions tested, optimum $TiO_2$ concentration for humic removal was found to be 0.6 g/L, and increasing initial pollutant concentration expectedly resulted in a more substantial membrane fouling. The importance of the influent nature and pollutant characteristics in this type of treatment was also assessed as various water sources were tested (model humic acid solution vs. local water containing natural organic matters). Results from this study revealed the promising nature of the SMPR process as an alternative technique for organic removal in the existing water treatment system.

• 해양환경안전학회지
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• 제28권6호
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• pp.1078-1085
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• 2022

선박에 부착된 수중생물은 선체에서 성장하면서 선박의 저항을 크게 증가시킬 뿐만 아니라 부착생물이 배와 함께 이동하면서 지역의 해양 생태계 교란을 야기시키기도 한다. 이에 따라 국제해사기구에서는 선체부착생물의 이동을 막기 위해 선체부착생물 제거 및 청소성능 평가 논의를 시작해 오고 있다. 본 연구에서는 소형선박에 사용되는 FRP(Fiber Reinforced Plastic), HDPE((High Density Polyethylene), CFRP(Carbon Fiber Reinforced Plastic) 재료의 시편을 격포항(전락북도)에 약 80일간 양생시킨 후 물 제트 노즐을 이용하여 부착생물 제거실험을 수행하였다. 그 결과 김과 같은 해조류는 노즐과 시편과의 거리가 1.8cm, 100bar 일 때 제거되었지만, 따개비의 경우 200 bar 이상은 되어야 청소가 되는 것을 확인하였다.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3164-3182
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• 2023

The CRUD on the fuel cladding under the pressurized water reactor (PWR) operating condition causes several issues. The CRUD can act as thermal resistance and increases the local cladding temperature which accelerate the corrosion process. The hideout of boron inside the CRUD results in axial offset anomaly and reduces the plant's shutdown margin. Recently, there are efforts to revise the acceptance criteria of emergency core cooling systems (ECCS), and additionally require the modeling of the thermal resistance effect of the CRUD during the performance analysis. There is an urgent need for the evaluation of the effect of the CRUD deposition on the cladding heat transfer under PWR operating conditions, but the experimental database is very limited. The experimental facility called DISNY was designed and constructed to analyze the CRUD-related multi-physical phenomena, and the performance analysis of the constructed DISNY facility was conducted. The thermal-hydraulic and water chemistry conditions to simulate the CRUD growth under PWR operating conditions were established. The design characteristics and feasibility of the DISNY facility were validated by the MARS-KS code analysis and separate performance tests. In the current study, detailed design features, design validation results, and future utilization plans of the proposed DISNY facility are presented.