• Journal of the KSME
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• v.35 no.9
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• pp.836-847
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• 1995

파울링은 열교환기에 형성되는 열저항으로 에너지 손실에 많은 영향을 미친다. 그러나 파울링은 그 예측이나 감소 또는 제거가 매우 어려운 것으로 인식되어 왔다. 작동유체자체를 철결하게 유지함으로써 파울링을 감소할 수도 있으나 작동유체 자체의 특성 때문에 본질적으로 작동유체를 청결하게 유지할 수 없는 경우가 대부분이다. 즉, 폐열 회수의 대상이 되는 액체가 하천수나 생 활하수인 경우 작동액체를 청결하게 유지함으로써 파을링을 저감시피는 방법은 타당치 않다.일 본의 폐얼회수 프로젝트와 담수화 프로젝트에서 특이한 점은 두 가지 프로젝트에서 열교환기면의 파울링 문제 해경을 전열 촉진의 내용과 거의 비슷한 비중으로 다루고 있다는 점이다. 파울링은 오래 전부터 열시스템설계자의 주요 관심사였으나 큰 진전은 없었다. 그러나 현재는 주변기술이 발달로 더 이상 연구 불가능 영역은 아닐 듯 싶다.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.31.1-31.1
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• 2005

• 기계와재료
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• v.14 no.2 s.52
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• pp.108-118
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• 2002

• Journal of Korean Society of Environmental Engineers
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• v.22 no.7
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• pp.1183-1191
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• 2000

Operating conditions for reduction of membrane fouling in treatment of dissolved organic matter by UF membrane process were investigated by pilot-scale plant using various operating conditions. As inlet pressure increased, increament of transmembrane pressure and flux decline were faster. The reason was due to the increase in adsorption of dissolved organic matter and the development of cake layer compression on the membrane surface. When efficient pressure (the difference of pressure between backwash and transmembrane pressures) was high, small amount of pollutant was retained on the membrane surface. When backwash was frequently conducted, low concentration of pollutant was maintained in recycling water. Therefore, backwash could be efficiently conducted with high efficient pressure and high frequency. Fouling rate was correlated with backwash and inlet pressures, recovery rate and cumulative permeated volume. Among the operating parameters backwash pressure was most closely related to fouling rate and inlet pressure was next to backwash pressure. It seems that the fouling was strongly related to pressure which leads to the cake layer compression and adsorption of dissolved organic matter.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.152-156
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• 2016

Wastewater heat recovery heat pump systems use heated wastewater from public baths or factories as the heat pump's heat source. Generally, this system uses a bare tube evaporator. In the heat transfer process from wastewater to refrigerant, thermal resistance is caused primarily by fouling deposits on the outside surface of tube. Fouling directly increases thermal resistance and decreases heat pump efficiency. Thus, it is desirable to eliminate fouling. In this study, we fabricated a fouling mitigation device using a bubbling fluidized bed with cleaning sponge balls in the wastewater bath. Experimental conditions were as follows: $20^{\circ}C$ cold-water temperature, $40^{\circ}C$ wastewater temperature, 100 L/h cold water flow rate, and $0.161m^2$ heat exchanger surface area. Experimental results showed that the thermal resistance of fouling decreased by 56% with the fluidized bed alone and by 86% with both the fluidized bed and cleaning sponge balls.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.4
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• pp.330-334
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• 2007

The objective of this study was to investigate the effecs of fouling mitigation for ceramic ball in cooling water system experimentally. The devices filled with ceramic balls were connected to the bypass line of the heat exchanging system. Cooling water in the heat exchanging system was artificial water. To visualize the formation of fouling on the heat transfer surface a number of images were obtained using a CCD camera with real-time microscopy. Fouling resistances and overall heat transfer coefficients were measured in order to analyze fouling mitigation effects. We found that the ceramic ball devices for artificial water reduced the formation of fouling compared to the no-mitigation devices.

• Membrane Journal
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• v.26 no.4
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• pp.273-280
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• 2016

Pressure assisted forward osmosis (PAFO) is recently introduced because of its improved process efficiency to overcome drawbacks of forward osmosis (FO) such as low water flux and reverse solute diffusion. However, it is known that membrane fouling becomes deteriorated by additional hydraulic pressure applied in PAFO compared to FO. This study was performed to investigate possibility of intermittent pressure-assisted forward osmosis (I-PAFO) operation for fouling mitigation using colloidal silica particles as model foulants. FO, PAFO were operated as well to compare with. Two different solution pH conditions (pH 3, 10) were applied to see the effect of electrostatic interactions between the membrane and silica particles on fouling tendency. In the results, higher water flux was observed during pressurization and pressure relaxation periods in I-PAFO than water flux of PAFO, and FO on both pH conditions. Water flux decreased less in I-PAFO than PAFO after fouling. It resulted in higher water flux recovery in I-PAFO than PAFO after physical cleaning.

• Clean Technology
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• v.29 no.1
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• pp.31-38
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• 2023

Due to water shortages caused by water pollution and climate change, total organic carbon (TOC) standards have been implemented for wastewater discharged from public sewage treatment facilities. Furthermore, there is a growing interest and body of research pertaining to the reuse of sewage treatment water as a secure alternative water resource. The membrane bio-reactor (MBR) method is commonly used for advanced wastewater treatment because it can remove organic and inorganic ions and it does not require or emit any chemicals. However, the MBR process uses a separation membrane (MF), which requires frequent film cleaning due to fouling caused by a high concentration of mixed liquor suspended solid (MLSS). In this study, process improvement and microbubble cleaning efficiency were evaluated to improve the differential pressure, water flow, and MF fouling, which are the biggest disadvantages of operating the MF. The existing MBR method was improved by installing a precipitation tank between the air tank and the MBR tank in which raw water was introduced. Microbubbles were injected into a separation membrane tank into which the supernatant water from the precipitation tank was introduced. The microbubble generator was operated with a 15 day on, 15 day off cycle for 5 months to collect discharged water samples (4L) and measure TOC. As the supernatant water from the precipitation tank flowed into the separation membrane tank, about 95% of the supernatant water MLSS was removed so the MF fouling from biological contamination was prevented. Due to the application of microbubbles to supernatant water from the precipitation tank, the differential pressure of the separation membrane tank decreased by 1.6 to 2.3 times and the water flow increased by 1.4 times. Applying microbubbles increased the TOC removal rate by more than 58%. This study showed that separately operating the air tank and the separation membrane tank can reduce fouling, and suggested that applying additional microbubbles could improve the differential pressure, water flow, and fouling to provide a more efficient advanced treatment method.

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.51-56
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• 2011

This study was conducted to investigate the applicability of pulsed electric field (PEF) treatment for the prevention of scaling formation and membrane fouling reduction. To validate the effect of PEF and to identify the mechanism, some experiments with and without PEF treatment were carried out. PEF treatment affected the precipitation of $CaCO_3$ by which $CaCO_3$ particles were actively grown and sedimented. It was confirmed that the calcium ions were decreased as 78% and particle size was grown by PEF treatment. It was also verified that the crystalline structure of $CaCO_3$ was transformed by PEF treatment from Aragonite, which is formed at a high temperature and hard to be removed, to Calcite being stable at room temperature. In PEF treatment, permeate volume and permeation flux were greater than that of without PEF, case while Langelier Index(LI) decreased. From the experiment results, PEF treatment is believed to be an effective method to prevent scaling formation and to mitigate $CaCO_3$ fouling as the pretreatment of membrane filtration.

• Membrane Journal
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• v.14 no.1
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• pp.66-74
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• 2004

Total resistance of membrane in a micro-filtration system using a metal membrane was mainly attributed to the permeate resistance of cake layer($R_c$), which was formed by deposited particles from the physico-chemical interactions of solids on membrane surface. Intermittent back ozonation was highly effective than the air backwashing for fouling reduction. As far the operational effect, under same ozone injection, the increase of gas flow-rate was more favorable than the increase of injection time far the recovery of permeation flux. As the filtration time was longer, the effect of flux recovery by intermittent back-ozonation decreased. Therefore, it is preferable to operate membrane cleaning before the foulant is consolidated on membrane surface.