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Generation of sub-micron (nano) bubbles and characterization of their fundamental properties
Sangbeom Kim,Hyoungjun Kim,Mooyoung Han,Tschungil Kim 대한환경공학회 2019 Environmental Engineering Research Vol.24 No.3
Although nanobubbles attract significant attention, their characteristics and applications have not been thoroughly defined. There are diverse opinions about the definition of nanobubbles and controversy regarding methods that verify their characteristics. This study defines nanobubbles as having a size less than 1 μm. The generation of these sub-micron (nano) bubbles may be verified by induced coalescence or light scattering. The size of a sub-micron (nano) bubbles may be measured by optical, and confocal laser scanning microscopy. Also, the size may be estimated by the relationship of bubble size with the dissolved oxygen concentration. However, further research is required to accurately define the average bubble size. The zeta potential of sub-micron (nano) bubbles decreases as pH increases, and this trend is consistent for micron bubbles. When the bubble size is reduced to about 700-900 nm, they become stationary in water and lose buoyancy. This characteristic means that measuring the concentration of sub-micron (nano) bubbles by volume may be possible by irradiating them with ultrasonic waves, causing them to merge into micron bubbles. As mass transfer is a function of surface area and rising velocity, this strongly indicates that the application of sub-micron (nano) bubbles may significantly increase mass transfer rates in advanced oxidation and aeration processes.
국내06/북미ULEV-II 대응 촉매장치 강건설계 최적화 연구
김상범(Sangbeom Kim),김성근(Sungkun Kim),장한수(Hansoo Chang),김홍집(Hongjip Kim),연태헌(Taehun Yeon) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
The conventional aftertreatment systems to meet the stringent ULEV-Ⅱ emission regulation are usually composed of warm-up catalytic converter (WCC) and underfloor catalytic converter (UCC). However, those systems bring high cost, high back pressure, the limit of engine room for package design, and other side effects. The new optimized system needs to solve these problems and to meet ULEV-Ⅱ emission regulation efficiently. There are many technologies and design parameters in exhaust catalytic converter systems ; exhaust manifold structure, exhaust gas flow distribution, location of catalytic converter, PM coating technologies, substrate characteristics, and volume of catalysts. It is a key factor to make a optimized robust system with those parameters and technologies described. The new optimized exhaust and Integrated Close-coupled Catalytic Converter (ICCC) system can meet ULEV-Ⅱ regulation and can solve those problems of conventional system by a robust design. This study was focused on the optimization process of exhaust and ICCC system to determine robust design control factors, which are durability of catalyst - aged and/or fresh - , by vehicle evaluation, FTP-75.