• Water Engineering Research
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• 제4권3호
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• pp.127-139
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• 2003

This paper presents the hydraulic analysis of the oxygen transfer through the air entrainment and the relationships between the efficiency of the oxygen transfer and the hydraulic parameters in the riparian riffles. Field survey on the pool-riffle formation of the river reach and the measurements of the oxygen transfer in the riffles were performed. Air entrainment occurred more frequently in the edged gravels rather than in the round and edgeless ones, and it was formed mainly from behind the trailing edges of the gravels. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number, but to be not closely related to the particle diameter. Average value of oxygen transfer in the riffles of study area was about 0.085, which shows good efficiency compared with results of smooth chute. Variation of the water level, which increases in proportion to the flow velocity and the flow discharge, seems to make the air entrainment more active, but has not been verified quantitatively. Relationships between the air entrainment and the variation of the water level must be considered in the further study.

• 자원리싸이클링
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• 제28권6호
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• pp.73-78
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• 2019

본 연구에서는 활성 슬러지 하수처리장에서 배출되는 off-gas에 대한 포집 및 측정 모니터링을 통해 폭기조의 산소전달효율을 측정하고 청수와 비교하여 시스템의 신뢰성을 검증하는 연구를 수행하였다. 먼저, 청수를 기반으로 용존산소, 산소전달계수 및 표준산소전달효율을 측정하였으며 각각 8.60 mg/L, 9.49/hr, 23.96%의 값이 얻어졌다. 한편, 하수처리장 현장에서 진행한 off-gas 시험 결과 표준산소전달효율이 22.81%로 계산되어 청수와의 차이가 거의 없는 것으로 나타났다. 이는 현장에 설치된 산기관의 성능 및 폭기조의 상황을 모니터링 시스템을 이용해 실시간으로 확인함으로써 신뢰성있는 데이터를 확보할 수 있음을 의미한다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.604-608
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• 2004

Experimental study was conducted to increase the oxygen transfer efficiency of air diffusers in clean water. By measuring the bubble size from the bubbly two-phase flow visualization with several air diffusers the size of air bubbles near the top surface of aeration tank seems to be independent on the diffuser types. Considering design parameters for the better breakup of larger bubbles around the air diffusers, advanced conceptual air diffusers using nozzle-type throat showing the higher oxygen transfer efficiencies were made.

• International Journal of Fluid Machinery and Systems
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• 제5권1호
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• pp.10-17
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• 2012

The objective of this study was to investigate the oxygen transfer characteristics of an ejector aeration system. In order to evaluate the oxygen transfer performance of the ejector aeration system, a comparative experiment was conducted on a conventional blower aeration system. The effect of entrained air flow rate and aerating water temperature on the oxygen transfer efficiency was investigated. The dissolved oxygen concentration increased with increasing entrained air flow rate, but decreased with increasing aerating water temperature for two aeration systems. The volumetric mass transfer coefficient increased with increasing entrained air flow rate and with increasing aerating water temperature for both aeration systems. The average mass transfer coefficient for the ejector aeration system was about 20% and 42% higher than that of the blower aeration system within the experimental range of entrained air flow rates and aerating water temperatures.

• Journal of Ceramic Processing Research
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• 제20권1호
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• pp.18-23
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• 2019

Chemical looping combustion (CLC) is a promising carbon capture and storage (CCS) technology whose efficiency and cost primarily relies on the oxygen carrier materials used. In this paper, gadolinium-doped ceria (GDC, Ce0.9Gd0.1O1.95) was added as a promoter to improve the oxygen transfer rate of MgMnO3-δ oxygen carrier materials. Increasing GDC content significantly increased the oxygen transfer rate of MgMnO3-δ-GDC composites for the reduction reaction due to an increase in the surface adsorption of CH4 via oxygen vacancies formed on the surface of the GDC. On the other hand, the oxygen transfer rate for the oxidation reaction decreased linearly with increasing GDC content due to the oxygen storage ability of GDC. Adsorbed oxygen molecules preferentially insert themselves into oxygen vacancies of the GDC lattice rather than reacting with (Mg,Mn)O to form MgMnO3-δ during the oxidation reaction.

• 한국수산과학회지
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• 제30권3호
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• pp.451-458
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• 1997

The oxygen transfer coefficient was not significantly affected by either flow pattern, initial bubble size or the wastes present in the water studied. Surface active substances in the water did however influence the transition from bubble to slug flow. Airlift with length to diameter ratios less than 50 suffered from considerable losses in efficiency. When properly designed, airlift pumping efficiencies were comparable to those of conventional centrifugal pumps and the oxygen transfer efficiency were as high as or higher than those of diffused aeration systems.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1332-1335
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• 2003

This paper presents the enhancement of oxygen transfer efficiency using the vibrating intravascular lung assist device (VIVLAD) in in-vitro experiments for patients having chronic respiratory problems. The test section was a cylinder duct with the inner diameter of 30 mm. The flow rate was controlled by the pump and monitored by a built-in flow meter. The vibration apparatus was composed of a piezo-vibrator, a function generator. and a power amplifier. The direction of vibration was radial to the fluid flow. Gas flow rates of up to 6 l/min through the 120-cm-Jong hollow fibers have been achieved by exciting a piezo-vibrator. The output of PVDF sensor were investigated by various frequencies in VIVLAD. The experimental results showed that VIVLAD would be enhance oxygen transfer efficiency.

• 한국물환경학회지
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• 제22권6호
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• pp.1119-1122
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• 2006

Aeration by using diffusers usually requires approximately 50~90% of the total electricity needed to operate WWTP (WasteWater Treatment Plant)s. Accurate evaluation of the oxygen transfer efficiency for an aeration system, and recommendation of a better alternative may help saving WWTP operational costs. Appropriate techniques and methods to achieve this purpose have not been introduced in Korea. In this study, in-process analysis was performed for a coarse bubble aeration system by the off-gas method to evaluate its applicability in Korea. To accomplish this analysis, an off-gas test, unsteady-state clean water test and steady-state off-gas column test was conducted and comparisons to other aeration systems were made. The ${\alpha}$ and the F estimated from the results of the unsteady-state clean water test and the steady-state off-gas column test were 0.61 and 0.90 respectively in a coarse bubble aeration system. The comparison of P.E tube diffusers laid out single spiral roll and ceramic dome diffusers laid out full floor coverage showed that the oxygen transfer efficiency of the coarse bubble aeration system was less than or similar to other aeration systems. But, airflow rates per unit area were 4~5 times greater than other aeration systems. In regards to the oxygen transfer efficiency for airflow rates per unit area, a retrofit to higher efficiency diffusers was urgently needed. This study showed proved that off-gas methods can apply to evaluate diffuser performances to estimate operating factors and to compare other aeration systems in Korea.

• 한국유체기계학회 논문집
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• 제8권5호
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• pp.7-12
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• 2005

Experimental study was conducted to increase the oxygen transfer efficiency of air diffusers in clean water. By measuring the bubble size from the bubbly two-phase flow visualization with several air diffusers, the size of air bubbles near the top surface of aeration tank seems to be independent on the diffuser types. Considering design parameters for the better break-up of larger bubbles around the air diffusers, advanced conceptual air diffusers using nozzle-type throat showing the higher oxygen transfer efficiencies were made.

• Bulletin of the Korean Chemical Society
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• 제22권1호
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• pp.63-67
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• 2001

The photophysical properties and the singlet oxygen generation efficiency of tetrathiarubyrin have been investigated to elucidate the possibility of its use as a photodynamic therapy (PDT) photosensitizer by steady-state and time-resolved spectroscopic methods. The observed photophysical properties were affected by various molecular aspects, such as extended ${\pi}conjugation$, structural distortion, and internal heavy atom. The steady-state electronic absorption spectrum was red-shifted due to the extended $\pi-conjugation$, and the spin orbital coupling was enhanced by the structural distortion and the internal heavy atom effect. As a result of the enhanced spin orbital coupling, the triplet quantum yield increased to 0.90 $\pm$ 0.10 and the triplet state lifetime was shortened to 7.0 $\pm$ 1.2 ${\mu}s$. Since the triplet state decays at a relatively faster rate, the efficiency of the oxygen quenching of the triplet state decreases. The singlet oxygen quantum yield was estimated to be 0.52 $\pm$ 0.02, which is somewhat lower than expected. On the other hand, the efficiency of singlet oxygen generation during the oxygen quenching of triplet state, $f{\Delta}^T$, is near unity. Such high efficiency of singlet oxygen generation can be explained by the following two possible factors: The hydrogen bonding of ethanol which impedes the deactivation pathway of the charge transfer complex with oxygen to the ground state, the less probability of the aggregation formation.