• 분석과학
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• 제31권1호
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• pp.14-22
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• 2018

After signing the WHO FCTC in 2003, South Korea ratified the FCTC in 2005. This study was conducted to provide data on toxic constituents that can be used as useful information for the level of exposure to Korean smokers. Emissions data from five brands of cigarettes were tested under the ISO and "Canadian Intense (HCI)" smoking regimes, respectively. We conducted an analysis of 25 compounds containing nicotine, tar, carbonyls, phenolics, volatile organic compounds (VOCs), and semi-VOC cigarette smoke. Tar and nicotine showed levels of 4.3 to 5.8 mg/cig and 0.4 to 0.5 mg/cig, respectively, which are within the range of tolerance presented in ISO 8243. In the case of carbonyls, formaldehyde was detected within a range of 8.2 to $14.3{\mu}g/cig$, and acetaldehyde was present within a range of 224.7 to $327.2{\mu}g/cig$ under the ISO smoke regime. Crotonaldehyde was not detected under the ISO regime, and all of the carbonyls showed values 2.3 to 4.5 times higher under the HCI regime than those under the ISO regime. Catechol, which showed a level of 47.0 to $80.5{\mu}g/cig$ under the ISO regime and 117.5 to $184.7{\mu}g/cig$ under the HCI regime, was the highest constituent among the phenols. The amount of isoprene was 91.7 to $158.3{\mu}g/cig$ under the ISO regime and 221.0 to 377.0 under the HCI regime. To summarize, most of the constituents showed a tendency to be detected at levels 2 to 4 times higher under the HCI regime than under the ISO regime. Above all, these results represent the first analysis in Korea from an independent institute of tobacco companies under accreditation of ISO 17025.

• 한국전산유체공학회지
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• 제17권1호
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• pp.86-93
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• 2012

A numerical investigation is conducted to search for the optimal flow rate for a rotating-disk chemical vapor decomposition reactor operating at a high temperature and a low pressure. The flow of a gas mixture supplied into the reactor is modeled by a laminar flow of an ideal gas obeying the kinetic theory. The axisymmetric two-dimensional flow in the reactor is simulated by employing a CFD package FLUENT. With operating pressure and temperature fixed, numerical computations are performed by varying rotation rate and flow rate. Examination of the structures of flow and thermal fields leads to a flow regime diagram illustrating that there are a stable plug-like flow regime and a few unfavorable flow regimes induced by mass unbalance or buoyancy. The criterion for sustaining a plug-like flow regime is discussed based on a theoretical scaling argument. Interpretation of the flow regime map suggests that a favorable flow is attainable with a minimum flow rate at the smallest rotation rate guaranteeing the dominance of rotation effects over buoyancy.

• Korean Chemical Engineering Research
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• 제47권4호
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• pp.481-487
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• 2009

본 연구에서는 기체(공기)-액체(용융탄산염) 이상 흐름계(용융염산화 공정)에서 공기유속(0.05~0.22 m/sec) 및 탄산용융염의 온도($870{\sim}970^{\circ}C$)가 흐름영역 전이특성에 미치는 영향을 공기 체류량의 drift-flux 및 차압요동의 추계학적 해석을 통하여 규명하였다. 흐름영역이 시작되는 공기 체류량값은 공기체류량-drift flux 그래프를 통하여 구하였다. 흐름영역 전이가 시작되는 공기 체류량 값은 탄산용융염의 온도가 증가함에 따라서 증가하였는데 이는 탄산용융염의 온도가 증가함에 따라서 액상의 점도와 표면장력의 감소로 인한 계의 안정화 때문이며 계의 특성에 가장 큰 영향을 미치는 기포특성(평균기포크기 및 상승속도)을 drift-flux 모델식을 적용하여 추정하였다. 흐름영역전이 특성을 좀 더 정량적으로 특성화하기 위하여 차압요동신호를 상공간투영 및 Kolmogorov entropy를 이용하여 해석하였다. Kolmogorov entropy는 탄산용융염의 온도가 증가함에 따라 감소하였으며 공기유속이 증가함에 따라서 증가하였으나 흐름영역에 따라서 다른 경향성을 나타내었고 흐름영역이 시작되는 공기유속값은 공기체류량의 drift-flux 해석으로 유도된 결과와 동일하였다.

• Membrane and Water Treatment
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• 제3권3호
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• pp.151-168
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• 2012

Gas sparging is one of the techniques used to control the concentration polarization during ultrafiltration. In this work, the effects of gas sparging in stratified flow regime were investigated during gel layer controlling cross flow ultrafiltration in a rectangular channel. Synthetic solution of pectin was used as the gel forming solute. The liquid and gas flow rates were selected such that a stratified flow regime was prevalent in the channel. A mass transfer model was developed for this system to quantify the effects of gas flow rates on mass transfer coefficient (Sherwood number). The results were compared with the case of no gas sparging. Gas sparging led to an increase of mass transfer coefficient by about 23% in this case. The limitation of the developed model was also evaluated and it was observed that beyond a gas flow rate of 20 l/h, the model was unable to explain the experimental observation, i.e., the decrease in permeate flux with flow rate.

• Bulletin of the Korean Chemical Society
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• 제24권10호
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• pp.1485-1489
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• 2003

The gelation for di-(2-ethylhexyl) phthalate (DEHP)-plasticized poly(vinyl chloride) was studied by measuring time-resolved small-angle X-ray scattering (SAXS) and a flow of the solutions in test tube. It was found that for the gelation there were three regimes. At Regime I, the solution rapidly changed to a gel, and the SAXS intensity showed a peak and the peak intensity increased, keeping the peak angle constant. Applying the SAXS intensity to the kinetic analysis of the liquid-liquid phase separation, it was revealed that the spinodal decomposition proceeded to develop a periodic length of 29.9 nanometer in size, a hydrogen-bonding-type association in polymer rich phase followed, and then it induced fast gelation rate. At Regime II, the gelation slowly occurred and the SAXS intensity was not observed, suggesting that a homogeneous gel network was formed by a hydrogen-bonding. At regime III, the solution was a homogeneous sol.

• 한국연소학회지
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• 제9권4호
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• pp.35-46
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• 2004

Activation energy asymptotics (AEA) for Linan#s premixed-flame regime is revisited in this paper. First, the detailed AEA procedure for the premixed-flame regime is demonstrated, so that the practitioners of AEA could easily apply the method to their own problems. In addition, the controversies surrounding the premixed-flame regime, namely the closure controversy and fast-time instability paradox, are explained. Finally, the limitation of AEA, mainly arising from the wrong prediction of fuel leakage through the reaction zone, is examined and the Zel#dovich-Linan kinetics is introduced as an alternative to meet the needs of modern combustion analysis, where the detailed chemical structure of flame is demanded.

• Korean Chemical Engineering Research
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• 제52권6호
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• pp.821-825
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• 2014

바이오매스의 수증기 가스화 특성을 고온 영역에서 살펴보고자 열중량 분석기(thermobalance)에서 톱밥 촤의 수증기 가스화 연구를 수행하였다. 반응 온도를 $850^{\circ}C$에서 $1400^{\circ}C$까지 수증기 분압을 0.3, 0.5, 0.7 atm으로 변화시키며 가스화 실험이 수행되었다. 반응 kinetics 해석은 기체-고체 화학반응의 세 가지 모델이 이용되었고 이 중 modified volumetric model이 중량 변화를 가장 잘 나타내었다. 가스화 온도 $900^{\circ}C$를 기준으로 diffusion control regime과 reaction control regime의 두 단계로 가스화가 구분되었으며 이때 각각의 regime에 대하여 활성화에너지와 빈도인자를 도출하고 수증기 분압의 영향을 살펴보았다. 가스화와 동시에 수성가스화 변환반응이 진행되어 생성기체의 $H_2$ 농도가 CO에 비하여 2배 정도 높은 값을 나타내었다.

• Korean Chemical Engineering Research
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• 제59권4호
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• pp.626-631
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• 2021

전기투석장치, 전기화학 전지, 미세유체역학 분석 장치 등에서 사용하는 이온 교환 막 근처의 대표적인 비선형 전기동역학 현상은 전기와류 불안정성이다. 전기투석 장치에서 전기와류 불안정성은 물질 전달 속도 증폭을 통해 물질 전달에 대한 이점을 제공한다. 그러나 전기화학 전지나 미세유체역학 장치에서 발생하는 불안정성은 원치 않는 물질 전달 기작을 유발시킨다. 본 연구에서는 전기와류 불안정성의 제어하기 위해, 인가 전압과 공간 제약 효과의 전기와류 불안정성에 대한 영향을 연구하였다. 그 결과, 인가 전압과 공간 제약의 정도에 따라 불안정성의 동역학이 안정 영역 - 고정 영역 - 혼돈 영역 순으로 전이됨을 밝혀내었다. 더불어, 동역학 전이에 대한 안정성 곡선을 수치적으로 결정하였다. 결론적으로, 공간 제약 효과는 전기동역학적 혼돈을 제어할 수 있는 효과적인 기작으로 활용 가능할 것이다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.83-86
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• 2015

The Laminar lifted methane jet flames diluted with helium and nitrogen in co-flow air have been investigated experimentally. The chemiluminescence intensities of $OH^{\ast}$ and $CH_2O^{\ast}$ radicals and the radius of curvature for tri-brachial flame were measured using an intensified charge coupled device (ICCD) camera, monochromator and digital video camera. The product of $OH^{\ast}$ and $CH_2O^{\ast}$ is used as a excellent proxy of heat release rate. These methane jet flames could be lifted in buoyancy and jet dominated regimes despite the Schmidt number less than unity. Lifted flames were stabilized due to buoyancy induced convection in buoyancy-dominated regime. It was confirmed that increased $OH^{\ast}$ and $CH_2O^{\ast}$ concentration caused an increase of edge flame speed via enhanced chemical reaction in buoyancy dominated regime. In jet momentum dominated regime lifted flames were observed even for nozzle exit velocities much higher than stoichiometric laminar flame speed. An increase in radius of curvature in addition to the increased $OH^{\ast}$ and $CH_2O^{\ast}$ concentration stabilizes such lifted flames.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.217-217
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• 2009

In this work, the oxidation-induced characteristics of five nuclear graphites (NBG-17, NBG-18, NBG-25, IG-110, and IG-430) were studied. The oxidation characteristics of nuclear graphites were measured at the three temperature areas (300, 600, and $900^{\circ}C$). As experimental results, the pore size of oxidized graphite was increased with increasing of oxidation time. It was also found that the oxdation rate was propotional to the oxidation temperature and time. This was probably due to the oxidation was occurred on the surface and inner bulk phase of nuclear graphites at the same time by the socalled chemical regime.