• International Journal of Air-Conditioning and Refrigeration
• /
• 제11권3호
• /
• pp.140-149
• /
• 2003

In these days, environmental concerns have been increased throughout the industry and community worldwide. To prevent the ozone depletion, ozone depletion potential of a refrigerant must be zero. Simultaneously, a refrigerant with low GWP (global warming potential) is very demanding to reduce green house effect. Chlorine-free HFC-l34a is a refrigerant widely used for automotive air-conditioning system because its destruction potential is ecologically zero. Although HFC-l34a has no ozone depletion potential, its global warming potential is so high that it is not considered as a perfect alternative refrigerant that is acceptable for long-term use. In this paper, experimental measurement has been carried out to analyze the performance characteristics of automotive air-conditioning system using HFC-152a, which has low GWP and zero ODP. Also mixed refrigerant that is composed of HFC-152a and $CF_3$ was applied to investigate an alternative possibility for the automotive air-conditioning system. As a result of this study, we could draw following conclusions; With respect to the variation of the rotational speed of compressor, outside air temperature and flow rate, the heat amount of evaporator and compressor and performance coefficient was varied.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
• /
• pp.213-213
• /
• 2011

Gold catalysts supported on TiO2 have shown a unique catalytic behavior on CO oxidation, depending on surface effects. Particle size has an influence on the surface activity. To make monodisperse Au nanoparticles, organic capping ligands, such as alkylthiols, were used by a "greener" synthesis method [1,2] and Au nanoparticles were deposited on TiO2. However, organic capping ligands must be removed for high catalytic activities by the Au nanoparticles without changing the Au size [3]. We used UV ozone treatment to decompose thiol ligands. The samples have been characterized by X-ray photoelectron spectroscopy to examine the surface modification by UV ozone treatment. We show the size distribution of the gold nanoparticles by light scattering analysis and transmission electron microscopy. Au/TiO2 have been prepared using the wetness impregnation method. The catalytic performance of CO oxidation over Au supported on TiO2 under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) were tested. The results show that the catalytic activity depends on particle size and the time of UV ozone exposure, which suggests the role of sulfur bonding in determining the catalytic activity of Au/TiO2 catalysts.

• Journal of Korean Society for Atmospheric Environment
• /
• 제15권E호
• /
• pp.55-64
• /
• 1999

The CIT(California Institute of Technology) three-dimensional Eulerian photochemical model was applied to the Greater Seoul Area, Korea for July 24, 1994, a day of the 9-day ozone episode to understand the characteristics of photochemical air pollution problems in the area. The modeling domain was 60km$\times$60km with the girl size of 2km$\times$2km. As the base case emissions, air pollutant emission data of the National Institute of Environmental Research, Korea for the year of 1991 were used with modifications based on EKMA(Empirical Kinetic Modeling Approach) resutls. Comparisons between predicted and observed concentrations showed that the model predicted the peak concentration over the domain reasonably. It was found that the location of the peak ozone concentration was mainly decided by metorological conditions. But the model could not resolve the spatial variations of concentration station by station, which was mainly caused by localized variations in emission and meteorology.

• 한국환경과학회지
• /
• 제1권1호
• /
• pp.19-33
• /
• 1992

The high oxidants, which occur the daily maximum concentrations in the afternoon, are transported into the other region via long range transport mechanisms or trapped within the shallow mixing boundary layer and then removed physically (deposition, transport by mountain wind, etc.) and chemically (reaction with local sources). Therefore, modeling formation of photochemical oxidants requires a complex description of both chemical and meteorolog ital processecs . In this study, as a part of air quality studies, we reviewed various aspects of photochemical modeling on the basis of currently available literature. The result of the review shows that the model is based on a set of coupled continuity equations describing advection, diffusion, transport, deposition, chemistry, emission. Also photochemical oxidant models require a large amount of input data concerned with all aspects of the ozone life cycle. First, emission inventories of hydrocarbon and nitrogen oxides, with appropriate spatial and temporal resolution. Second, chemical and photochemical data allowing the quantitative description of the formation of ozone and other photochemically-generated secondary pollutants. Third, dry deposition mechanisms particularly for ozone, PAN and hydrogen peroxide to account for their removal by absorption on the ground, crops, natural vegetation, man-made and water surfaces. Finally, meteorological data describing the transport of primary pollutants away from their sources and of secondary pollutants towards the sensitive receptors where environmental damage may occur. In order to improve our present study, shortcomings and limitation of existing models are pointed out and verification Process through observation is emphasized.

• 공업화학
• /
• 제32권4호
• /
• pp.483-486
• /
• 2021

Catalytic ozonation of methyl ethyl ketone (MEK) has been examined over mesoporous MnO_x/Al₂O₃ (MA) catalysts developed by a solvent deficient method using two different manganese precursors including manganese chloride (C) and manganese sulfate (S) at room temperature. The maximum catalytic activities of MA with C (MEK removal efficiency and ozone decomposition of 98.4 and 93.7%, respectively) were higher than those of MA with S (MEK removal efficiency and ozone decomposition of 96 and 68%, respectively). Also the catalytic stability of MA with C was much higher than that of MA with S. The physico-chemical properties of catalysts are well correlated with the activity results, which confirmed that fine dispersion of MnO_x species with high ratios of Mn³⁺/Mn⁴⁺ and more acid sites are attributed to the higher catalyst stability for the MA-C catalyst.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2344-2347
• /
• 2007

To generate negative ion, a small dielectric barrier discharge (DBD) plasma reactor was used in this study and operated by high AC voltage. With increasing of voltage, we can get more negative ions. However unfortunately, if the input voltage is too high, it will also cause formation of ozone which is very harmful to human being health. So the work of finding out the best condition of Voltage and frequency was carried out firstly. After several times of measurement, operating at 20 kHz frequency is the best condition generating high ion concentration without ozone. For the purpose of finding out the best reactor structure, two types of surface dielectric barrier discharge (DBD) reactors were examined to produce negative oxygen ions at the conditions of 20 kHz frequency. The results indicated that the surface DBD reactor with several small tips showed better characteristics for generation of negative oxygen ions at the same condition.

• 대한화학회지
• /
• 제42권2호
• /
• pp.161-171
• /
• 1998

알켄-오존 반응에서 생성된 중간 생성물로써 primary ozonide (POZ),secondary ozonide (SOZ)그리고 carbonyl oxide의 분자구조, vibrational frequencies그리고 infrared(IR)스펙트럼의 세기 등에 대한 이론적 연구를 high level ab initio 양자역학적 방법(CISD,CCSD)을 사용하여 수행하였다. 일반적으로, polarization function은 결합각과 결합길이를 감소시키는 경향을 보였고 반면, electron correlation effect는 결합길이와 결합각을 약간 증가시키는 경향을 보이고 있다. Carbonyl oxide의 분자구조는 zwitterionic form이 diradical form보다 더 안정한 것으로 예측되었으며, 두 형태의 에너지는 차이는 TZ2P CISD level에서 약 22.4 kcal/mol인 것으로 계산되었다. 또한, POZ과 SOZ의 분자구조 및 harmonic vibrational frequencies들을 실험결과와 비교 분석하였으며 IR세기에 근거하여 각 vibrational mode를 assign 하였다.

• 한국대기환경학회지
• /
• 제17권1호
• /
• pp.39-50
• /
• 2001

The spatial distribution characteristics of airborbe mercury(Hg) were investigated used its concentration data from six measurement sites selected to represent:(1) three terminal sites with heavy traffic loads in urban area, (2) one urban residential site and (3) two mountainous sites in Korea. The measurement data obtained during September 1997 through May 1998 indicated that the mean concentration of Hg from different study sites were comparably high with the mean values spanning from 5-9ng./㎥. The concentration from all those sites were systmatically high compared to those of most background sites around world or to other Korean sites investigaed previously. When results of correlation analysis between Hg and relevant parameters were compared among different study sites. temperature was most frequently found out to be in strong correlation with Hg concentrations. Results of factor analysis also indicated that Hg concentrations could be affected simultaneously by th factors affecting such parameters as ozone, temperature, ozone, carbon monoxide, and PM. The findings of enhanced Hg levels from Ji-Ri Mountain relative to terminal site suggest that is distributions may be rather homogeneous not enough to clearly distinguish areal differences and the associated source signatures between urban and rural area. The existence of systmatically high concentrations from all investigated sites also indicate that the impact of its source processes should be quite ubiquitous, while highly variable in relatively long term scale.

• 한국과학교육학회지
• /
• 제19권4호
• /
• pp.585-594
• /
• 1999

The purpose of this study is to examine the concept of Greenhouse Effect as understood by middle school high school university students using a closed-form questionnaire. Based on results of the questionnaire which was administered to 619, the extent to which alternative concepts were held was quantified and compared the difference of various group based on grade level. gender, text and major. Also, subjects were divided into two groups, one is middle school students and the other is high school university students and common themes within conceptual framework of each group were identified by factor analysis. The result showed that students confused Greenhouse Effect with ozone layer depletion in stratosphere and linked familiar contamination around everyday life. acid rain. radioactive contamination, nuclear arsenal to Greenhouse Effect. These trends were more appreciable in female than male, biology major than any other major and text did not make any significant difference. In addition, the result of factor analysis showed that two groups linked familiar contamination around everyday life to Greenhouse Effect and high school university students understand the consequences of an increase in the Greenhouse Effect more systematically than middle school student, perceived the relation between the origin of an increase in the Greenhouse Effect and human activity but confused Greenhouse Effect with ozone layer depletion in stratosphere.

• 한국산업융합학회 논문집
• /
• 제15권3호
• /
• pp.71-77
• /
• 2012

This study gives the optimal reaction conditions, reaction mechanisms, reaction rates leaded from the oxidation of phenol by electron beam accelerator and ozone used for recent water treatment. It gives the new possibility of water treatment process to effectively manage industrial sewage containing toxic organic compounds and biological refractory materials. The high decomposition of phenol was observed at the low dose rate, but at this low dose rate, the reaction time was lengthened. So we must find out the optimal dose rate to promote high oxidation of reactants. The reason why the TOC value of aqueous solution wasn't decreased at the low dose was that there were a lot of low molecular organic acids as an intermediates such as formic acid or glyoxalic acid. In order to use both electron beam accelerator and biological treatment for high concentration refractory organic compounds, biological treatment is needed when low molecular organic compounds exist abundantly in sewage. In this experiment, the condition of making a lot of organic acids is from 5 kGy into 20 kGy dose. Decomposition rate of phenol by electron beam accelerator was first order reaction up to 300ppm phenol solution on the basic of TOC value and also showed first order reaction by using both air and ozone as an oxidants.