• Journal of Environmental Science International
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• v.16 no.4
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• pp.415-423
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• 2007

This study assessed the characteristic of BTEX (Benzene, Toluene, Ethylbenzene, Xylene) concentration ratios of industrial emission sources and the neighborhoods of industrial area, fuel such as gasoline, light oil, LPG, and similar gasoline, and ambient air in Daegu. The BTEX in aromatic compounds was the most abundant VOC in Daegu. The BTEX ratios were (0.2:2.6:1.0:1.8) for the neighborhoods of industrial area, (2.6:11.3:1.0:1.2) for residential area, (2.2:11.0:1.0:1.6) for commercial area, (1.0:14.9:1.0:1.3) for industrial area, and (0.2:2.6:1.0:1.8) for the neighborhoods of industrial area. Average BTEX ratios in Daegu were B/T ratio (0.1), B/EB ratio (1.5), B/X ratio (1.1), T/EB ratio (12.6), T/X ratio (10), EB/X ratio (0.7), Expecially, B/T ratio in Daegu was similar as the other cities, Bangkok, Manila, and Hongkong. Comparing other cities with B/T ratio, the main sources of VOC were vehicular exhaust and emission of industrial facilities. Furthermore, BTEX correlation were evaluated at the emission sources and regional areas. Results showed that correlation coefficient values of emission sources, fuels and neighborhood of industry were significant magnitude above 0.65(p<0.01). Also, there showed highly significant correlations among BTEX. Calculated correlation coefficients of ambient air sampling sites were $0.61{\sim}0.954$ for commercial /residential area and $0.613{\sim}0.998$ for industrial area. However, they showed different correlation between commercial/residental area and industrial area. It implied that the emission sources were different from each area.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.2
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• pp.111-116
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• 2000

Transboundary air pollution has recently become an area of increasing scientific interest and political concern as countries are receiving air pollutants from their neighbors. In order to gain a better understanding of the long-range transport processes of air pollutants and the source-receptor relationships among neighboring countries, an atmospheric transport model coupled with a RAMS(Regional Atmospheric Modeling System) model was applied to the East Asia region during the entire month of January 1993. The scalar transport option of the RAMS model was used to calculate special atmospheric constituents such as trace gases or aerosols. The sulfate production in clouds and rainwater and its removal processes by dry and wet deposition were considered. The sulfate budget from source regions to receptor regions was estimated by analysing the source-receptor relationships. When a specific receptor site revealed a sulfate value higher than the sulfate concentration based on its own source origin, this was taken to indicate long-range transport from another source region. The contribution ratio from various source region was calculated. The contribution ratio of dry and wet deposition was higher on the main continent of the East region. Furthermore, the high deposition amounts were identified on the west coast of Korea and the East China Sea.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.3
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• pp.218-224
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• 2006

The performance of an air to water vapor compression heat pump has been investigated experimentally. The main purpose of this study was to study the possibilities of using hydrocarbon refrigerants as a working fluid to replace R-22 for vapor compression heat pumps. Pure R-22 and R-290, R-600a, R-1270 were considered as working fluids. The performance of the system was characterized by compression shaft work, refrigeration capacity, pressure ratio, discharge temperature and COP. The experimental apparatus has basic parts of cycle that uses the air as a heat source. The experimental results show that refrigeration capacity of HC refrigerants is same or higher than that of R-22. On the other hand, compression shaft work of HC refrigerants is lower than that of R-22. Compression shaft work is lower than that of R-22. Come to the conclusion that, it is possible that hydrocarbon refrigerants could be drop-in alternatives for R-22.

• Journal of the Korean Solar Energy Society
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• v.39 no.6
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• pp.83-91
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• 2019

Photovoltaic thermal (PVT) collectors are devices that simultaneously produce electricity and heat. Research on conventional air-type PVT collector focuses on installing baffles to enhance the collector's thermal performance. However, the baffles have pressure drop inside the collector which degrades the thermal performance. Thus, it is necessary to design baffles to smoothen the flow inside the air-type PVT collector. Alternatively, installing perforated baffles in air-type PVT collectors can reduce the collector weight, but parameters such as the diameter of the perforated holes and the height of the perforated plates should be considered. Therefore, the main aim of this study was to analyze thermal characteristics of each variable of perforated baffles installed inside air-type PVT collector. For this purpose, the uniformity of air flow in the collector was compared through NX program, and the resultant heat gain and thermal efficiency of the air-type PVT collector were compared and analyzed. Therefore, the main aim of this study was to analyze thermal characteristics of each variable (Baffle angle, length, height, pitch, perforated ratio) of perforated baffles installed inside air-type PVT collector. For this purpose, the uniformity of air flow in the collector was compared through CFD program, and the resultant heat gain and thermal efficiency of the air-type PVT collector were compared and analyzed. As a result, the maximum outlet temperature was increased by 1.45 times and the heat gain was increased by 193.8 Wth, depending on the perforated baffle plate, compared to the collector without the baffle. The heat transfer performance showed that the maximum internal velocity was 1.61 times higher and the Reynolds number was 1.06 times higher depending on the parameters of the baffle plate.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.2
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• pp.149-153
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• 2003

Besides the fuel spray behavior and combustion chamber shape. an air motion has a key role on exhaust gas emission and performance in a DI diesel engine. A swirl ratio represents the ratio of the intake swirl velocity to the engine speed. The main purpose in this work is to investigate the effects of the swirl ratio to the combustion characteristics. A shroud valve machined to change the swirl ratio. Test was carry out by changing the engine speed, nozzle diameter and swirl ratio in a single cylinder diesel engine. From this study, the optimized combustion was found at swirl ratio 2.7. And it was also found that the increasing the maximum cylinder pressure with an increasing swirl ratio lead to decrease a smoke and to increase NOx.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.362-367
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• 2003

It is shown that the effect of variable parameters on flame structures and NOx emissions in the laminar partially premixed methane-air flames with a co-axial Bunsen burner. Objectives of this paper is to understand the effects of flow variables on NOx emissions and the flame structure with OH chemiluminescence, including reconstructed image by abel inversion processing at each conditions. A fuel flowrate of 200 [cc/min] was fixed and the amount of air was varied from 400 to 1200 [cc/min]. The experimental variables were equivalence ratio(${\Phi}$ fuel split percentage(${\sigma}$ and inner tube recess(x/D). Flow conditions were ranged from $1.36{\sim}4.76$(equivalence ratio), $50{\sim}100$(fuel split percentage) and $0{\sim}20$(inner tube recess). NOx analyzer and ICCD camera with a OH filter were used as a main experimental apparatus. In addition, Abel inversion, which is a kind of tomography and valuable to estimate a two-dimensional structure of co-axial flames from cubical information, was employed for combustion diagnostics. Results from this study indicate that the main effects depend on equivalence ratio and next sigma, x/D for NOx production and OH formation. Throughout Abel inversion, we could affirm the maximum position and the tendency of OH radical intensity by variants at five axial heights above the burner exit.

• Journal of ILASS-Korea
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• v.6 no.1
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• pp.25-34
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• 2001

Several efforts to meet the exhaust gas regulation have been undertaken by many researchers in recent years. Main researches are on development of design techniques of intake port and combustion chamber, atomisation of fuel and precise control of air-fuel ratio, post-treatment of exhaust gas and so on. Engine technology is changed from PFI to GDI to correspond with exhaust gas regulation. GDI technique makes it possible to preserve lean air-fuel ratio and control accurate air-fuel ratio. Nevertheless, It is not cleared that information of spray characteristics and atomization process are very dependent on fluctuation of pressure and change of temperature in intake stroke. In this study, a constant volume combustion chamber is manufactured to investigate various fluctuations of in-cylinder pressure for injection duration. It is taken photographs of injection process of conventional GDI injector using PMAS. Then, it was verified experimently that ambient conditions as temperature and pressure of combustion chamber have effects on process of spray growth and atomization of fuel.

• Journal of the Korea Institute of Building Construction
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• v.6 no.3 s.21
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• pp.107-114
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• 2006

In this study, the experiment was carried out to investigate and analyze the engineering properties of concrete using fine aggregate of PS bal slagl. The main experimental variables were water/cement ratio 30, 40, 50(%), water content $170kg/m^3$, replacement ratio of slag fine aggregate 0, 25, 50, 75(%) in experiment I and water/cement ratio 30, 40, 50(%), water content 165, 170, 175($kg/m^3$), replacement ratio of fine aggregate of PS ball 0, 50 in experiment II. According to the test results, the principle conclusions are summarized as follows (1) The workability of slag fine aggregate-mixed concrete tends to improve, as the replacement rate increases. (2) The air content of slag fine aggregate-mixed concrete tends to decrease, as the replacement rate increases. (3) The unit volume weight of slag fine aggregate-mixed concrete tends to significantly increase, as the replacement rate increases. (4) The compressive strength of slag fine aggregate-mixed concrete tends to show more increasing propensity, in case the curing period is relatively long, as the replacement rate increases.

• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.128-133
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• 2001

It is generally known that the concrete structure subjected to severe environment is much affected by the corrosion of reinforcement, the freezing and thawing action of concrete structure. The main objective of this study is to investigate the freezing and thawing resistance of concrete including fly ash. The effect of the air content in concrete using fly ash is investigated. The experimental study is conducted for 10 mix-ratio cases of concrete of which variables are content of fly ash, concrete compressive strength and containment of air-entrained admixtures. Test results show that the freezing and thawing resistance improves as the amounts of fly ash increase, and concrete with air-entrained admixtures has good freezing and thawing resistance. The concrete with fly ash is to be included air-entrained admixture according to content of fly ash in order to increase the freezing and thawing resistance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.215-217
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• 2008

This paper deals with the structural vibration characteristics for an outdoor units support of an air-conditioner. Even though main noise sources are compressor noise and fluid noise which is caused by the fan, the structural modification of the outdoor units support may affect vibration and noise. In this paper, damping ratios for two kinds of an outdoor units support of an air-conditioner are measured through the modal testing. In order to reduce the structural borne noise due to an outdoor units support of an air-conditioner, four kinds of rubber materials are selected and tested.