• Journal of Korean Society of Environmental Engineers
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• v.35 no.5
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• pp.350-355
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• 2013

Little information is available for emission pathway even if HFC-134a that is known as one of the major greenhouse gases has been broadly used in Korea. This paper attempts to clarify the emission characteristics of HFC-134a used for refrigerant of cold drinking vending machines (CDVMs) at the use- and disposal-phase. We measured the residual amounts in the scrap CDVMs of 47 by applying commercial recover for refrigerant. The first-order kinetic model was introduced and the emission rate would be proportional to the remaining quantity of refrigerant. The emission factor at the use-phase was determined indirectly to be $6.9{\pm}0.7$ %/yr within a confidence interval of 95%, using information on residual amount and elapsed operation time at the disposal point. Correspondingly, the annual emission rate of HFC-134a per CDVM was determined to be 11.6 g. The average residual rate of HFC-134a in scrap CDVMs was assessed to be $62.5{\pm}2.2%$, leading to a potential emission amount of 144.8 g per scrap CDVM. The chemical compositions of refrigerants from scrap passenger vehicles are quite similar to those of new refrigerants, suggesting that the refrigerants from scrap passenger vehicles could be reused. During the recovering process of refrigerant, the recovered refrigerant was contaminated by compressor lubricant that accounted for about 30% in weight. It is necessary to separate the refrigerant from the recovered material contaminated by lubricant for recycling and reuse the refrigerant.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.4
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• pp.428-435
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• 2015

This paper presents the experimental study of cabin thermal comfort using a cold storage heat exchanger in a vehicle air-conditioning system. Recent vehicle-applied ISG functions for fuel economy and emission, but when vehicles stop, compressors in the air-conditioning system stop, and the cabin temperature sharply increases, making passengers feel thermal discomfort. This study conducts thermal comfort evaluation in the vehicle, which is applied to a cold storage system for the climate control wind tunnel test and the vehicle fleet road test with various airflow volume rates and ambient temperatures blowing to the cold storage heat exchanger. The experimental results, in the cold storage system, air discharge temperature is $3.1-4.2^{\circ}C$ lower than current air-conditioning system when the compressor stops and provides cold air for at least 38 extra seconds. In addition, the blowing airflow volume to the cold storage heat exchanger with various ambient temperature was examined for the control logic of the cold storage system, and in the results, the airflow volume rate is dominant over the outside temperature. For this study, a cold storage system is economically useful to keep the cabin at a thermally comfortable level during the short period when the engine stops in ISG vehicles.

• Journal of ILASS-Korea
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• v.22 no.4
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• pp.185-189
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• 2017

In Korea, sales of passenger cars using diesel and LPG fuels were continuously increased in recent years. From now on 2030, the registrated vehicles will close in about twenty five million in Korea. From these reason, Investigation on the comparison of exhaust emission characteristics of passenger cars using LPG and Diesel fuel in variation of driving mode and ambient conditions were conducted in this study. Exhaust emission characteristics of test vehicles were measured and analyzed by using chassis dynamometer and emission analyzer. Also, test vehicles were selected on the diesel vehicle with 1.7L engine and LPG vehicle with 2.0L engine. In order to study on emission characteristics according to driving cycles, CVS-75, NEDC, US06, SC03, Cold-FTP and HWFET were applied and the test conditions were set up the cases of A/C on and hot start. From these results, it is revealed that the NOx emission of diesel vehicle was higher than that of LPG vehicle and the case of CO emission shows the opposite patterns. In the HC emission, the emission increasing patterns not showed but the NOx emission of diesel vehicle and CO emission of LPG vehicle were showed the variation patterns according to the various driving modes.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.8
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• pp.409-413
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• 2001

In the electron-gun of CRT, the Mo-tip FEA was employed as cold cathode in order to replace the conventional thermal cathode. The Mo-tip FEA was designed and fabricated according to CRT specification and mounted on the electron-gun. It was known that fabricated cold cathode electron-gun showed better performance in terms of maximum emission current and switch-on time when compared with the ones of thermal cathode electron-gun, but some geometrical structures in the inside of electron-gun must be changed to reduce the gate leakage current. Finally, the potential applicability was guaranteed by means of operating the 19 inch-sized LG-color CRT using the fabricated cold cathode electron-gun.

• Journal of the Semiconductor & Display Technology
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• v.11 no.1
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• pp.61-65
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• 2012

In this study, for use of carbon nanotubes (CNTs) as a cold cathode of x-ray tubes, we examine the effects of selective growth of CNTs on their field emission properties and long-term stability. The selective growth of CNTs was performed by selectively etching the catalyst layer which was used for CNTs' nucleation. CNTs were grown on conical-type tungsten substrates using an inductively-coupled plasma chemical vapor deposition system. For all the grown CNTs, their morphologies and microstructures were analyzed by field-emission scanning electron microscope and Raman spectroscopy. The electron-emission properties of CNTs and the long-term stability of emission currents were measured and characterized according to the CNTs' growth position on the substrate.

• Journal of Information Display
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• v.2 no.3
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• pp.44-47
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• 2001

The extracted field emission current can be used to controllably heat microfabricated cold field emission cathode tips. The heating can be sufficient to smooth and recrystallize the tip surface by surface self-diffusion, and at least partially clean the surface of contaminants by thermal desorption. Self-heating not only allows for the achievement and maintenance of stable emission characteristics, but can be used to make the current-voltage characteristics of microfabricated field emitter tips nearly identical to one another. The resulting improvement in emission uniformity will allow for more reliable array operation at increased electron emission current densities.

• Journal of the Korean Institute of Gas
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• v.18 no.6
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• pp.7-13
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• 2014

As the interest on the air pollution is gradually rising up at home and abroad, automotive and fuel researchers have been working on the exhaust emission reduction from vehicles through a lot of approaches, which consist of new engine design, innovative after-treatment systems, using clean (eco-friendly alternative) fuels and fuel quality improvement. This research has brought forward various main issues : whether PM emissions should be regulated for diesel and gasoline vehicles and whether gasoline and LPG powered vehicles can be further neglected from PM emission inventories. Finally, the greenhouse gas ($CO_2$, $CH_4$, $N_2O$) regulation has been discussed including automotive emission regulation. The greenhouse gas and emissions (PM) particle of automotive had many problem that cause of ambient pollution, health effects. This paper discussed the influence of LPG fuel on automotive cold startability and exhaust emissions gas. Also, this paper assessed emission characteristics due to the test temperature. These test temperature were performed by dividing the temperature of the test mode and the lowest local temperature in winter. Through this study, the correlation of cold startability, exhaust emission and greenhouse gas emission was analyzed.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.87-100
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• 2000

HC and CO emissions during the cold start contribute the majority of the total emissions in the legislated driving cycles. Therefore, in order to minimize the cold-start emissions, the fast light-off techniques have been developed and presented in the literature. One of the most encouraging strategies for reducing start-up emissions is to place the light-off catalyst, in addition to the main under-body catalyst, near the engine exhaust manifold. This study numerically consider three-dimensional, unsteady compressible reacting flow in the light-off and under body catalyst to examine the impact of a light-off catalyst on thermal response of the under body catalyst and tail pipe emission. The effect of flow distribution on the temperature distribution and emission performance have also been examined. The present results show that flow distribution has a great influence on the temperature distribution in the monolith at the early stage of warm-up process and the ultimate conversion efficiency of light-off catalyst is severly deteriorated when the space velocity is above $100,000hr^{-1}$.

• Journal of Mechanical Science and Technology
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• v.14 no.6
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• pp.699-703
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• 2000

Experiments were carried out to investigate the characteristics of the hydrocarbon (HC) emissions and to reduce cold start hydrocarbons in gasoline engines. An HC adsorber was, used and it coated was by Pd/Rh catalyst with zeolite on a honeycomb monolith. The HCs were efficiently trapped at temperatures below $100^{\circ}C by physical adsorption. After adsorption, they were reduced gradually by the catalytic oxidation of Pd/Rh catalysts as the adsorber temperature increased above $100^{\circ}C. Increasing amounts of methane, ethylene and n-butane were emitted as the fuel-air mixture became richer and the engine speed decreased. As the temperature of adsorber increased, high-number carbons into low-number carbons. Thus, the C4 concentration decreased significantly during the first 30 seconds, and the C2 concentration increased continuously.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.103-111
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• 2001

During cold-start period, the reduction of exhaust emissions is a challenging task. To decrease harmful gaseous substances such as HC, it is necessary to realize a fast catalyst warm-up. In this study, the performance of dual pipe exhaust system have been carried out through different test mode. From measurement of gas temperature and HC concentration, the following conclusions were derived ; 1) Compared with single pipe, dual pipe exhaust system remarkably increase temperature of exhaust gas going through M.C.C(Main Catalytic Converter). 2) W.C.C.(Warm-up Catalytic Converter) also decreases HC emission. To reduce HC emission, it is helpful to use W.C.C. as well as dual pipe exhaust system. 3) Using finite element method, it is shown that inner parts have much higher distribution of temperature than outer parts.