• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1225-1231
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• 2006

Recently, as the climate of temperature change has happened worldwide, To solve this problem, Kyoto protocol was taken to regulate global warming on Feb. 2005 and each country is making efforts to prevent global warming. In the automotive industry, R-134a refrigerant is widely used most these days because it has zero ODP(Ozone Depletion Potential). But R-134a GWP(Global Warming Potential) is so high. Therefore, replacement refrigerant desperately is needed as a alternative refrigerant. So, R-l52a is considered as one of the alternative refrigerants due to zero ODP and lower GWP against as required on Europe Committee. In this paper, performance of the air conditioning system between R-134a and R-152a is investigated experimentally. In the bench level, cooling capacity, condensing capacity, COP of automotive air conditioning system are ovaluated by means of air velocity entering the condenser and compressor revolution speed with optimized charge refrigerant quantity. Result of this study, R-152a refrigerant shows the possibility as alternative refrigerant of current R-134a in automotive air conditioning system.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.17-23
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyze the heat quantity of homogeneous charge methane-air mixture under various initial pressures, excess air ratios and ignition times. As the overall pressure increase, the values of maximum combustion pressure, maximum heat release rate and cumulative heat release have been increased. But it is not very meaningful to compare with some values such as maximum combustion pressure, maximum heat release rate and cumulative heat release for different overall pressure due to the different heat energy of supplied fuel. So the each value is needed to be compared with normalized value, which is divided by the entered fuel energy. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. As the overall pressure increase, the CHR ratios and the UHC ratios have been decreased, while the HL ratios have been increased. The CHR ratio of 300 ms has the higher value than that of 10000ms, and the HL ratios of 300 ms have a lower value.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.9-14
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• 2006

This study presented the feasibility of R152a refrigerant as an alternative of R134a which is used in the current automobile air conditioning system. The performance of air conditioning system installed in the actual vehicle was tested using the climate wind tunnel. The experiments were conducted at various refrigerant charge quantities and various driving conditions such as city traffic, highway traffic and parking. Same components and lubricant were used for both R134a and R152a system. The effects of air set values of thermal expansion valve on the performance were also investigated. In case of the R152a system, refrigerant charge quantity can be reduced about 20%, better performance and superior compressor durability is expected due to the lower discharge pressure compared to the R134a system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.3
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• pp.175-180
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• 2008

Flow quantity to supply to a coil in floor heating system is important to achieve comfortable indoor air condition in the winter season. The hot water header is used to distribute the water into the coil. Experimental study has been performed using the water header that have 5 branches consisted of flow control valves and automatic shut-off valves. Each branch line connected it with X-L pipe. Experimental tests accomplished it to investigate the flow distribution characteristics of the hot water header. Experimental results show that the selection of the pump head and differential pressure are very important to save running energy of the system, and high differential pressure needs more friction loss in the case of suitable differential pressure for balancing of the header.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2508-2510
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• 2001

Frequency of cavity vibration in air flowing tube is closely related to a velocity of air. In this research, an instrumentation system to estimate frequency of cavity vibration for measurement of the velocity and quantity of a moving fluid is implemented by using DSP TMS320C32. Measurement of the generated sound wave frequency in cavity is difficult because of environmental noise. Adaptive filters are used to eliminate this noise effectively. The estimated velocity and quantity of a moving fluid by proposed system is compared with the results measured by a standard flow meter.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.57-63
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• 2000

This paper deals with a study on combustion and emission characteristics of a direct injection diesel engine dual fueled with natural gas. Dual fuelling systems tend to emit high unburned fuel especially at low load, resulting in a decreased thermal efficiency. This is because natural gas-air mixtures are too lean for flame to propagate under low load conditions. Suction air quantity and injection timing controls are very useful to improve emissions and thermal efficiency at low load.

• KIEAE Journal
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• v.10 no.1
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• pp.19-24
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• 2010

Modern people are spending most of time in interior area. Indoor air environmental problem is one of the most effective factors influenceable to human health. Furthermore, saving energy and making ventilation system for pleasant indoor environment are necessary when it is faced shortage of energy over the world. In our country's case, it is already imposed that required quantity of air ventilation in buildings is 0.7 times per hour on "The regulation on building engineering system". As on the rise of the interests about Indoor air environment, Heat and Carbon dioxide emissions from User's metabolism, activity, furniture, and construction materials etc. could be the causes of Indoor air pollution. If these materials stays in Indoor air for so long, it could directly influence the user's health condition with a disease. As of building's sterilization improved that raised more mechanical ventilation. It also leads much energy waste in a period of high price of fossil fuel. Therefore, the way that saves energy and effective control of indoor ventilation is urgently needed. So, this study places the purpose on validating volume of indoor ventilation and user's comfortable degree by comparison CO2 emission rate through changing floor temperature.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.6
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• pp.89-96
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• 2001

This paper presents a decision making technique of reasonable $O_2$quantity needed to resolve organic matter via microbe in wastewater treatment. Decision making system of inferring reasonable $O_2$quantity consists of three parts. The first part is to compute reasonable $O_2$quantity with given process data. The second part is to find output features of processed wastewater using process model when $O_2$quantity is changed to a value inferred from decision making system. The third part is to show the results of decision making system. In order to verify performance of proposed decision making system computer simulation was done with process data gathered during 40 days. Simulation result shows that $O_2$quantity can be reduced over 10% under the condition of satisfying the specifications for processed wastewater.

• Proceedings of the SAREK Conference
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• 2006.11a
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• pp.106-106
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• 2006

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.3
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• pp.45-52
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• 1987

Generally the factors affected largely by the cold cracking sensitivity of the weld are the quantity of the diffusible hydrogen, the brittleness and hardness of the bond area and the tensile restraint stress. These factors have relation each other, and if we can reduce one of these factors, it becomes instrumental to the root cracks prevention of weld. This study deals with the gravity type-underwater-welding of KR Grade A-3 marine steel plate using E4303 welding electrode in order to compare wet-underwater-welding with in-air- welding, resulting in obtaining the tensile restraint characteristics, the hardness distribution, the quantity of diffusible hydrogen and the macro- and micro-crack properties in both underwater and in-air welds. The main results obtained are as follows: 1) The quantity of diffusible hydrogen measured for 48 hours is about 18cc/100g-weld-metal for the in-air-weld of one pass and about 48cc/100g-weld-metal for the underwater-weld of one pass which is about 3 times penetration of diffusible hydrogen compairing with the case of the in-air-weld. However, it was experimentally confirmed that, by the multi-pass welding of 2 to 5 passes, the diffusible hydrogen in the underwater weld metal can be reduced as much as 27 to 49%. 2) The hardness of the weld metal indicates the highest value in the heat affected zones of underwater weld for more rapid cooling rate, resulting in the higher sensitivity of cold cracking. So, it is desirable to soften the higher hardness in the HAZ by tempering effect such as the multi-pass welding in the underwater welding. 3) At the bond vicinity of the underwater weld HAZ, micro cracks were found as resulted by both more rapid cooling rate and more diffusible hydrogen and also by the stress corrosion cracking under the tensile restraint stress in the underwater. But this could be prevented by the tempering effect of the following weld bead such as the multi-pass welding.