• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.415-418
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• 2008

This paper presents an innovative prototype of a new conceptual electromagnetic induction-based fluid beating appliance using voltage-fed type scries capacitor-compensated load resonant high-frequency IGBT inverter with a phase-shifted PWM and a power factor correction schemes. Its operating characteristics in steady-state are illustrated including unique features and evaluated on the basis of its computer simulation and experimental results of 10kw breadboard appliance for hot water producer and superheated steamer. The promising cost effective inverter-fed boiler appliances for electromagnetic induction-heated type fluid-heating in the pipeline systems are proposed for induction-heated boiler, super heat steamer, high temperature water producer, hot gas producer and metal catalyst heating for exhaust gas cleaning in engine, which are more suitable and acceptable for industrial, chemical, and consumer energy utilization for household and business from a practical point of view.

• Korean Journal of Human Ecology
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• v.14 no.4
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• pp.693-707
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• 2005

This study investigates the over time changes in the ownership of kitchen items, electric or non-electric, and examines the patterns of the usage and ownership of the items after categorizing them as followings: cooking appliances, kitchen appliances directly related to storing food, food processing kitchen items, and dining items. The research findings are that refrigerators and rice cookers, among the electric items, had spread to almost every households by 1990s and at the same time about thirty non-electric kitchen items had been used. Refrigerators had been used by more than 100% of the households by 2000, and on top of that, twenty or more electric kitchen items such as Kimchi fridge and freezer had been used. In the case of non-electric kitchen items, approximately 50 to 70 sorts of them are used, which indicates an increase than in 1990s. Rice cookers and gas stoves, among cooking appliances, are recognized as the essential item, and they are actually frequently-used items. As to kitchen appliances related to storing food, each household owns one of the refrigerators and Kimchi fridges, and again they are both the frequently-used. As far as food processing kitchen items are concerned, each household owns at least one or more blenders and hand blenders, six or more knives, and five or more pans. Each household owns seventeen or more rice bowls and soup bowls and twenty-four or more plates. Small plates are more frequently used than large ones.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1219-1224
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• 2006

This paper presents the friction and anti-wear characteristics of nano-oil with n mixture of a refrigerant oil and carbon nano-particles in the thrust slide-bearing of scroll compressors. Frictional loss in the thrust slide-bearing occupies a large part of total mechanical loss in scroll compressors. The characteristics of friction and anti-wear Lising nano-oil is evaluated using the thrust bearing tester for measuring friction surface temperature and the coefficient of friction at the thrust slide-bearing as a function of normal loads up to 4,000 N and orbiting speed up to 3,200 rpm. It is found that the coefficient of friction increases with decreasing orbiting speed and normal force. The friction coefficient of carbon nano-oil is 0.015, while that of pure oil is 0.023 under the conditions of refrigerant gas R-22 at the pressure of 5 bars. It is believed that carbon nano-particles can be coated on the friction surfaces and the interaction of nano-particles between surfaces can be improved the lubrication in the friction surfaces. Carbon nano-oilenhances the characteristics of the anti-wear and friction at the thrust slide-bearing of scroll compressors.

• Tribology and Lubricants
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• v.36 no.6
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• pp.332-341
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• 2020

High-speed turbomachinery implements gas foil bearings (GFBs) due to their distinctive advantages, such as high efficiency, lesser part count, and lower weight. This paper provides the test results of the static structural stiffnesses and loss factors of bump-type foil thrust bearings with increasing preload and bearing deflection. The focus of the current work is to experimentally quantify variability in structural stiffnesses and loss factors among the four test thrust bearings with identical design values and material of the bump and top foil geometries using the same (open-source) fabrication method. A simple test setup, using a rigidly mounted non-rotating shaft and thrust disk, measures the bearing bump deflections with increasing static loads on the test bearing. The inner and outer diameters of the test bearings are 41 mm and 81 mm, respectively. The loss factor, best-representing energy dissipation in the test bearings, is estimated from the area inside the local hysteresis loop of the load versus the bearing deflection curve. The measurements show that structural stiffnesses and loss factors of the test bearings significantly rely on applied preloads and bearing deflections. Local structural stiffnesses of the test bearings increase with applied preloads but decrease with bearing deflections. Changes of loss factors are less sensitive to applied preloads and bearing deflections compared to those of structural stiffnesses. Up to 35% variability in static load structural stiffnesses is found between bearings, while up to 30% variability in loss factors is found between bearings.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1019-1021
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• 1999

In this paper, we describe the design and appliance of the preventive diagnostic expert system of gas in oil for power transformer. This expert system is developed to use expert system development tool; Element Expert (NEURON DATA Inc.) Analysis is developed by four diagnose methods. In first, the standard of KEPCO is applied. It classifies the state of transformer by four level: Normal, warning, abnormal and danger. And the others are gas pattern methods, IEC code method, and Dornen & Roger Ratio method and applied later. These latter methods analyse the cause of result. Inference engine was designed with Element Expert. In last, we operate the system with sample data and we can obtain the correctly inferred result for the state of transformer.

• Journal of Mechanical Science and Technology
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• v.14 no.11
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• pp.1286-1295
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• 2000

The ventilation effectiveness is evaluated as a function of air exchange rate and supply / extract locations in a simplified model chamber using a tracer gas technique of CO$_2$ gas injected into a supply duct. Ventilation systems consist of supply and extract fans, a CO$_2$gas generator, a CO$_2$gas analyzer and a test chamber. The ventilation effectiveness is evaluated using a step-down method based on ASTM Standard E741-83. The room mean age of the model chamber is decreased with increasing air exchange rate fanged from 6to 10 air changes per hour. The ventilation effectiveness of the mechanical inlet/natural extract system is better than that of the mechanical extract system.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.128-135
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• 2013

In order to estimate the combustion characteristics and the gas interchangeability for natural gas with various compositions per each production area, equivalent gas are using to replace natural gas. It is known that an equivalent gas has the same the heating value, the compression factor, the relative density, CO emission and the burning velocity as the original natural gas. However, it is not reported that the flame shape and thermal efficiency and NOx emission by real gas appliance. In this study, equivalent gas was examined the validation to replace natural gas. The CO emission the burning velocity and the flame temperature were reconfirmed, and the flame shape, the NOx emission and the thermal efficiency were numerically and experimentally investigated. As results, there was not a large difference between natural gas and equivalent gas. This result demonstrated that there was no problem using equivalent gas to replace natural gas.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.3
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• pp.137-142
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• 2013

A small air-conditioner or chiller for a constant temperature bath normally uses a constant speed compressor. The constant speed compressor is relatively inexpensive, but it uses on/off control for capacity modulation. The on/off control has several disadvantages, specifically energy loss and large temperature fluctuation. Continuous operation with a bypass system can be an alternative to on/off control, for capacity modulation. In this study, a heat pump system having a hot-gas bypass and a liquid bypass was adopted. The performance of the bypass-type heat pump was measured, by varying the bypass valve opening. The differences of the COP between the hot-gas bypass and the liquid bypass, in the cooling and heating operations, were within 2% and 1%, respectively. The liquid bypass showed a wider range of capacity control in the cooling operation but the hot-gas bypass showed a wider range of capacity control in the heating operation.

• Journal of the Korean Institute of Gas
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• v.4 no.2 s.10
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• pp.46-51
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• 2000

It is required that fuel gas accidents should be managed carefully along with the increase of fuel gas consumption. Factors to cause accidents were investigated through a systematic analysis of gas accidents during recent 4 years, which could be applied to prepare countermeasures to reduce gas accidents. The thawing season is found to be weak to gas accidents, showing a slightly higher rate of accident occurring than average. During this term although the number of LPG accident is similar to that of yearly average, countermeasures are required for LPG facilities since the portion of accident is large; in detail, user's carelessness, defective facility, or instrument failure are major causes. The number of city gas accident facility is larger than that of yearly average; particularly, defective facilities, third-party work, and appliance failure are major causes. As a result, countermeasures have been suggested for the accident of large portion or above yearly average.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.1-5
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• 2017

Leaking of natural gas, which is mostly methane, in a confined living space creates flammable atmosphere and gives rise to explosion accident. The minimum amount of leaked methane for explosion is highly dependent on the degree of mixing in the confined space. This paper proposes a method for estimating minimum amount of flammable gas for explosion by using Gaussian distribution explosion model(GDEM) and experimental explosion data. The explosion pressure in the confined space can be estimated by assuming the Gaussian distribution of flammable gas along the height of an enclosure and estimating the maximum amount of gas within flammable limits, combustion of the estimated gas with constant volume and adiabatic or isothermal mixing in the confined space. The predicted minimum gas amount for an explosion is tied to explosion pressure that results in a given building damage level. The result shows that very small amount of methane leaking in the confined space may results in a serious gas explosion accident. This result could be applied not only to setting the leak criteria for developing a gas safety appliance but also to accident investigating of explosion.