• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2446-2448
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• 2001

In addition to the stabilization of electricity supply and the quality management of electricity, load balance has been an important strategy for achieving high quality load management. Among many techniques for load management, direct load management has been actively studied and applied for increasing the efficiency of power facility and suppressing peak load. In Korea, the highest peak load is demanded in summer rather than in winter, and almost 50% of the peak load comes from cooling load. Currently, applicable systems are limited to air conditioners that have the cooling capacity less than 2kW. This paper describes the development of remote controlled air conditioners and the result of the field test of the new type air conditioner. The technical specification based on the test will be applied to the new model of the remote controlled air conditioner. The wide distribution of the air conditioners to the public will be helpful to control peak demand due to cooling load in summer time. Financial investment to generating, transmission, distribution facilities will be decreased from flatting the seasonal power load.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.5
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• pp.403-410
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• 2007

In this study, natural refrigerants and their mixtures that can supplement and replace R12 and R134a in automobile air-conditioners are studied. R134a is currently used as the refrigerant in new motor vehicle air conditioners, replacing the ozone depleting refrigerant R12. Although R134a has no ozone depletion potential, it has a relatively large global warming potential, approximately 1300 times that of $CO_2$ over a 100 year time horizon. For this reason, performance of natural refrigerants and their mixtures containing R152a, RE170 (Dimethylether, DME) and R600a (Isobutane) are measured under 2 different temperature conditions. They were tested in a refrigerating bench tester with an open type compressor. The test bench provided about 4 kW capacity and water and water/glycol mixture were employed as the secondary heat transfer fluids. Test results show that the coefficient of performance (COP) of these refrigerants is up to 21.55% higher than that of R12 in all temperature conditions. Overall, these fluids provide good performance with reasonable energy savings without any environmental problem and thus can be used as long term alternatives for automobile air-conditioners.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.100-108
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• 2009

Due to rapid economic growth, the usage of residential cooling electrical appliances such as air conditioners and refrigerators has increased dramatically for the last decades. In other to reduce its energy consumption, the authorities have applied energy efficiency standards for principal appliances, including air conditioners. and then it can anticipate environmental effects. In this paper, it presents the actual procedure to analyze the effects for the decline in the $CO_2$ emissions and its methodology for the efficiency improvement of the air conditioner that takes a great portion of the summer power uses.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.91-100
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• 2004

Energy efficiency evaluation method for a multi-type air conditioning system still has not been developed. In this study, analysis on capacity range and evaluating method of standards for air conditioners was conducted with world-wide Standards. It is not a proper approach to use the standards for residential air conditioner to multi type air conditioners. Some difficulties and problems are commented in this study with overview of the standards. Through the analytic research, an evaluating method for multi type air conditioner was suggested with Integrated Part Load Value (IPLV). The suggested concept for evaluating energy efficiency during part load condition considers building load pattern and operating hours of the system at different locations. Load was weighted in IPLV to consider not only the concept of occurrence of outdoor temperature such as bin method but also operation hours of the system. An experiment about the IPLV was conducted with variable air volume ducted type air conditioning system and multi-type system through modified code tester to give a glance at quantitative value of the IPLV.

• The Journal of the Korean dental association
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• v.17 no.9 s.124
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• pp.695-700
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• 1979

An experimental study was performed to study the tissue reactions to tissue conditioners in rabbits. Thirty rabbits were divided into three groups, 10, Hydro-cast group, 10, Coe-comfort group, and 10, heat-cured resin group. Tissue conditioners and heat-cured resin were embedded in the oral mucosa of rabbits. The tissue specimens were removed on 3rd, 7th, 14h, 21st and 28th day after embedding and examined under microscope after staining them with H-E stain, Van Gieson's stain, Masson's trichrome stain and PAS reaction. The results were as follows : 1. Tissue reactions to tissue conditioners were somewhat different from each other in the early stage, but, with the increase of the embedding period, the fibrous capsule was thickened in both. These tissue reactions were similar to those to heat-cured resin. 2. Newly formd fibrous components were stained deep-red with Van Gieson's stain and dark-green with Masson's trichrome stain. But their stainability was decreased as collagenous fibers became matured. 3. Newly formed fibrous components showed intense PAS reactivity, but PAS reactivity was reduced as the connective tissue capsule became completed.

• Journal of the Korean Society of Tobacco Science
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• v.5 no.1
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• pp.87-95
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• 1983

This study was conducted to evaluate the affect of soil conditioners and their application rates on the growth, Yield and quality of Flue-cured tobacco. Soil conditioners for this study were Montmorillonite arid Zeolite as clay mineral source and Rice hull and Sawdust as organic source. Their application rates were 500, 1000, 2000kg/10a. The growth of tobacco plants was promoted, compared with that of Non- treated plot (control) by Zeolite, Montmorillonite and Rice hull application but decreased by Sawdust application. During tobacco growing season soil moisture content, compared with control, was increased by Zeolite and Montmorillonite application but decreased by Rice hull and Sawdust application. In contrast to soil moisture content, soil temperature was higher in the Rice hull and Sawdust plot than in the plot of Zeolite and Montmorillonite. The treatment of Sawdust, compared with control, obviously accelerated the maturity of tobacco, increased reducing Sugar but decreased total alkaloids, nicotine and nitrogen content of cured leaves. The Sawdust Plot decreased the Yield (kg/10a) with significant difference by 1 %level but significantly increased leaf quality (Won/kg) and value (Won/10a) by 1%and 5 %level, respectively. The present application , ate of Nitrogen in Korea (12.5kg/10a) seems to be excessive for Flue-cured tobacco production.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.984-991
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• 2006

The applications of multi air-conditioners into multiplex and high-rise buildings have been increased by replacing central air-conditioning systems. The pipe length and altitude difference between the indoor and outdoor units can be increased based on installation conditions, which may increase the possibility of flash gas generation at the expansion device inlet. The flash gas generation causes rapid reduction of refrigerant flow rate passing through the expansion device, yielding lower system efficiency. Accumulator heat exchangers have been widely used in multi air-conditioners in order to minimize flash gas generation and obtain system reliability. However, the studies on the heat transfer characteristics and pressure drops of accumulator heat exchangers are very limited in open literature. In this study, the heat transfer rates and pressure drops of accumulator heat exchangers were measured with refrigerant flow rate and operating conditions by using R-22. The heat transfer rate increased with the increase of refrigerant flow rate, while subcooling decreased. The heat transfer rate enhanced with the reduction of inlet superheat and subcooling due to the increased temperature difference between the accumulator and inner heat exchanger.

• Journal of Power Electronics
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• v.16 no.3
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• pp.970-981
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• 2016

Leakage currents occur in pulse-width-modulated voltage source inverter (PWM-VSI)-fed permanent magnet synchronous motor (PMSM) drives for air-conditioners, which seriously affect system safety and operation performance. High accuracy modeling and prediction of leakage currents are key issues for the design and implementation of air-conditioning products. In this study, the generation mechanism of leakage currents is discussed. A systematic modeling approach of leakage currents is proposed, including the modeling of leakage current sources and leakage current paths. By using the proposed approach, the complete model of leakage currents in PWM-VSI-fed PMSM drives for air-conditioners has been developed based on the extraction of all parameters. A comparison between the simulated leakage currents based on the developed model and measured leakage currents in the outdoor unit of an air-conditioning product is conducted. The comparison verifies the effectiveness of the proposed modeling approach, and the developed model exhibits high accuracy within a wide frequency range.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.292-302
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• 1998

In this study, 14 refrigerant mixtures composed of R32, R125, R134a, R143a, R152a, and R1270(Propylene) were tested in a breadboard heat pump in an attempt to replace R22 used in most of the residential air conditioners and heat pumps. The heat pump was of 1 ton capacity and water was employed as the secondary heat transfer fluids. All tests were conducted under ARI test A condition. Ternary mixtures composed of R32, R125, and R134a were shown to have 4∼5% higher COP and capacity than R22 and hence they seem to be very promising candidates to replace R22. On the other hand, ternary mixtures containing R125, R134a, and R152a have lower COP and capacity than R22. R32/R134a binary mixtures show a 7% increase in COP and have the similar capacity to that of R22 and hence they are also good candidates to replace R22. Special care must be exercised when a suction line heat exchanger is used with these mixtures in air conditioners. Finally, the compressor discharge temperatures of all mixtures tested were lower than those of R22 by 15.g∼34.7t, which indicates that these mixtures would offer better system reliability and longer life time than R22.

• Journal of Power System Engineering
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• v.3 no.2
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• pp.5-12
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• 1999