• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.377-385
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• 2005

An analytical model was developed using the lumped mass parameter method to estimate temperature distribution of metal parts and refrigerant of the hermetic reciprocating compressor, All of the lumped mass has been equated with the first law of thermodynamics. In the delivered equation, correlations of heat transfer coefficient in the heat transfer equation were taken from open literature. The equations are solved by Gauss-Jordan method simultaneously. To verify the developed numerical program, an experiment was conducted with a domestic refrigerator. The compressor which had been installed at the bottom of the experimental refrigerator was modified to measure internal temperature. Model verification test was conducted at $30^{\circ}C$ outdoor temperature with variation of compressor cooling conditions. As a result, there is a good consistency between calculated temperature and measured one.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.27-35
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• 1998

An experimental study was performed to investigate the optimum cycle of an inverter heat pump as a function of frequency. The performance of the inverter heat pump with the rated cooling capacity of 4,141 W(3,550kcal/h) was measured with a variation of frequency, indoor and outdoor temperature, and length of capillary tube in the psychrometric test room. As a base case, the inverter heat pump with the standard capillary length of l,000mm(optimum size for the frequency of 60Hz) and ASHRAE Test condition "A" was tested by varying frequency from 30Hz to 80Hz. Then, the optimum cycles were investigated by varying the length of capillary tube at each frequency level of 30, 60 and 80Hz. Based on the experimental data, the change of system characteristics between the optimum and the base case were analyzed for each selected frequency level. Generally, for low frequency level(30Hz), the longer length of the capillary tube compared with the standard size showed the higher energy efficiency ratio(EER), while for high frequency level(80Hz) the shorter length of the capillary tube showed the higher EER.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.398-403
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• 2005

The cooling performance of a transcritical $CO_2$ cycle varies significantly with a variation of refrigerant charge amount. In this study, the performance of the $CO_2$ system was measured and analyzed by varying refrigerant charge amount with a change of cycle option. The applied cycle options are the single-stage compression system, two-stage compression with 1-EEV system, and two-stage compression with 2- EEV system. The optimum normalized charge were 0.363, 0.297, and 0.282 for the two-stage compression with 2-EEV system, two-stage compression with 1-EEV system, and single-stage compression system, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.2
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• pp.49-54
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• 2016

The purpose of this study is to analyze the indoor temperature distribution of a room controlled by a personal and portable cooler. As an energy saving strategy, the personal air-conditioning or task conditioning system was developed and installed in office buildings in the 90 s. Many research results regarding the personal air-conditioning (PAC) system were focused on thermal comfort, localized ventilation efficiency and energy savings. However, the conventional PACs were only developed for application in office buildings. In this study, as a type of PAC, a portable cooler was analyzed in terms of indoor temperature distribution changes with the passage of time. The measurement was performed in a bedroom in an apartment house. The results showed that indoor temperature was controlled at about $24^{\circ}C$ around the human body. However, the ambient zone up to 1.5 m away from the the human body stayed at about $27.5^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.878-882
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• 2016

These days, SFCLs are being developed in order to limit fault current. However, the superconducting elements that limit the fault current have such problems as capacity increase and require auxiliary devices including cooling device. If devices that comprise the current power network can withstand fault current for at least one cycle, it is possible to limit the fault current with current limiting elements by bypassing it on the fault line. In this study, the fault current limiter was configured with current transformer, vacuum interrupter, and current limiting element. Through the experience, it was confirmed that the fault current was limited within one cycle. The superconducting element, as a current limiting element, limited the fault current by 80 % within one cycle from fault occurrence, and the passive element limited it more than 95 %. Also, through the comparison between resistance curve and power consumption curve, it was confirmed that the current limiting element using a passive element was more stable than the superconducting element that required capacity increase and other auxiliary devices. It was considered that the FCL proposed in this study could limit fault current stably within one cycle from fault occurrence by using the existing power technologies such as fault current detection and solenoid valve operating circuit.

• Journal of IKEEE
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• v.19 no.4
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• pp.603-609
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• 2015

Thermal comfort is one of the fundamental aspects of indoor environmental quality and it is strongly related to occupant satisfaction and energy used in building. In this paper, we proposes smart comfort algorithm that save energy and provide a pleasant and comfortable environment for workers by the indoor comfort conditions(Predictive Mean Vote) detection and controlling the temperature and humidity, air flow. Simulation results, heating and cooling control of the thermal comfort control can be compared with the existing general air conditioners reduces the power of 0.5kW and indoor comfort can be maintained. Also, It showed a 49.2% improvement in the light by lighting control algorithm.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.11
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• pp.128-131
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• 1993

In order to get the basic data for the study of the heat stimulation of burning moxa, the pattern of combustion temperature, which is one of the important factors of thermal characteristics, was measured by density of cone moxa along the time procedure. The following results have been obtained 1) The pattern of combustion temperature by moxa burning was classified into input period which means the infiltration of heat into the area and output period which means the radiation of heat from the area. The input period consists of preheating and heating periods, while the output period consists of heat retaining and cooling periods. 2) The pattern of combustion temperature showed the same type or curve, which was not influenced by the moxa weight. However, Its pattern gradient are varied by density. It is considered that the pattern of combution temperature is primarily influenced by the rate of combustion temperature, gradient temperature and duration of combustion.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.343-344
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• 2010

화석연료의 고갈로 인하여 친환경 자동차에 대한 연구와 상용화가 급속도로 진행되면서 점점 대형 차종으로 그 범위가 넓어지고 있다. 대형 차종에 적용되는 전기동력 시스템의 MCU(Motor Control Unit), GCU(Generator Control Unit), DC/DC 컨버터 등과 같은 전장품도 그 용량이 커지면서 상용화를 위해 효율적인 측면도 많이 부각되지만 스위칭 소자, 변압기, 초크, 다이오드 등에서 동작으로 인해 열이 발생하고 제품의 구조상 밀폐된 공간에 장착이 되기 때문에 발열로 인한 동작의 신뢰성과 제품의 내구성에 큰 영향을 미치게 된다. 그중 가장 발열이 심한 IGBT(Insulated Gate Bipolar Transistor) 등과 같은 스위칭 소자에서 발생하는 열을 효과적으로 냉각시키기 위해 수냉구조가 필수적이며 동일한 조건의 수압, 유량에 보다 높은 방열특성을 가지기 위해 냉각구조에 대한 해석이 제품을 개발 전에 선행되어야 한다. 본 논문에서는 유로의 냉각핀 형상과 유로 구조에 따라 방열특성이 어떠한 차이가 있는지 시뮬레이션 프로그램을 통하여 비교하고, 모사발열체를 이용한 방열부의 냉각 성능 시험과 다이나모 환경의 최대 출력 시험을 통하여 방열 특성을 확인하였다.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.1
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• pp.15-21
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• 2008

Air-cooled split-type air conditioners (AC) are very popular in high-rise residential and commercial buildings in Korea. The performance of such AC systems varies significantly with system characteristics and environmental conditions. Particularly, the outdoor condensing unit of the system, if poorly cooled due to high density of AC distribution and restricted outdoor space, will result in large decrease of cooling efficiency and increase of electrical energy consumption and may further jeopardize the system reliability. This paper presents a numerical analysis on the thermal and energy performance of a group of air-cooled air conditioners installed at a courtyard of a high-rise building. The study introduces a series of new energy performance indices to assess the group performance of the AC condensers with different outdoor unit layouts. The results not only indicate the COP of the systems, but also quantify the system capacity and energy consumption. The evaluation method and indices developed are useful for guiding the design of the distribution plan of the AC units at building re-entrants.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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• pp.826-834
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• 2006

A heat sink system using nanofluidic thermosyphon for electronics systems was studied. The experimental results indicate that a cooling capacity of up to 150 W at an overall temperature difference of $50^{\circ}C$ can be attainable. The heat sink design program also showed that a computer simulation can predict the most of the parameters involved. In the experimental study, the volume concentration of nano particles affect the system performance. Nanofluidic thermosyphon with 0.5% volume concentration showed the best performance. Nanofluid can increase CHF of the system compared with water as a working fluid. The current simulation results were close to the experimental results in acceptable range. The simulation study showed that the design program can be a good tool to predict the effects of various parameters involved in the optimum design of the heat sink.