• 한국산학기술학회논문지
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• 제12권1호
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• pp.68-73
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• 2011

본 논문에서는 서로 다른 종류 또는 다수의 동일 가전기기를 그룹별로 관리할 수 있는 HBS(Home Bus System)을 분석하고, 기존의 독립된 제어시스템으로 중앙제어기를 구축하던 방식을 PC로 대체한 새로운 방식의 HBS 시스템을 설계하였다. 설계한 시스템은 빌딩에 설치된 에어컨을 통제실 또는 사무실에서 모니터링 및 제어할 수 있어 에너지를 효율적으로 관리할 수 있게 되었으며, 향후 유사 대규모 가전기기 통합 및 개별관리에 적용할 수 있어 홈오토메이션 구축에 크게 기여할 것으로 기대된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1009-1011
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• 2001

This paper presents a new hybrid control scheme using Active-Clamped Class-E (ACCE) inverter of induction heating(IH) jar for high power applications. The proposed hybrid control scheme has characteristics, which act as class-E inverter at lower switch voltage and ACCE inverter at higher switch voltage than reference voltage of the main switch by feeding back voltage one as well as advantages of conventional ACCE inverter such as zero-voltage switching(ZVS) of the main switch and the reduced switch voltage due to the clamping circuit. Moreover, the proposed control method makes higher output power than conventional ACCE inverter control one since ACCE inverter is operated like class-E inverter at low voltage condition. The principle of the proposed control are explained in detail and the validity of the proposed control scheme is verified through the several interesting simulated and experimental results.

• 한국환경보건학회지
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• 제32권4호
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• pp.268-274
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• 2006

In this study in order to evaluate the growth of RF propagation exposure rate generated according to the enhancement of its use, it is proposed for the ground to be able to examine and to contemplate the correlation between the human health and RF propagation exposure rate by measuring and analyzing the RF exposure source and exposure rate in an indoor environment. As a result of research, it is analyzed that the main exposure source of critically making effect in indoor environment is the frequency hand if radio broadcasting, mobile communication, wireless LAN, digital broadcasting, home appliance, etc., including the TV broadcasting. Among these, it is shown that the TV broadcasting and mobile communication band are the highest. And it is the concluded that RF exposure rate of the environmental sensitive equipment, like an institution for the aged, has lower possibility to exceed the human RF protection criteria by this evaluation.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.1019-1029
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• 2006

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.1059-1067
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• 2006

In order to develop a compact evaporator, experiments that show characteristics of evaporating heat transfer and pressure drop in the helically coiled minichannel were performed in our previous research. This study was focused on the performance analysis of helically coiled heat exchangers with circular minichannels with an inner diameter=1.0 mm. The working fluid was R-22, and the properties of R-22 were estimated using the REFPROP program. Numerical simulation was performed to compare results with the experimental results of the helically coiled heat exchanger. As the heat transfer rate and pressure drop were calculated at the micro segment of the branch channels, the performance of the evaporator was evaluated. The following conclusions were obtained through the numerical simulations of the helically coiled heat exchanger. It showed good performance when the flow rate of each branch channels was suitable to heat load of air-side. The numerical simulation value agreed with experimental results within ${\pm}15%$. In this study, a numerical simulation program was developed to estimate the performance of a helically coiled evaporator. And, an optimum helically coiled minichannels evaporator was designed.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.590-595
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• 2009

PMV and ADPI were numerically investigated in a large space of various ceiling height with air-conditioning systems of two type. The numerical results showed that it is small that the growth of cooling load according to ceiling height rise in a large space without windows. In case of system air-conditioner of duct type embedded in the ceiling, the air mixing effect in indoor is superior to a case installed 4way cassette type in it. For controling thermal comfort at indoor, a system air-conditioner of duct type embedded in the ceiling is little influenced according to ceiling height rise in a large space considered.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1067-1072
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• 2009

In vapor compression systems which use refrigerant as a working fluid, the oil is commonly used for compressor lubrication. Since the presence of lubrication oil can change the characteristics properties of refrigerant, the oil affects the heat transfer performance of heat exchanger to a large extent. In this paper, we focus on the effect of PVE oil experimentally on heat transfer performance of the fin-tube heat exchangers which use R410A as a refrigerant. To evaluate the heat transfer performance, the refrigerant to air type test facility chamber has been used. Fin-tube heat exchanger with grooved has been tested while according to the oil mass fraction variation from nearly zero to 1.7 wt%. It was found that the low level of oil mass fraction has an obvious effect on heat transfer performance, while the high level seems no significant influence. The influence of the oil mass fraction to heat transfer performance, however, is different between evaporation and condensation.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1073-1078
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• 2009

Finned-tube heat exchangers are often made with aluminum fins and copper tubes. Usually the contact between fin collar and tube surface for finned tube heat exchanger is secured by mechanical expansion of the tubes. The objective of the present study is to apprehend how much effect clearance has on the performance of heat exchanger. This effect is studied using an experimental approach. The thermal fluid measurements are made using a psychometric calorimeter. Frontal air velocity varies in the range from 1.0m/s to 3.0 m/s. The heat transfer rate of sample which has bigger clearance is only 27% compare with the other's in dry condition. In wet condition, its heat transfer rate is 78% compare with the other's.

• 설비공학논문집
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• 제25권3호
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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.

• 한국산업보건학회지
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• 제18권1호
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• pp.1-10
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• 2008

In order to evaluate performance of anti-vibration gloves, it is necessary to measure the transmitted vibration to the hand and the applied forces at the same time while gripping the vibrating handle. In the study a system was developed to measure both the vibration and the forces. The system consists of a measurement handle with eight strain gauges and two accelerometers and a PC-based system with a software for signal processing, evaluation of the hand-transmitted vibration and for control of applied forces in the pre-determined range. The handle was installed on the vibration shaker which is strong enough so as not to be affected by dynamic coupling with the hand-arm. Whole procedure of ISO 10819:1996 to determine the vibration transmissibility of anti-vibration gloves was programmed into the system. As an example of the application, three subjects joined the test to get vibration transmissibilities of 9 anti-vibration gloves where each glove was tested twice a subject. Average and standard deviation of the corrected vibration transmissibility were also calculated. All tested gloves fulfilled criterion for M-spectrum($\overline{TR_M}$<1.0), but one glove fulfilled criterion for H-spectrum($\overline{TR_H}$<6.0),