• Architectural research
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• 제17권3호
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• pp.109-115
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• 2015

The dynamic pricing of electricity, where the electricity rate increases in a time zone with a high demand for electricity is typically applied to a building whose power reception capacity is greater than a certain size. This includes the time of use(TOU) electricity pricing in Korea which can induce the effect of reducing the power demand of a building. Meanwhile, a VRF (Variable Refrigerant Flow) system that uses electricity is regarded as one of the typical heating and cooling systems along with central air conditioning (central HVAC) for its easy operation and application to the building. Thus, to reduce power energy and operating costs of a building in which the TOU and VRF systems are applied simultaneously, we suggested a control for changing the indoor temperature setting within the thermal comfort range or limiting the rotational speed of an inverter compressor. In this study, to describe the features of the above-mentioned control and verify its effects, we evaluated the results obtained from the analysis of its operation data. Through the actual measurements in winter operations for 73 days since mid- December 2014, we confirmed a reduction of 10.9% in power energy consumption and 12.2% in operating costs by the new control. Also, a reduction of 13.3% in power energy consumption was identified through a regression analysis.

• Restorative Dentistry and Endodontics
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• 제41권4호
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• pp.316-321
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• 2016

Although it is challenging, the early diagnosis of a vertical root fracture (VRF) is crucial in order to ensure tooth preservation. The purpose of this clinical case report was to describe reparative surgery performed to treat a tooth affected by an incomplete VRF. A 26 year old male patient was suspected to have a VRF in a maxillary left central incisor, and an exploratory flap was performed in order to confirm the diagnosis. After detecting the fracture, the lesion was surgically treated, the fracture and the infected root-end were removed, and a platelet-rich plasma membrane was used to cover the defect in order to prevent bacterial migration. A 24 month clinical and radiological follow-up examination showed that the tooth was asymptomatic and that the healing process was in progress. The surgical approach described here may be considered an effective treatment for a combined endodontic-periodontal lesion originating from an incomplete VRF and a recurrent periapical lesion.

• 대한기계학회논문집 C: 기술과 교육
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• 제3권1호
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• pp.1-13
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• 2015

실외 열교환기의 착상 및 제상조건 하에서 VRF 멀티형 히트펌프의 동적 거동의 해석을 위한 시뮬레이션 기법이 제안되었다. 이를 위해 열전달-물질전달 완벽 상사 가정에 기반한 간단한 착상모델과 제상 모델이 제안되었다. 제안된 착제상 모델은 용량가변 압축기 모델과, 미소면적에 대한 열 및 모멘텀 평형에 근거한 열교환기 모델을 채택한 동적 사이클 해석모델에 적용되었다. 따라서, 제안된 모델은 공간에 대해 비균질 착상을 자연스럽게 예측할 수 있다. 개발된 동적 사이클 해석 모델은 실험결과와 비교하여 능력 및 효율을 10% 이내에서 잘 예측함을 확인하였다. 최종적으로, 개발된 모델은 표준적인 건물의 난방시즌 운전 해석에 적용되었으며, 착상 및 제상으로 인하여 동절기의 계절 성능계수를 7% 가량 하락 시킴을 보일 수 있었다.

• Architectural research
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• 제19권3호
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• pp.71-77
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• 2017

Dynamic pricing refers to a system in which a tariff varies, according to a level of charging and applied time depending on time change. The power billing system used in the Korean Electric Power Corporation (KEPCO) is based on time of use (TOU) pricing, which is one of the dynamic pricing systems. This paper aimed to determine the operational results of a variable refrigerant flow system, to which a new control algorithm was applied, in order to respond to dynamic pricing, in summer and the utility of the new control. To do this, real measured data was acquired from a VRF system installed in a building for educational purposes, where dynamic pricing was applied for about 100 days during summer time. At the maximum load operation time period in TOU, the new control minimized operation within the indoor comfort range, an increase in refrigerant evaporation temperature in the indoor unit and the number of revolutions in a compressor in the outdoor unit was limited. As a result, power usage was decreased by 11%, and the operational cost by 14.6%. Furthermore, measurement results using the Predicted Mean Vote (PMV) model, that represented satisfaction of thermal environment, showed that 82.8% to 90.4% of the occupants of the building were satisfied during operation when the new control was applied.

• 한국지열·수열에너지학회논문집
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• 제14권4호
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• pp.27-34
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• 2018

This study compared constant water bath performances of conventional water-cooled refrigerator and electric heater with an air-cooled VRF chiller and electric heater equipped with optimal control algorithm. In heating mode, the air cooled VRF chiller and electric heater combination reduced the set temperature arrival time by an average of 42 minutes, and energy was also reduced by 18%. In cooling mode, the two systems took 70 minutes to reach the set temperature and showed no difference. Energy was reduced by 33.5% with the new system. For constant temperature maintaining experiment, after reaching the set temperature of $15^{\circ}C$, $20^{\circ}C$ and $22^{\circ}C$, temperature deviations were all in the range of $-0.2^{\circ}C$ to $+0.1^{\circ}C$. Energy was reduced by an average of 84.9%. Through this study, possibility of precise temperature control by an air cooled VRF chiller system was confirmed.

• 대한설비공학회지:설비저널
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• 제39권12호
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• pp.43-49
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• 2010

• 대한설비공학회지:설비저널
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• 제44권12호
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• pp.58-63
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• 2015

• 지열에너지저널
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• 제4권2호
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• pp.53-62
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• 2008

• 대한설비공학회지:설비저널
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• 제45권12호
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• pp.64-68
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• 2016

• 지열에너지저널
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• 제4권4호
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• pp.52-58
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• 2008