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나프탈렌과 다우섬 히트파이프의 작동 특성에 관한 실험적 연구
박기호(Ki-Ho Park),이영수(Young-Soo Lee),나호상(Ho-Sang Ra),장기창(Ki-Chang Chang) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
This paper is concerned with the heat transfer characteristics, the long-term operating of medium temperature range on the heat pipe. Working fluids used in the tests are Naphthalene, Dowtherm A. As a result, Dowtherm A as the working fluid have been proper at 200℃ to 300℃ temperature range, Naphthalene have been proper at 300℃ to 430℃temperature range. The heat pipe tested is made of SUS 316L tube of 27.2 ㎜ in outside diameter, 2.1 ㎜ in thickness and 700 ㎜ in length. Working fluid of about 40% of the inside volume of evaporator section of heat pipe is filled. In the case of the Naphthalene heat pipe, the heat transfer coefficient is 1520 W/㎡K , the heat transfer rate is 1300 W. In Dowtherm heat pipe the heat transfer rate is 1000 W.
순환루프에서 계면활성제의 마찰저감 퇴화 현상에 관한 실험적 연구
신광호(Kwang-Ho Shin),윤형기(Hyung-Kee Yoon),장기창(Ki-Chang Chang),나호상(Ho-Sang Ra),유성연(Seong-Yeon Yoo) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The objective of this study is to investigates phenomenon of surfactant drag reduction degradation by temperature and mechanical stress in circulation loop. The two kinds of degradation affected micelles or supermicellar structures in surfactant water solutions appear temporarily or permanently. The primary two factors of degradation by surfactant solution DR-IW 616 were experimentally studied. The interaction between degradation and the chemical materials - the biocide(Nalco 7331) and anticorrosive(NaNO₂) additives were also investigated.
GSHP용 수직형 지중열교환기의 열전달 성능에 관한 연구
정민호(Min-Ho Chung),장기창(Ki-Chang Chang),나호상(Ho-Sang Ra),백영진(Young-Jin Baik),박성룡(Seong-Ryong Park),유성연(Seong-Yeon Yoo) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
GSHP systems are used for air-conditioning systems in co㎜ercial buildings, schools, and factories because of low operating and maintenance costs. These systems use the earth as a heat source in heating and a heat sink in cooling mode. Ground heat exchangers are classified by a horizontal and vertical type according to the installation method. Vertical type is usually constructed by placing small diameter high density polyethylene tube in a vertical borehole. Vertical tube sizes range from 20 to 40 ㎜ nominal diameter. Borehole depth range between 100 and 200 m depending on local drilling conditions and available equipment. In this study, to evaluate the performance of single u-tube with bentonite grouting, single u-tube with broken stone grouting and double u-tube bentonite grouting of vertical ground heat exchangers, test sections are buried on the earth and experimental apparatus is installed. Therefore the heat transfer performance and pressure loss of these are estimated.