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계면활성제가 첨가된 관내 난류의 열유동 특성에 관한 고찰
신광호(Kwang-Ho Shin),윤형기(Hyung-Kee Yoon),장기창(Ki-Chang Chang),나호상(Ho-Sang Ra) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.6
The fluid mechanics and heat transfer of surfactant turbulent pipe flows are characterized with particular emphasis on the effects of surfactant concentration and solution temperature on drag reduction and heat transfer reduction. The test fluids are the surfactant solutions of DR-IW616 supplied by Akzo Nobel Chemical in concentration of 100~3000 ppm. The solution temperatures studied are 5℃ to 50℃. The critical values of surfactant concentration and solution temperature are clearly identified for drag reduction phenomena.
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.
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.
중온 지열수를 이용한 고온제조 열펌프 시스템 해석 및 설계
김민성(Kim, Min-Sung),백영진(Baik, Young-Jin),박성룡(Park, Seong-Ryong),장기창(Chang, Ki-Chang),이영수(Lee, Young-Soo),나호상(Ra, Ho-Sang) 한국신재생에너지학회 2008 한국신재생에너지학회 학술대회논문집 Vol.2008 No.05
Geothermal water at moderate temperature in a range between 30 to 50?C exists sparse in surroundings. Mostly they are utilized as heat or water source at spar zones in Korea. However, a large portion of used water is discarded due to its poor recovery quality and inferior application technologies. In this research, an innovative heat pump system based on the hybrid concept that combinate compression cycle and absorption cycle was investigated mathematically. The hybrid heat pump aims to recycle various kind of the heat sources at moderate temperature including geothermal water effectively. The prime objective of the simulation is to design a compression/absorption hybrid heat pump system which can make high temperature above the level of 90?C and low temperature of 20?C as well at the same using 50?C geothermal heat water. As a result, primitive data was provided as a basis to design a prototype 3 RT class hybrid heat pump.