대형 공랭 포크형 히트파이프의 열전달 특성에 대한 실험적 연구 (Experimental Study on Heat Transfer Characteristics of a Large-Scale Air-cooled Fork-End Heat Pipe)

서지정보

· 발행기관 : 한국유체기계학회
· 수록지 정보 : 한국유체기계학회 논문집 / 21권 / 5호 / 34 ~ 42페이지
· 저자명 : 임창환, 김형대

초록

Recently, large-scale air-cooled heat pipes have been considered for use in various passive cooling systems to protect against station black-out accidents at nuclear power plants such as the one that occurred at the Fukushima facility in 2011. This study examines the conceptual design of a fork-end heat pipe (FEHP) with a relatively large heat transfer area in the condenser for air cooling in comparison to the evaporator for heating in liquid water. FEHP uses water as a working fluid and consists of one water-heated evaporator tube and several air-cooled condenser tubes. To experimentally evaluate the heat transfer characteristics of the proposed FEHP design, a scaled-down model and a test facility were constructed. The evaporator of the scaled-down model was heated by circulating hot water while the fork-end condensers were cooled by atmospheric air at room temperature. Results of this design study indicated that as the circulating water temperature was increased, four different operational modes were observed in the evaporator in sequence: natural convection, geyser boiling, fully-developed nucleate boiling, and falling film boiling. The geyser boiling displayed mechanically and thermally unstable features due to the large quantity of explosive nucleations in the working fluid when it was superheated beyond the saturation temperature corresponding to the system pressure.
The average heat transfer rate in the fully-developed nucleate boiling mode stably increased with increasing water temperature in the heating loop and converged towards a maximum value as the system approached the falling film boiling mode.

영어초록

Recently, large-scale air-cooled heat pipes have been considered for use in various passive cooling systems to protect against station black-out accidents at nuclear power plants such as the one that occurred at the Fukushima facility in 2011. This study examines the conceptual design of a fork-end heat pipe (FEHP) with a relatively large heat transfer area in the condenser for air cooling in comparison to the evaporator for heating in liquid water. FEHP uses water as a working fluid and consists of one water-heated evaporator tube and several air-cooled condenser tubes. To experimentally evaluate the heat transfer characteristics of the proposed FEHP design, a scaled-down model and a test facility were constructed. The evaporator of the scaled-down model was heated by circulating hot water while the fork-end condensers were cooled by atmospheric air at room temperature. Results of this design study indicated that as the circulating water temperature was increased, four different operational modes were observed in the evaporator in sequence: natural convection, geyser boiling, fully-developed nucleate boiling, and falling film boiling. The geyser boiling displayed mechanically and thermally unstable features due to the large quantity of explosive nucleations in the working fluid when it was superheated beyond the saturation temperature corresponding to the system pressure.
The average heat transfer rate in the fully-developed nucleate boiling mode stably increased with increasing water temperature in the heating loop and converged towards a maximum value as the system approached the falling film boiling mode.

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