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루프식 히트파이프의 수직 평판형 증발부 내부 열전달계수의 특성에 관한 연구
최윤덕(Yun Deok Choi),부준홍(Joon Hong Boo),한창우(Chang Woo Han),정승붕(Seung Boong Jeong) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12
Experimental investigation was conducted on the convective heat transfer coefficient in a vertical flat-plate evaporator of a loop-type heat pipe, of which the working fluid was distilled water. The evaporator was made of copper and the heating area dimensions were 190×114 ㎟. The condenser was an air-cooled fin-tube heat exchanger. Heat flux was varied from 5 to 139 kW/㎡, while the evaporator was maintained below 100°C. Three different evaporator surface conditions were compared: bare surface, screen mesh covered, and hybrid wick covered. The wick-covered surfaces exhibited distinctly higher heat transfer to bare surface, for heat fluxes higher than 88 kW/㎡. The bare surface showed moderately higher heat transfer coefficients for heat fluxes up to 69 kW/㎡, but decreased thereafter and eventually resulted in overheating at 106 kW/㎡. The surface with a hybrid wick exhibited a heat transfer coefficient of 10,300 W/㎡·K at a heat flux of 139 kW/㎡.
전력반도체 모듈 냉각용 루프식 열사이펀에서 충전률이 작동 특성에 미치는 영향
배장현(Jang Hyun Bae),조영탁(Young Tak Cho),최윤덕(Yun Deok Choi),부준홍(Joon Hong Boo),한창우(Chang Woo Han),정승붕(Seung Boong Jeong) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
A series of experiments was conducted to investigate the operational characteristics of a loop-type thermosyphon for cooling of a power transistor module under high heat flux. The flat evaporator was made of copper and the heating area was 150 ㎜ × 190 ㎜, and the working fluid was water. The transport lines were made of polyethylene tubes and the inner diameters of the vapor and liquid lines were 16.0 ㎜ and 12.4 ㎜, respectively. The condenser was a fin-tube heat exchanger cooled by forced air convection. The condenser was separated from the evaporator by 1.3 m horizontally, and positioned 0.6 m higher to utilize the gravity for liquid return. The thermal performance varied greatly with the working fluid fill charge. For a fill charge ratio of 60%, the loop thermosyphon transported a maximum heat load of 3.3 ㎾ maintaining the evaporator temperature below 100℃, with air cooling at room temperature.
평판형 증발부를 갖는 루프히트파이프에서 작동유체 충전량이 열성능에 미치는 영향
조영탁(Young Tak Cho),배장현(Jang Hyun Bae),최윤덕(Yun Deok Choi),부준홍(Joon Hong Boo) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Effect of fluid inventory on the performance of a loop heat pipe (LHP) with a flat evaporator was experimentally investigated. The evaporator wall and tubing were made of STS316 and the effective heating area was 40 × 42 ㎟. The working fluid was methanol. Sintered nickel wick was used as a capillary structure of which the pore size and porosity were 2.7 ㎛ and 55% respectively. The length of the fluid transport line was 0.6 m and the maximum heat flux was 17.9 W/㎠. Fluid inventory was determined by considering the relative charge ratio of the compensation chamber and condenser. In order to investigate the effect of fluid inventory on thermal performance of the LHP, a series of experiments was conducted for adverse as well as positive tilt angles.
평판형 증발부를 갖는 루프히트파이프의 역구배 성능에 대한 실험적 연구
임경택(Kyung Taek Im),배장현(Jang Hyun Bae),조영탁(Young Tak Cho),최윤덕(Yun Deok Choi),부준홍(Joon Hong Boo) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
The performance at the adverse tilt of a loop heat pipe(LHP) with a flat square evaporator was experimentally investigated. The LHP was made of stainless steel and methanol was used as working fluid. The maximum heat load was 300 W(heat flux of 19 W/㎠) and its heating area was 40 ㎜ × 40 ㎜. The coolant inlet temperature at the condenser was maintained at 10℃. The LHP operated successfully at the adverse tilt angle of 90˚ for the heat load range of 38 W to 240 W. A cold start-up was demonstrated for a step heat input of 183 W. Sintered nickel was used as a capillary structure in the evaporator. The lowest thermal resistance was 0.186℃/W.
최윤덕,이드보라,박성욱,강미선,왕한영 대한피부과학회 2002 大韓皮膚科學會誌 Vol.40 No.12
Basal cell carcinoma(BCC) is the most common cancer of the skin in Korea. The lesions are most frequently found in the head and neck regions. However, its appearance on the scrotal skin is rare. We observed a case of pigmented BCC on the scrotum in a 66-year-old man. He had a well circumscribed, brown-black plaque on the scrotum for 5 years and the history of prior vasectomy about 30 years ago. The cancer was excised widely. (Korean J Dermatol 2002;40(12) : 1571∼1573)
유두상 한선낭종, 모모세포종, 기저세포암, 피지선종, 피지선 상피종을 동반한 피지선 모반 1예
최윤덕,이드보라,박성욱,강미선,하동호,왕한영 대한피부과학회 2003 大韓皮膚科學會誌 Vol.41 No.1
Nevus Sebaceus is a hamartoma that has a welt-documented neoplastic potential. Multiple tumors may occasionally arise, but the coexistence of 3 or more tumors is extremely rare. We report a case of nevus sebaceus in a 55-year-old female associated with syringocystadenoma papilliferum, trichoblastoma, basal cell carcinoma, sebaceous adenoma and sebaceous epithelioma. (Korean J Dermatol 2003;41(1) : 129∼131)
최윤덕,이드보라,박성욱,왕한영 대한피부과학회 2003 大韓皮膚科學會誌 Vol.41 No.2
Despite numerous therapeutic options the treatment of verruca vulgaris remains difficult and various treatment modalities are accompanied with substantial pain, tissue destruction and frequent recurrence. Recently imiquimod has been successfully used as topical immune response modifier for the treatment of external anogenital warts with less pain, destruction and fewer recurrent rate. We observed a case of verruca vulgaris on the left palm and the left second toe in a 57-year-old man. He had been treated with keratolytic agent and CO_2 laser with little effect. So we tried to treat him with 5% imiquimod cream which was self-applied to the lesions and achieved complete clearance after 4 weeks of the therapy (Korean J Dermatol 2003;41(2) : 261∼263)