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Effect of hole shape on the heat transfer in a rectangular duct with perforated blockage walls
신소민,곽재수 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.10
Heat transfer coefficients were measured by the improved hue detection based liquid crystal technique in a turbine blade internal cooling passage model with blockage walls. In the experiments, blockages with 9 holes of circular, wide, narrow shapes were used and for the circular shape, the number of hole of 7, 9, and 11 were tested. For all cases, the perforated area was kept same. Results showed that the staggered impingement jets increased heat transfer coefficient, however, pressure drop also increased greatly. Generally, Nusselt number ratio and the thermal performance factor decreased as Reynolds number increased. For all Reynolds numbers tested, the blockage wall with wide holes gave more uniform heat transfer coefficient and higher thermal performance factor. As the number of hole increased from 7 to 11, the distribution of heat transfer coefficient became uniform and the thermal performance factor increased.
신소민,이기선,박승덕,곽재수 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.3
Heat transfer coefficients were measured in a channel with one side dimpled surface. The sphere type dimples were fabricated, and the diameter (D) and the depth of dimple was 16 mm and 4 mm, respectively. Two channel heights of about 0.6D and 1.2D, two dimple configurations were tested. The Reynolds number based on the channel hydraulic diameter was varied from 30000 to 50000. The improved hue detection based transient liquid crystal technique was used in the heat transfer measurement. Heat transfer measurement results showed that high heat transfer was induced downstream of the dimples due to flow reattachment. Due to the flow recirculation on the upstream side in the dimple, the heat transfer coefficient was very low. As the Reynolds increased, the overall heat transfer coefficients also increased. With the same dimple arrangement, the heat transfer coefficients and the thermal performance factors were higher for the lower channel height. As the distance between the dimples became smaller, the overall heat transfer coefficient and the thermal performance factors increased.
이중 충돌 제트를 갖는 사각 덕트 내의 열전달 계수 측정
신소민(Somin Shin),이기선(Ki Seon Lee),박승덕(Seoung Duck Park),곽재수(Jae Su Kwak),차봉준(Bong Jun Cha) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Heat transfer coefficients were measured by the improved hue detection based on liquid crystals technique in a turbine blade internal cooling passage model with three blockage walls. In the experiments, blockages with 9 holes of circular, wide, narrow shapes were used and for the circular shapes, holes number of 7, 9, and 11 were tested. For all cases, the total perforated area was kept same. Results showed that the staggered impingement jets increased heat transfer coefficient, however, pressure drop also increased greatly. Generally, Nusselt number ratio and the thermal performance factor decreased as Reynolds number increased. For all Reynolds numbers tested, the blockage wall with wide holes gave more uniform heat transfer coefficient and higher thermal performance factor. As the number of hole increased from 7 to 11, the distribution of heat transfer coefficient became uniform and the thermal performance factor increased.
지구 저궤도에서 운용되는 영상센서를 위한 열설계 및 열해석
신소민(Somin Shin),오현웅(Hyun-Ung Oh) 한국항공우주학회 2011 韓國航空宇宙學會誌 Vol.39 No.5
지구의 저궤도에서 운용되는 영상센서는 극저온 환경에서 태양 복사 뿐 아니라 지구의 적외선 및 알베도(Albedo)의 영향을 받는다. 극한 환경에 노출되는 영상센서는 작동/비작동시 허용 온도를 벗어나지 않도록 열설계가 필요하며, 정상상태 에너지 평형식을 통해 필요한 방열판 면적 및 히터 예비 설계 값을 설정한다. 일반적으로 위성체 패널에 주기를 갖는 발열장비가 장착되어, 패널의 일부를 방열판 면적으로 설계한다. 본 논문에서는 위성체와 분리하여 설계하는 영상센서의 열제어를 위하여, 내부에서 항상 발열하는 장비의 열을 히트파이프를 이용하여 패널에 장착된 방열판으로 효과적으로 전달하도록 설계하였다. 예비 설계값을 기준으로 수치해석에 기반을 두는 SINDA를 이용하여 궤도 열해석을 실시하여, 방열 면적 및 히터 설계는 쉽고 빠르게 계산되어졌다. 또한, 방열 성능을 유지하면서 질량을 줄이도록 방열판을 립형상(Rib-type)으로 설계하였으며, 궤도 열해석 결과, 영상센서의 열적 요구사항을 만족함을 검증하였다. Space Imaging Sensor operated on LEO is affected from the Earth IR and Albedo as well as the Sun Radiation. The Imaging Sensor exposed to extreme environment needs thermal control subsystem to be maintained in operating/non-operating allowable temperature. Generally, units are periodically dissipated on spacecraft panel, which is designed as radiator. Because thermal design of the imaging sensor inside a spacecraft is isolated, heat pipes connected to radiators on the panel efficiently transfer dissipation of the units. First of all, preliminary thermal design of radiating area and heater power is performed through steady energy balance equation. Based on preliminary thermal design, on-orbit thermal analysis is calculated by SINDA, so calculation for thermal design could be easy and rapid. Radiators are designed to rib-type in order to maintain radiating performance and reduce mass. After on-orbit thermal analysis, thermal requirements for Space Imaging Sensor are verified.