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고한서,김용재,Ko, Han-Seo,Kim, Yong-Jae The Korean Hydrogen and New Energy Society 2006 한국수소 및 신에너지학회논문집 Vol.17 No.2
A high-speed and initial helium jet flow has been analyzed by a developed four-dimensional digital speckle tomography. Multiple high-speed cameras have been used to capture movements of speckles in multiple angles of view simultaneously because a shape of a nozzle for the jet flow is asymmetric and the initial jet flow is fast and unsteady. The speckle movements between no flow and helium jet flow from the asymmetric nozzle controlled by a solenoid valve have been obtained by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. The four-dimensional density fields for the high-speed helium jet flow have been reconstructed from the deflection angles by a developed real-time tomography method.
송찬(Chan Song),고한서(Han Seo Ko) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
As display-based products develop, they are good to use in various situations. However, it was confirmed that LCD display panels used outdoors were damaged when subjected to excessive heat. Typically, blackening, gravity mura, and yellowing damage occur. This damage shortens the display life and makes uncomfortable on users. To reduce such damage, various methods such as PCM (Phase change Material), forced convection cooling and Trombe wall are used. In this study, the thermal management methods were tested. The PCM, Trombe wall, and forced convection were compared for the outdoor display thermal management system. As a result of analyzing the temperature of the display, it was found that the cooling performance was better when Trombe wall and fan were combined with the PCM.
기포 주입 위치에 따른 기포와 상변화물질의 유동 상호 작용 연구
김민혁(Min Hyeok Kim),고한서(Han Seo Ko) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11
In this study, the optimization of the bubble injection position to the phase change material (PCM) was investigated, and the bubble behavior was analyzed using shadowgraphy. The shape and size of rising bubbles varied depending on the position of the injection when the solid PCM was liquefied from the heated vertical wall. We tracked the rising paths over time based on the bubble injection position and bubble size. When the bubble immediately rose, it exhibited elliptical shape and zigzag path. Conversely, when the bubble rose after merging at the bottom of the solid PCM, as the equivalent diameter for the inter-wall distance was 0.64 or more, it exhibited a jellyfish-like shape and strong rocking behavior. As the wall spacing increased, the bubble transformed into elliptical shape, reducing rocking behavior, and went up in a zigzag path. The results clearly indicate that the injection position significantly influences characteristics such as the size, shape, and rising trajectory of bubble.
태양 에너지 발전 효율 증대를 위한 PVT 패널 내부 유동에 관한 실험적 연구
서민준(Min Jun Seo),고한서(Han Seo Ko) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Renewable energy generation has increased and will increase about 10 times in 30 years. Since solar energy accounts for a significant part of renewable energy production, increase of efficiency is important. There are 2 ways to use solar energy, photovoltaic and solar thermal panel. The combination of those ways is called photo voltaic thermal (PVT) panel which simultaneously obtains electricity and thermal energy from the sun. This study deals with a PVT panel composed of a phase change material (PCM) and a heat exchanger in PV panel. The water is used as heat exchanger fluid and change in flow rate causes change in thermal energy output. In this experiment, by comparing between 30LPM and 60LPM flow rate, 60LPM flow rate results in 7.3 % high in thermal energy output.