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평판형 히터를 이용한 나노 유체 풀비등 임계열유속의 실험적 연구
안호선(Ho Seon Ahn),김선태(Seontae Kim),조항진(Hangjin Jo),제준호(JunHo Je),김무환(Moo Hwan Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The flat plate experimental apparatus supporting only thermal heating was developed to perform the CHF enhancement experiment with nanofluids in pool boiling. Nickel and copper surface was used as heater surfaces and nanofluids was created with A1₂O₃, TiO₂ nanoparticles and deionized water by 2-step methods. And CHF in deionized water enhance on nanoparticles deposited surface. So, CHF enhancement in nanofluids is also achieved by the surface effect. CHF enhancement quantities are different as a kind of surface. Copper surface have more CHF enhancement than nickel in same nanofluids. And boiling in A1₂O₃, TiO₂ nanofluids made different surface shape. Surface investigation (SEM) about the nanoparticles coated surface was performed. And these different surfaces induced a different CHF enhancement ratio.
조기현(Kee-Hyeon Cho),안호선(Ho-Seon Ahn),김무환(Moo-Hwan Kim) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.1
본 연구에서는 3 차원 전산 열유동해석을 통하여 형상법칙에 근거하여 개발된 냉각판의 열수력학적인 특성을 분석하였다. 서펜타인 형상을 포함하여 최적화, 최적화되지 않은 1, 2 차 형상 총 5 개 형상을 대상으로 동일한 구속조건을 부여함으로써 유동저항, 열저항 및 분지유로에서의 유동균일도를 상호 비교함으로써 냉각판의 성능평가를 수행하였다. 그 결과, 최적화된 1, 2 차 형상 구조가 최적화되지 않은 경우와 비교하여 훨씬 적은 압력손실을 나타내었으며, 압력손실을 기준으로 최적화된 2 차 형상 구조가 가장 우수한 유동 구조를 나타내었다. 또한, 최적화된 1, 2 차 형상구조의 열저항 및 유동 분배성능도 기존에 사용되는 유로형상과 비교하여 모두 우수한 성능을 보였다. In this study, we investigated the hydrodynamic and thermal performance of constructal architectures on the basis of the mass flow rates for a given pressure drop, and we determined the thermal resistance and flow uniformity. The five flow configuration used in this study were the first construct with optimized hydraulic diameter, the second construct with optimized hydraulic diameter, the first construct with non-optimized hydraulic diameter, second construct with non-optimized hydraulic diameter, and a serpentine configuration. The results of our study suggest that the best fluid-flow structure is the second constructal structure with optimized constructal configurations. We also found that in the case of the optimized structure of cooling plates, the heat transfer was remarkably higher and the pumping power was significantly lower than those of traditional channels.
조기현(Kee-Hyeon Cho),안호선(Ho Seon Ahn),김무환(Moo-Hwan Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
In this study, we investigated the hydrodynamic and thermal performance of constructal architectures based on the mass flow rates for the given pressure drop and identify the required pumping power and thermal resistance. The five flow configurations described in this paper are the first, second constructs with optimized hydraulic diameters and nonoptimized hydraulic diameter, respectively, including the serpentine configuration. The results suggest that best fluid flow structure is the second constructal structure with optimized constructal configurations. We also found that the optimized structure of cooling plates could enhance heat transfer remarkably and decrease pumping power dramatically compared with the traditional channels.
증기폭발 압력 하중에 대한 마이크로 버블 군집의 저감 효과 연구
김찬우(Chanwoo Kim),박현선(Hyun Sun Park),안호선(Ho Seon Ahn) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Steam explosion is a phenomenon which can threat the integrity of the containment structure with high pressure impulses when the molten core drops into a water pool either inside or under the reactor vessel bottom during a severe accident of a light water reactor. For suppressing steam explosion, we focus on the shock wave mitigation effect by microbubble clouds, i.e. the shock-bubble interaction (SBI). Using the SBI model which describes one-dimension shock tube containing bubbly liquid with microbubble clouds, dissipation energy (DE) and damping time (DT) are obtained, which are major indicators of shock mitigation under the microbubble-liquid media. To apply the SBI model to large scales such as steam explosion, candidates of shockwaves from steam explosion are listed for this research from previous researches conducting the steam explosion. Finally, moving distances of the shockwaves are calculated and discussed for shock mitigation.
나노유체 이용한 풀비등 임계열유속 증가에서 나노입자 유착물의 영향에 관한 실험적 연구
김형대(Hyung Dae Kim),김선태(Seon Tae Kim),안호선(Ho Seon Ahn),김무환(Moo Hwan Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
It has been well known that pool boiling CHF in nanofluids compared to pure water significantly increase due to the deposition of nanoparticles on heater surface. This study concerns the characteristics of the nanoparticle deposition layer and its influence on CHF. Pool boiling experiments were carried out with 0.01.% water-TiO₂ nanofluids to obtain various nanoparticle-deposited heaters. CHF on the prepared heaters was measured during pool boiling in pure water. The heater surfaces were visualized using scanning electron microscope (SEM) and also characterized using contact angle and capillarity. The results showed that the CHF enhancement in nanofluids was completely dependent upon the structural and physicochemical characteristics of the nanoparticle deposition layer.
마이크로/나노 사이즈의 표면 개질을 통한 풀 비등 임계열유속 향상을 위한 실험적 연구
김선태(Seontae Kim),김형모(Hyungmo Kim),안호선(Ho Seon Ahn),조항진(Hangjin Jo),김준원(Joonwon Kim),김무환(Moo Hwan Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
It is well known that modifying the geometry or characteristics of heater surface is one of the effective ways in enhancing CHF. Also many researchers have been struggling to develop fine and fancy heater surface by various methods so far. Lately, there were lots of research about enormous CHF enhancement with nanofluids, which is well dispersed fluid with nano-sized particles, and it was proved that this phenomenon definitely depends on deposition of nanoparticle over heater surface. We have observed micro/nano multi-scale geometry and high wettability characteristic on naturally developed nanoparticle deposited heater surface from boiling experiment with nanofluid. On the base of this observation, we made micro/nano multi-scale surface with good wettability by MEMs technique, and conducted CHF experiments with them.
실리콘 표면 위에 소수성 점을 이용한 비등 열전달 증진에 관한 실험적 연구
조항진(Hang Jin Jo),김형모(Hyungmo Kim),안호선(Ho Seon Ahn),강순호(Soonho Kang),김준원(Joonwon Kim),신정섭(Jeong-Seob Shin),김무환(Moo Hwan Kim) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.6
표면 젖음성은 비등 상황에서 주요 인자인 임계열유속과 비등열전달 모두에 영향을 미치는 중요한 표면인자이다. 지금까지 표면 젖음성을 이용한 비등 조건 개선에 대한 연구는 한가지 물질의 표면 구조를 개질하는데 국한되었다. 본 논문에서는 최적화된 비등 조건을 이룰 수 있는 표면 젖음성을 찾기 위한 연구의 일환으로 소수성 물질과 친수성 물질의 혼합을 시도하였다. 가열 표면은 표면 접촉각이 60° 인 친수성 표면위에 표면 접촉각 120° 의 소수성 물질 점이 생기도록 개질되었다. 개질된 소수성 점은 마이크로 단위와 밀리 단위로 그 크기를 변화시켜 가며 풀 비등 성능을 평가하였다. Wettability is important to enhance not only CHF but also nucleate boiling heat transfer, as shown by the results of different kinds of boiling experiments. In this regard, an excellent boiling performance (a high CHF and heat transfer performance) could be achieved in the case of pool boiling by some favorable surface modifications that can satisfy the optimized wettability condition. To determine the optimized boiling condition, we design special heaters to examine how two materials, which have different wettabilities (e.g., hydrophilic and hydrophobic materials), affect the boiling phenomena. The special heaters have hydrophobic dots on a hydrophilic surface. The contact angle of the hydrophobic surface is 120° to water at the room temperature. The contact angle of the hydrophilic surface is 60° at same conditions. Experiments involving micro hydrophobic dots and two types of milli hydrophobic dots are performed, and the results are compared with a reference surface.