学　术

　　本次讲座，航空航天学院特别邀请韩国釜山国立大学教授、韩国工程院Kyung Chun Kim院士，与我校师生分享他的研究心得。具体安排如下，欢迎感兴趣的师生参加：

　　时　间：2019年3月1日（周五）上午10:00-12:00

　　地　点：研究院大楼202会议室

　　主　题：Complex fluid-flows through stochastic porous media

　　主讲人：Kyung Chun Kim，釜山国立大学教授、韩国工程院院士

　　Prof. K. C. Kim received MS and Ph.D degree at KAIST, Korea in 1981 and 1987 respectively. Since 1983, he was hired as a faculty member in Pusan National University (PNU). He was a visiting professor of Ottawa University in 1989-1990, invited professor in University of Illinois, Urbana-Champaign in 1996-1997 and special foreign professor of the University of Tokyo in 2009-2010. He was selected as a PNU Distinguished Professor in 2018. During 35 years at PNU, he has published about 580 refereed journal papers in Domestic and International Journals and supervised 198 MS and Ph.D students. In 2004, he was selected as a member of National Academy of Engineering of Korea.

　　His research interests include: Turbulence, Two-Phase Flows, Flow Visualization, PIV, LIF, PSP, TSP, CFD, Heat Transfer, Thermal System Simulation and Optimization, Next Generation Marine Engine, Organic Rankine Cycle Power System, Multi-scale Multi-physics Analysis and Measurement Techniques, Microfluidics, Bio-MEMS, Lattice Boltzmann Simulation, Solar Power, Cryogenics, Wind Turbine and Fuel Cell, and Wind Engineering.

　　报告内容：

　　In the past decades, heat transfer and flow behavior in porous medium has attracted lots of researchers. Random nature of stochastic foam provides favorable geometrical properties for thermal applications such as large specific surface area and high porosity. However, notwithstanding intensive investigations for the last two decades, hydrodynamic characteristics of stochastic foam are still poorly understood. Current 3-D printing technology supports printing of transparent complex structures. This study investigates hydrodynamic characteristics of a stochastic foam. Using micro-tomography and stereo-lithography, a transparent stochastic foam was printed. Quantitative flow visualization was performed using refractive index matching technique and time-resolved particle image velocimetry. Mixing and turbulence characteristics were discussed. Mechanical mixing and high turbulence in the stochastic foam is beneficial for thermal applications, but large wake area behind the struts cause high pressure drop. On the basis of the results, a new concept of turbulence due to complex geometry can be named as “structure generated turbulence (SGT)”. Geometrical properties of high-porosity open-cell metallic foams possessing extremely high specific surface area and lots of randomly connected path inside the medium body can improve thermal performance of compact heat exchangers, especially in the two-phase bubbly flow. In this study, flow boiling in metal foam inserted channel is experimentally investigated with a focus on the bubbly flow regime. The channel of cross section 5mm by 50mm is used to study the effects of vertical-up flow. R245fa is studied as the operating fluid and heated water loop is used as a heating source. Boiling heat transfer coefficient and pressure drop properties across different types of metallic foam structure are discussed with the effects of the inlet vapor quality and the heat flux. In order to observe the bubble behavior though the metallic porous media, the visualization experiment was performed using a high speed camera. The results presented in this paper may help to understand the interior flow boiling heat transfer mechanism through the metallic porous media.

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　　　　　　　　　　　　　　　　　　　　　　　　2019年2月23日