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航空学院青年学术论坛第六十四讲
2017-05-14 07:22  

报告人:Professor Kyung Chun Kim, School of Mechanical Engineering, Pusan National University

题目:Flow and heat transfer measurement using thermographic phosphor particles

报告时间:2017519 星期五 下午 2:30-3:30

报告地点:友谊校区航空楼 A706

报告摘要: Quantitative visualization techniques for multi-physics (e.g. simultaneous measurement of velocity and concentration fields) in micro and macro scale flows are addressed in this lecture. Oxygen sensitive particles (OSPs) are developed to measure velocity and dissolved oxygen (DO) concentration fields in microscale water flows. The functional particles are fabricated by a dispersion polymerization method using an oxygen quenchable luminophore (PtOEP) doped PS polymer. A pulsed UV light-emitting diode (UV-LED) illumination system is developed to measure the DO concentration of the particles and the μ-PIV method is used for velocity field measurement. An intensity-based method adopting a modified pixel-to-pixel in situ calibration technique is used to quantify DO concentration fields in a Y-shaped micro channel. The diffusion process of DO through the interface between two parallel water flows having different DO concentrations was quantitatively measured with velocity field in the microchannel.The photo bleaching characteristics of oxygen sensitive particles (OSP) was examined using a high speed imaging technique. The OSPs were fabricated by a dispersion polymerization method and dipping method using porous micro spheres. Two representative oxygen indicator moleculesplatinum octaethyl porphyrin (PtOEP) and platinum (II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP), were used to make four kinds of OSPs. A ultraviolet-light emitting diode (UV-LED, M385L2, THORLABs) with a wavelength of 383 nm, a microscope with a 20X objective lens and a high speed camera were adopted for the high speed imaging of OSPs. The photo beaching characteristics of the OSPs were compared according to the time and power of UV-LED. The dispersion-polymerized OSP had higher photostability than the porous OSP, and the PtTFPP-embedded porous OSP was more stable than the PtOEP-embedded porous OSP due to the molecular structural characteristics. The dispersion-polymerized OSP incorporated with PtOEP was more stable than the dispersion-polymerized OSP incorporated with PtTFPP.

Thermographic phosphors have been used to measure temperature since the late 1930s, and they have been applied to a range of application fields. An inexpensive and simple measurement system was suggested to measure the temperature field and velocity field at high temperature using thermographic phosphor tracer particles. The manganese-activated magnesium fluorogermanate (Mg4FGe6:Mn, MFG) was used as a tracer particle for particle image velocimetry (PIV). A 385 nm UV-LED and only one high speed camera with CMOS sensor were used for the simultaneous measurement system. To validate the constructed simultaneous measurement system, dispersion of the confined oil jet with high temperature was investigated. The instantaneous temperature and velocity field were obtained when 200 ̊C of silicon oil was injected into the 25 ̊C of the silicon oil chamber. For the temperature field analysis, the decay-slope method was used, and the velocity field was obtained by two-frame cross correlation algorithm. The velocity of injected silicon oil was rapidly decreased because of the change of viscosity of silicon oil over temperature. The injected high temperature silicon oil was cooled by surrounding low temperature silicon oil. Therefore, the velocity of oil jet was decreased rapidly and was dispersed widely. The temperature difference before and after of the dispersion point appears significantly, since the temperature of silicon oil difference between the spread widely area and non-spread area. The temperature field and velocity field were obtained successfully by simple simultaneous measurement system using thermographic phosphor tracer.

The transient heat transfer characteristics of a hot plate cooled by an oblique jet were investigated by thermographic phosphor thermometry. The initial surface temperature was 360°C, and 2D instantaneous temperature fields were measured with 0.1-second time intervals for a jet Reynolds number of 3,500. The distance from the nozzle to the surface and the angle of impingement were varied for measurements. Manganese-activated magnesium fluorogermanate(Mg4FGeO6:Mn) was used as a thermographic phosphor, and a pulsed UV-LED with a 385-nm wavelength was used for the light source. A CMOS high-speed camera acquired phosphorescence images at 4,000 frames per second. The decay-slope method was used for calibration, and the uncertainty in the temperature measurement was less than ±3% for the wide temperature range of 130 to 530°C. A 1D semi-infinite solid model was used to obtain the local heat transfer coefficient. The transient heat transfer is almost two times greater than the steady-state value. The maximum heat transfer coefficient occurred at the stagnation point, and a secondary peak appeared at high impinging angle. When the distance from the nozzle to plate is fixed, the air jet with high impinging angle shows better cooling performance. Flow visualization and time-resolved PIV measurements reveal that the secondary heat transfer peak is associated with unsteady vortex at the beginning of the wall jet.

报告人简介: KCKim received his BA degree at the department of mechanical engineering in Pusan National University in 1979. He received MS and Ph.D degree at the department mechanical engineering of KAIST (Korea Advanced Institute of Science and Technology), Korea in 1981 and 1987 respectively. Since 1983, he was hired as a faculty member in Pusan National University (PNU), Korea. He was invited as a visiting professor from Ottawa University in Canada for 1989-1990. He joined at the department of theoretical and applied mechanics in University of Illinois, Urbana-Champaign, USA as an invited professor for 1996-1997. He was invited as a special foreign professor from the University of Tokyo, Japan for 2009-2010.

   During 34 years at PNU, he has published about 560 refereed journal papers in Korean and International Journals and supervised 195 MS and Ph.D students. On the basis of his research outcomes, he received the outstanding paper awards (1995, 2002) from KSME and KOSEF. In 2009 and2016, he received the Academic award and the first Yeosong award from Korean Society of Mechanical Engineers (KSME). He received Nakayama award in 2012 and Asanuma award in 2014 based on contributions in world Visualization society. He is currently serving as an Editor in Chief for Journal of Visualization and Journal of Flow Visualization and Image Processing. He is the chairman of National Congress of Fluids Engineering in Korea since 2015.

In 2002, his laboratory has designated as a National Research laboratory from the Ministry of Science and Education of Korea. Prof. Kim established the MEMS/NANO Fabrication Center and served as the director from 2004-2009. In 2004, he was selected as a member of National Academy of Engineering of Korea. For 2008-2009, He was in charge of the president of Korean Society of Visualization. He was the Chairman of the 14th International Symposium on Flow Visualization which was held in Daegu, Korea, 2010.He is the Chairman of the 12th International Symposium on Particle Image Velocimetry which will be held for June 18-22, 2017, Busan, Korea.

His research interests include: Turbulence, Two-Phase Flows, Flow Visualization, PIV, LIF, 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, Wind Turbine and Fuel Cell.

 

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