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2012 年 11 月 28 日
Public Lecture - Microscale Transport Characteristics in Micro-Energy Systems by Prof. Ping Cheng

Date:    28 November 2012  (Wednesday)

Time:    10:30 am -12:00 nn

Venue:   Senate Room, PolyU

Prof. Ping Cheng 鄭平院士

Member of Chinese Academy of Sciences 中國科學院院士

Shanghai Jiaotong University 上海交通大學

Dr. Ping Cheng, elected a member of Chinese Academy of Sciences in 2011, is presently a Chair Professor of School of Mechanical Engineering at Shanghai Jiaotong University. He obtained his B.S. degree in Mechanical Engineering from Oklahoma State University, his M.S. degree in Mechanical Engineering from MIT, and his Ph.D. in Aeronautics and Astronautics from Stanford University. Prior to his present position, he served as Chairman of Mechanical Department at University of Hawaii (1989-1994) and as Head of Mechanical Engineering Department at Hong Kong University of Science and Technology (1995-2002).  Professor Cheng has done seminal research work in porous-media heat transfer with applications to geothermal energy recovery and fuel cells, radiative gasdynamics with applications to re-entry of space vehicles, and most recently in microscale heat transfer with applications to cooling of electronic chips. He has published over 200 SCI journal papers that have been cited more than 5000 times according to Science Citation Index (SCI), achieving an H-factor of 39. A Fellow of American Society of Mechanical Engineers(ASME)and American Institute of Aeronautics and Astronautics (AIAA), Prof. Cheng has received four top international honors, including (i) 2005 ASME/AIChE Max Jakob Memorial Award (considered to be the highest honor in the field of heat transfer), (ii) 1996 ASME Heat Transfer Memorial Award, (iii) 2003 AIAA Thermophysics Award, and (iv) 2006 ASME Heat Transfer Classic Paper Award. He was also a recipient of 2006年上海市科学技术一等奖and 2007 年国家自然科学二等奖. Prof. Cheng is also very active in professional service, serving as Editors for International J. of Heat & Mass Transfer and International Communication on Heat & Mass Transfer. He is also on the editorial boards of 14 other international heat transfer and energy journals. Prof. Cheng is the past Chair of the ASME/AIChE Max Jakob Memorial Award Committee, and he will be the Chair of the 16th International Heat Transfer Conference to be held in Beijing on Aug.10-18, 2018

Seminar Abstract

Advances in micro-fabrication technologies have led to the recent miniaturization of many energy systems such as microchannel heat sinks, micro-evaporators, micro-condensers, micro-fuel cells, and micro-chemical reactors etc. For optimal design of these micro-systems, it is important to understand microscale transport processes occurring in these systems. As the characteristic length of the system becomes smaller, gravitational force is negligible compared with surface tension force, and interfacial effects such as wettability and roughness effects play  major roles in many transport processes. For flow boiling in microchannels, the size effect leads to large-amplitude temperature and pressure oscillations which may result in early burnout. Methods of enhancing nuclear boiling and delaying critical heat flux by modifications of surface wettability and microstructures are discussed. For condensation flow in microchannels, stratified flow no longer appears and intermittent flow becomes the predominant condensation flow pattern. Pore-level simulation results based on the Lattice Boltzmann method, capable of taking microstructures of the carbon paper and local variation of wettability into consideration, show that water flooding problems in PEM fuel cells can be avoided if hydrophilic paths are introduced in the carbon paper gas diffusion layer.