Abstract: A lot of the previous studies on boiling heat transfer have been reported since 1950s. They have investigated the typical researches on the theoretical analyses and the experimental approaches on the prediction and the evaluation of boiling phenomena. Since 1990s, according to the wide spreading of MEMS technology, surface manipulation technique has been widely applied to enhance boiling heat transfer performance. Based on the application of MEMS fabrication technology, it could be also feasible to manipulate surface chemical properties resulting in surface wettability control. Moreover, the previous approaches based on microscale surface treatment have been advanced into the application of nanotechnology, which deals with more minute surface morphology. As nanotechnology became to be widely used in industrial fields and academic researches, nanoscale surface treatments even on boiling heat transfer has been identified based on various experimental approaches. In this lecture, the micro-nanoscale surface manipulation techniquesfor the enhancement of boiling heat transfer performance are summarized. First, surface manipulation via silicon nanowire arrays (SiNWs) is conducted as an effective method to increase surface roughness extremely and create natively formed vapor bubble seeds, which are favorable to boiling heat transfer, with microscale dimensions by coalescence of SiNWs. Second, the enhancement of boiling performance is verified using micro-nano hybrid structure fabrication. In details, multiscale structure, which consists of SiNWs and microscale patterns, is introduced accompanying wicking phenomena by nanoscale structure and surface area increase and bubble seeds formation by microscale structure. Then pool boiling performance is experimentally verified in terms of the geometric parameters related to the designing of multiscale structures. Finally, it is demonstrated that the application of optimal multiscale structure considering the boiling characteristics can enhance boiling performance compared with results on a bare surface and previously reported onesvia artificial structures.

Brief Biography of the Speaker:
HyungHee Cho received the B.S. and M.S. degrees in mechanical engineering from Seoul National University, Seoul, Korea, in 1982 and 1985, respectively, and Ph.D. degree in mechanical engineering from University of Minnesota, Minneapolis, MN in 1992. From 1992 to 1995, he was research associate in University of Minnesota. In 1994, he joined Minnesota Supercomputer Institute as a research associate. In 1995, he joined the Department of Mechanical Engineering, Yonsei University, Seoul, Korea, where he is currently a full professor in the School of Mechanical Engineering. From 2003 to 2005, he was the Chairman of Department of Mechanical Engineering at Yonsei University. From 2005 to 2007, he held position as the Associate Dean of College of Engineering at Yonsei University. He is currently the director of The Low Observable Technology Research Center.
His research interests include heat transfer and flow control/designin macro-scale devices as well as micro/nano-scale components.For macro-scale devices, he has been working on heat transfer in turbomachineries, rockets/ramjets and nuclear reactors. Especially, with intensive research on various cooling techniques such as film cooling, internal passage cooling, and impingement/effusion cooling, he has accomplished major research achievements including numerous papers and patents. For nuclear reactors, he has been working on flow-induced vibration and boiling heat transfer enhancement by controlling flow characteristics and heat transfer.For micro/nano-scale components, he has worked on thermal transport phenomena in low dimensional materials as well as thermal management in electronics and semiconductor devices. Recently, he has been working on boiling heat transfer enhancement using nano and micro technology.
He is a recipient of numerous awards such as KSME Scientific Achievement Award (2000), Yonsei Academic Achievement Award (2001), KSFTS best paper award (2006) and KFMA Scientific Achievement Award (2008). Dr. Cho is a Fellow of the American Society of Mechanical Engineers, a Scientific Council Member of the International Centre for Heat and Mass Transfer (ICHMT), and an Associate Member of the Korea Academy of Science and Technology (KMST). He is also a committee member of ASME K-14 (Heat Transfer in Gas Turbine) Committee and vice president of KSME Energy and Power Division. He serves on the editorial board of JP Journal of Heat and Mass Transfer, Advances in Mechanical Engineering, and International Journal of Fluid Machinery and Systems.