The Department of Mechanical Engineering – Engineering Mechanics Graduate Seminar; Thursday, Dec. 12, 2013, 4:00 – 5:00 p.m. Room 112, ME-EM Bldg.,
Mr. D. H. Shin, Mechanical Engineering, Chung-Ang University
Title: Wettability Changes and Fringe Patterns of Contact Lines due to the
Local Aggregation Effect on Nanofluids Droplets during Evaporation
Recently, nanofluids (NF) are of substantial interest because of their potential in exhibiting improved thermal performance. The potential of nanofluids as the next generation of cooling fluids for automobiles and electronic devices has recently led to increased research. Mr. Shin’s research is currently focusing on characterization of nanofluid droplet evaporation by using an image visualization technique of the confocal microscope system.
This presentation will introduce a recent work regarding the nanofluid droplet
evaporation: Evaporation characteristics of nanofluid droplets with various volume fractions of 50 nm alumina (Al2O3) particles are experimentally examined. The effect of particle concentrations on droplet evaporation rates is examined and the corresponding wettability changes and the total evaporation time are also examined. Next, the contact lines of nanofluids droplets during evaporation are visualized using a slit-confocal microscopy, which allows a high-speed reflected mode. As the volume fraction of nanofluids increases, the total evaporation time and the initial contact angles decreases, while the droplet perimeters increase. In order to figure out the cause of results, the triple line of the droplet is visualized to study the wetting dynamics at the initial state using a digital image analysis technique. Conclusively, nanofluids droplets have a shorter total evaporation time than DI-water droplets do. It is observed that the nanofluid droplets are the more hydrophilic on the same kind of surfaces. Those results show the feasibility of using fringe patterns of contact lines can provide instability of a contact-line region in the thin film and further explain heat and mass transfer in this region.
Mr. Dong Hwan (DH) Shin is a visiting research scholar of Mechanical Engineering-Engineering Mechanics at Michigan Technological University. He received his B.S. and M.S. in Mechanical Engineering in Chung-Ang University (CAU) in 2008 and 2010, respectively. He continues his PhD candidate in CAU, Seoul, Korea. He has already been to MTU as a visiting scholar twice in 2010 and 2012. His research interests are nanofluid and its application, evaporation of micro-droplet and its application, flame spray and its application, and computational fluid dynamics. He has published 13 journal papers and 22 proceedings.