Seminar - Complexity on droplet evaporation by Dr. Fei Duan
Date: 13 December 2013 (Friday)
Time: 3:30 pm - 4:30 pm
Venue: EF305, The Hong Kong Polytechnic University
Evaporation is a process of a liquid changing to its vapor phase. Naturally, it balances the water transport in our environment. Industrially, the important applications are concentrating foods and chemicals, treating sea water, coating, printing, spraying, drying, etc. Although the evaporation process has been investigated for over 200 years, it is still one of the hottest topics at the present stage since the basic mechanism of certain important processes is complicated. A review study shows that liquid evaporation rates, occurring at nominally the same experimental conditions, have been reported by the different investigators to differ by up to 1000%. The variation suggests the complexity in the droplet evaporation. In our single droplet steady state evaporation, the temperature discontinuity was found at the interfacial liquid and vapor sides in an evaporation droplet while the temperature gradient was found along the evaporation interface. The Marangoni flow can be introduced by the interfacial temperature variation. The surface flow can transport and redistribute the energy at the free interface. As a result, the local evaporation is also affected. Taking the complexity into account, we develop the statistical rate theory (SRT) approach to predict the evaporation from liquid phase to vapor phase. The approach introduces the concept of transition probabilities defined in quantum mechanics and the Boltzmann definition of entropy. The theory is managed to predict the evaporation conditions and some thermodynamic properties. On the other hand, the study extends to drying nanofluids droplet. The experiments demonstrate the drying patterns such as finger, coffee ring, uniform coverage and the combined structures. We develop the kinetic Monte Carlo model and the diffusion-limited aggregation model to explain the self-assemble processes.
Dr. Fei Duan joined Nanyang technological University as an assistant professor in 2008. He graduated from University of Toronto in Canada. He also worked as a visiting scientist in Institute of Fluid Mechanics at Friedrich-Alexander-University, Erlangen-Nuremberg, Germany. Now he works on droplet evaporation, nanofluid drying, and thermal cooling, etc. He advised 6 Ph.D. and 5 Master’s students since 2008. Dr. Duan published over 80 journal papers, peer reviewed conference papers and book chapters. He is a member of ASME and ACS.