报告题目：How to Promote Drop-Wise Condensation using a Shearing Airflow
报告人：Alidad Amirfazli， York University
Drop-wise condensation is superior to the usual film-wise condensation, but maintaining a drop-wise condensation condition is challenging, and condensate droplets needs to be removed constantly. Applications such as water harvesting from air and life support systems for space exploration involves humid air condensation. To maintain drop-wise condensation one of the following driving forces needs to be used to shed the droplets: gravity, aerodynamic drag force, capillary, or a combination of former forces. Capillary as a driving force has a limited range, and gravity is not available when surface is horizontal, or in specialized applications such as space exploration that has motivated this work. As such, in this talk the focus will be on strategies to promote droplet shedding that are due to a shearing airflow to generate the drag force. The influence of airflow (1 to 15 m/s) on shedding of condensates and resultant heat transfer coefficient for condensation from humid air (10–80% RH) on a horizontal surface (at subcooling temperature of 0–10°C) will be discussed. Three different cases will be considered: (1) a baseline case where surfaces tested are simple, i.e., only the surface coating is changed and there are no other surface features; (2) when electrodes are embedded in the surface; and (3) when there are conical surface decorations present. Given that drop-wise condensation is inherently a cyclical process, so heat transfer coefficient (HTC) needs to be measured as a transient quantity. As such, this talk will also highlight the developed measurement method. Unlike the methods in literature using the steady-state approach, our method is based on a transient inverse heat conduction approach to characterize the time-varying surface heat flux and associated heat transfer coefficient. Finally, results from our microgravity flights that demonstrates the importance of surface wettability on shedding of droplets will be briefly presented.
Alidad Amirfazli is a Professor and Department Chair (Mechanical Engineering) at the York University, and formerly held the Canada Research Chair in Surface Engineering at the University of Alberta. Prof. Amirfazli has conducted exciting work in the area of surface engineering, capillarity, wetting and adhesion, as well as icing and condensation. He has had more than 300 scientific contributions, many in prestigious peer reviewed journals; he has also given many invited talks at international level. He was the Editor for the Advances in Colloid and Interface Science (IF 9.9) for 11 years, and currently is an Associate Editor for the Droplet journal (Wiley); as well as Editorial board member for journals such as Surface Innovations, J Colloid Interface Sci. Open, and Colloids & Surfaces A. Dr. Amirfazli has been the recipient of the Martha Cook Piper Research prize, Petro-Canada Young Innovator Award, and Killam Annual Professorship. In 2014 he was inducted into the Royal Society of Canada’s College of New Scholars, Artists and Scientists. He served as the President of RCS’s College in 2015-16. He has received for an unprecedented number of times, i.e., three times the NSERC Discovery Accelerator Supplement award. He also served in the board of Professional Engineers of Alberta, and been a consultant with various companies in USA, Europe, and Canada. He is a Fellow of EIC and CSME.