Seminar on Origin and Evolution of a Vapor Bubble in Pool Boiling using Experiments and Molecular Simulations

Boiling is amongst the most efficient heat transfer mechanisms and widely used in industry, from cooling small electronics to large power plants. Despite decades of research in pool boiling, the origin of a vapor bubble is vaguely understood. Further, the microlayer, present at the bubble base, is a multi-scale (nano to micro) thin liquid film which dictates bubble evolution. It implicitly and dynamically captures the surface and liquid conditions, and in-turn governs the macroscopic boiling behavior.
 
In order to understand these fundamentals, we performed in situ visualization of a single bubble nucleation in pool boiling. A steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water was created using a laser source. Contrary to current understanding, bubbles originate on hydrophilic and silane-coated hydrophobic surfaces without a three-phase contact line, i.e., the microlayer completely covers the bubble base. The occurrence of such a wetted bubble base is found to be dependent on the liquid-solid interaction. As the bubble grows in time, the film decreases in thickness, eventually forming the contact line and dry region. We also conducted molecular simulations to study the origin of a vapor bubble and compared the nucleation conditions with theoretical model. Such simulations provide new insight into the local conditions occurring in a bubble during the nucleation process. 

Dr. Maroo is an Associate Professor in Mechanical & Aerospace Engineering at Syracuse University. He received his B.Tech from IIT Bombay in 2003, and MS and PhD from University of Florida in 2005 and 2009, respectively. He was a postdoctoral researcher at MIT from 2010-2011. His research interests are in multi-scale transport phenomenon, thermal management, and bio-mechanical systems with a focus on energy and water desalination. Dr. Maroo is the recipient of 2015 NSF CAREER award, and the 2009 best PhD dissertation award in ‘Thermal-Fluid Sciences’ at University of Florida. He has published in journals such as Journal of Physical Chemistry Letters, Scientific Reports, Langmuir, Applied Physics Letters, and Nano Letters, and has received funding from NSF, ONR and DoE.​