Droplet evaporation dynamics on surfaces

Droplet evaporation governs many man-made and natural processes. Hence, it has been widely studied by many scientists over the past century. With the recent advancements in nanotechnology, many surfaces for two phase heat transfer have been developed including hydrophobic, biphilic and lubricantinfused surfaces. However, evaporation of droplets on these surfaces have not been explored in depth. Traditionally, evaporation on surfaces was characterized by observing the temporal size changes of a droplet. Yet, the transient nature coupled with the significant mass transfer governed gas dynamics occurring at the droplet three-phase contact line make the classical method crude. To accurately investigate evaporation dynamics on surfaces, we present a novel steady measurement technique. By utilizing a piezoelectric dispenser to feed microscale droplets (20 ≤ 𝑅 ≤ 400 μm) to a larger evaporating droplet at a prescribed frequency, we can create variable-sized droplets on any surface and study their evaporation rates by modulating the droplet addition frequency. Using our steady method, we studied evaporation of water and low surface tension fluids on surfaces including functional, biphilic, biconductive and lubricant-infused surfaces. We elucidated the physics governing the droplet evaporation process for each studied surface and working fluid. Furthermore, we developed an original high-speed focal-shift imaging technique to study droplet mobility on the interface. Our results not only shed light into the evaporation physics of droplets on different surfaces but also provides new avenues and strong experimental platforms for the study of phase change heat transfer processes that enable the decoupling of the intricate and length-scale dependent balance played by internal and external flows and binary-mixture dynamics, and the visualization of the interfacial dynamics.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2019

Author dc:creator

• Gunay, Ahmet Alperen

Contributors dc:contributor

• Miljkovic, Nenad
• Jacobi, Anthony
• Brewster, Quinn
• Pilawa-Podgurski, Robert

• Droplet, Evaporation, Phase Change, Surface

Statement dc:rights

• Copyright 2019 Ahmet Gunay

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/105189

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/105189