Fundamental study of durability in thin hydrophobic films for dropwise condensation

Enhancement in condensation heat transfer has the potential to increase the energy efficiency of steam power plants by 2% signifying its importance in global energy landscape and environment. Dropwise condensation on thin hydrophobic films where discreet droplets form from steam condensation has the prospective to achieve excellent heat transfer due to continuous shedding of water droplets. However, these thin films (~100 nm) are not durable for continuous dropwise condensation. Understanding the fundamental properties of these thin films is imperative to gaining insight into durability. One of the major properties that define the interface of the coating during steam condensation is interaction of the solid surface with the liquid or water. First, we begin by investigating the interfacial surface energy of thin films with respect to various liquids using a direct meniscus method. The results show our method is as accurate as contact angle method, and high surface energy materials can also be studied giving it an edge over other methods. Then we develop two distinct diagnostic tests for durability :1) Using electrodeposition to visualize pinhole defects and directly compare the density over chosen films, and 2) Using mass transfer process through thin film coatings as a proxy to durability testing in an actual condensation setting. Both these tests are capable of dictating durability within a shorter amount of time compared with current year-long durability tests. Finally, we investigate Dynamic PDMS a class of self-healing vitrimer material as a prospective durable hydrophobic coating for dropwise condensation. Using Atomic Force Microscopy (AFM) we elucidate the mechanism of scratch healing in such self-healing materials. The techniques and insights presented here will inform future works on thin polymeric materials and enable their durable design for plethora of applications including dropwise condensation of steam.

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

2024

Author dc:creator

• Zarin, Ishrat

Contributors dc:contributor

• Miljkovic, Nenad
• Miljkovic , Nenad
• Jacobi, Anthony
• Ferreira, Placid
• Evans , Christopher

• Hydrophobic
• Durability

Statement dc:rights

• Copyright 2024 Ishrat Zarin

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/127172

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F127172