Surface micro/nano structuring and functionalization for phase change heat transfer enhancement

Recent advancements in surface nanostructuring have spurred intense interests in their potential for enhanced phase change heat transfer. In this dissertation, novel scalable surface modification methods have been investigated in an attempt to enhance surface condensation performance of conventional and additively manufactured metals. These surfaces: enable jumping droplet condensation in harsh conditions, delay condensation frosting, and enable dropwise condensation of low surface tension liquids. First, a class of tunable micro/nanostructures have been developed on metal additively manufactured AM (AlSi10Mg) surfaces. Optimization of AM nanostructures is shown to achieve better performance when compared to existing nano-structuring techniques on conventional (i.e., aluminum Al-6061) alloys. In addition, experimental results have been presented showing that the AM (AlSi10Mg) alloy having a two-tier nanostructured surface can sustain stable droplet self-repellency via coalescence-induced droplet jumping at high supersaturation (S ≈ 1.8). The condensation performance results in a 600% and 200% enhancement in condensation heat transfer coefficient when compared to filmwise and dropwise condensation, respectively, on nanostructured conventionally manufactured aluminum alloy surfaces. Furthermore, the effect of surface wettability (superhydrophobic, superhydrophilic, and hydrophilic) on condensation frosting delay has been investigated using heat exchanger fins by studying the frost growth rate and how it is affected by different fin pitch, fin surface temperatures and ambient relative humidity. Finally, by combining low hysteresis polymers with a low surface energy coating, a novel omniphobic, substrate independent, solid surface coating has been developed, which can promote the dropwise condensation of low surface tension liquids, including ethanol, hexane, pentane, and a low global warming potential refrigerant.

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

2022

Author dc:creator

• Fazle Rabbi, Kazi

Contributors dc:contributor

• Miljkovic, Nenad
• Ferreira, Placid Matthew
• Alleyne, Marianne
• Wang, Sophie

• wettability
• condensation
• frosting
• refrigerant
• dropwise condensation
• nanostructure
• microstructure
• low surface tension liquid
• heat transfer
• jumping droplet
• superhydrophobic
• omniphobic
• liquid repellant
• refrigeration
• metal additive manufacturing

Statement dc:rights

• © 2022 Kazi Fazle Rabbi

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/115761

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F115761