University of Illinois Urbana-Champaign

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

Fazle Rabbi, Kazi

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

Description

Title
Surface micro/nano structuring and functionalization for phase change heat transfer enhancement
Author(s)
Fazle Rabbi, Kazi
Issue Date
2022-04-18
Director of Research (if dissertation) or Advisor (if thesis)
Miljkovic, Nenad
Doctoral Committee Chair(s)
Miljkovic, Nenad
Committee Member(s)
  • Ferreira, Placid Matthew
  • Alleyne, Marianne
  • Wang, Sophie
Department of Study
Mechanical Sci & Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • wettability
  • condensation
  • frosting
  • refrigerant
  • dropwise condensation
  • nanostructure
  • microstructure
  • low surface tension liquid
  • heat transfer
  • jumping droplet
  • superhydrophobic
  • omniphobic
  • liquid repellant
  • refrigeration
  • metal additive manufacturing
Abstract
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.
Graduation Semester
2022-05
Type of Resource
Thesis
Copyright and License Information
© 2022 Kazi Fazle Rabbi

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