Structured surface enhanced flow boiling

Flow boiling is prevalant in a variety of industrial sectors such as thermal management of electronics, automotive and off-road vehicles, distillation, chemical synthesis, desalination, thermoelectric power generation, refrigeration, and cryogenics since it offers the dual advantage of near-isothermal operation, and ultra-efficient energy transfer. Although the flow boiling heat transfer coefficient, a characteristic measure of the efficiency of heat transfer, is higher when compared to other modes of thermal exchange such as single phase flow, a vast amount of work has been done in the recent past to further enhance two-phase heat transfer coefficients via surface-structuring techniques. However, the majority of such studies suffer from limitations of being difficult to scale, not being characterized for durability, being difficult to manufacture on typical heat exchanger materials or having typically been studied with water as the working fluid. To address these gaps, this dissertation focuses on development of scalable fabrication methods to enhance effective heat transfer coefficients for metal-based heat exchangers with refrigerants as the working fluid. We begin by fabricating internal micron scale and nanoscale structures on the internal surface of an aluminum tube and demonstrate enhancements in heat transfer coefficients for the microstructured surface. Building on these findings, we extend the microstructuring techniques to copper and stainless-steel to examine surface-structuring enabled heat transfer coefficient enhancements. We then evaluate enhancements on existing enhanced tubes by microstructuring finned aluminum tubes through crystallographic chemical etching and demonstrate improvements in thermal performance. Finally, predictive mechanisms for heat transfer coefficients are examined and an artificial neural network is developed for high-accuracy HTC prediction. The insights presented in this thesis help in potential applicability of the demonstrated microstructuring techniques to full-scale heat exchangers.

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

• Nithin Vinod Upot, -

Contributors dc:contributor

• Miljkovic, Nenad
• Jacobi, Anthony
• Elbel, Stefan
• Banerjee , Arijit

• Boiling
• Structures: Scalable

Statement dc:rights

• Copyright 2022 Nithin Vinod Upot

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/117536

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F117536