Scalable fabrication and characterization techniques of nano-engineered stainless-steel surfaces for boiling heat transfer

Ahmed, Asif

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https://hdl.handle.net/2142/129774 Copy

Description

Title

Scalable fabrication and characterization techniques of nano-engineered stainless-steel surfaces for boiling heat transfer

Author(s)

Ahmed, Asif

Issue Date

2025-05-06

Director of Research (if dissertation) or Advisor (if thesis)

Miljkovic, Nenad

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Etching
• nanostructures
• cavities
• heat exchanger surface
• pool boiling
• bubble nucleation

Abstract

Stainless steel (SS) is commonly used in HVAC industry especially in heat exchangers because of high corrosion resistance and durability. In recent times, surface nano-engineering has become a popular way to achieve micro/ nano structured surfaces for boiling applications, as nano-structured surface exhibits higher roughness and increase surface area that ultimately leads to heat transfer coefficient (HTC) enhancement. In the past studies, researchers mainly focused on two other common materials- aluminum and copper, hierarchical surface development using different approaches. However, there’s hardly any literatures available that dealt with chemical etching of SS. In this thesis, a few novel chemical etching recipes have been introduced which is scalable, cost-effective and easy to apply on SS with effective surface roughness outcome and increased nucleation sites. This work represents a novel and scalable fabrication method of hierarchical network of micro- and nanoscale structures on SS304 surfaces by chemical etching and subsequent surface characterization via SEM, FIB, Confocal 3D microscopy, XPS, XRD and contact angle measurement. The maximum roughness was achieved 10μm after etching. In addition to surface characterization, pool boiling heat transfer performance was studied where the etched SS surface demonstrates a two-times increase in critical heat flux (CHF) at reduced superheat, primarily due to increased nucleation activity within optimally sized cavities formed during etching which underscores the potential for developing compact and efficient thermal systems. Additionally, brazed plate heat exchanger (BPHX) made of SS304 plates was etched using FeCl3 solutions and the post-etched micro-structured HX surface enabled up to 30% condensation HTC enhancement. It is evident that, nanostructures and cavities generated by chemical etching plays a vital role in improving boiling performance in heat exchangers.

Graduation Semester

2025-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129774

Copyright and License Information

Copyright 2025 Asif Ahmed

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