Fouling Physics on Soft Materials and the Rational Engineering of Antifouling Heat Transfer Surfaces
Embargo bis 2025-10-15
Autor(in)
Datum
2024Typ
- Doctoral Thesis
ETH Bibliographie
yes
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Abstract
Fresh water and energy are essential resources in our daily lives, interdependent, and
vital for numerous processes. Water is necessary for energy production as a cooling
medium, while energy is needed for effective water treatment and distribution. The
limited availability of these resources, combined with challenges like climate change
and population growth, stresses their interconnection, known as the water-energy
nexus. A key challenge within this nexus is fouling or scaling, which involves the
buildup of unwanted deposits from microscale particles and inverse soluble minerals
like calcium carbonate and calcium sulfate. Fouling impairs water treatment and
energy production, causing energy losses and high costs. Despite previous efforts to
develop materials and strategies to prevent and reduce fouling, the problem persists.
This is partly due to an incomplete understanding of the underlying mechanisms
of fouling, which are crucial for guiding the design of antifouling and scalephobic
materials to improve efficiency and reduce stress within the water-energy nexus.
In this thesis, we aim to counteract this by exploring the complex phenomena of
fouling and establishing a scientific base for its fundamental physics. We develop in
situ measurement techniques to analyze and gain a fundamental understanding of
microscale fouling formation and removal, leading to effective design guidelines for
creating antifouling and scalephobic materials to prevent and minimize fouling.
In the first study, we introduce an advanced in situ measurement methodology
that integrates fluidic and adhesion theories to examine microfoulant adhesion and
removal on compliant engineered surfaces. We analyze the effects of interfacial
hydrodynamics, material compliance, wettability, and surface microtexture on removing
microfoulants such as calcium carbonate and microplastic particles. Unlike
previous ex situ studies, we find that altering the wettability of rigid materials does not impact removal performance, highlighting the importance of in situ studies.
We identify three primary microfoulant removal mechanisms: gliding, rolling, and
shedding, and demonstrate that surface microtexture enhances removal efficiency
through shedding. Our results suggest that antifouling materials should be tailored
to the specific fouling mechanism: rigid coatings are effective for particulate fouling,
while soft coatings are better for crystallization fouling. However, excessive
compliance can hinder removal due to indentation and lubrication-induced gliding.
Based on these insights, we design and successfully test a microtextured compliant
superhydrophilic hydrogel coating with superior scale-shedding properties under
various flow conditions. In outlook experiments, we explore combining the designed
surfaces with noninvasive removal techniques, such as external acoustic
fields, showing promising preliminary results.
The second study investigates in situ the deposition of calcium sulfate scale on
engineered metallic heat transfer surfaces. We develop a continuous flow fouling
unit with microscopic resolution and heat transfer quantification to examine the
effects of material composition and surface structure on scale formation and its
impact on heat transfer resistance under hydrodynamic shear flow. Our in situ
optical characterization and thermofluidic modeling reveal that degassing-induced
bubble formation creates local hot spots and enhances supersaturation, substantially
impacting scaling and heat transfer. We quantify bubble appearance, residence time,
and coverage based on surface composition and structure. These findings suggest
that suppressing surface bubbles is essential to prevent fouling. We, therefore,
designed a nanostructured superhydrophilic scalephobic surface that prevents bubble
formation, reduces scale deposition, and maintains high heat transfer efficiency.
In the third study, we leverage the findings from the first two studies to evaluate
the scalephobic properties of a hydrogel under severe crystallization fouling
conditions in a liquid cooling flow unit. Our initial findings indicate that the soft
hydrogel demonstrates substantially prolonged experimental duration compared to a
rigid substrate before dense intergrown crystal clusters develop. We attribute this
delay to the detachment of individual crystals and crystal clusters, a phenomenon
not previously observed in situ under accelerated severe fouling conditions. The
durability and enhanced cooling efficiency of the scalephobic hydrogel demonstrate
its potential to address fouling to reduce stress on water and energy resources, paving
the way for a sustainable future. Mehr anzeigen
Persistenter Link
https://doi.org/10.3929/ethz-b-000699644Publikationsstatus
publishedExterne Links
Printexemplar via ETH-Bibliothek suchen
Beteiligte
Referent: Schutzius, Thomas Michael
Referent: Terzis, Alexandros
Referent: Ahmed, Daniel
Referent: Style, Robert
Verlag
ETH ZurichThema
Antifouling surfaces; antifouling; Soft materials; Hydrogel; Crystallization fouling; Calcium carbonate; Calcium sulfate; Thermodynamics; Heat transfer; Microstructures; Nanostructures; Shear flow; Water-energy nexus; Surface engineering; scalephobicity; µ-sFDGOrganisationseinheit
09702 - Schutzius, Thomas (ehemalig) / Schutzius, Thomas (former)
Förderung
853257 - De-railing scaling: From fundamentals of crystallization fouling on nano-materials to rational design of scale-phobic surfaces (EC)
Zugehörige Publikationen und Daten
Is supplemented by: https://doi.org/10.3929/ethz-b-000699641
ETH Bibliographie
yes
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