| Author: | Hu, Xin |
| Title: | Multiscale thermal management for energy saving, comfort wearing and fire safety applications |
| Advisors: | Fei, Bin (SFT) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Department: | School of Fashion and Textiles |
| Pages: | xxiv, 214 pages : color illustrations |
| Language: | English |
| Abstract: | Buildings are major contributors to global energy use, especially in densely populated urban areas with extreme climates. Therefore, innovative strategies targeting energy savings and sustainability are needed to address these global crises. The thesis explores the thermal management concept across multiple scales, from large buildings to individual and finally the combustion process, providing possible solution for energy savings, comfort wearing and fire safety. The thesis begins with exploring concept of radiative cooling on transparent wood substrates for novel building thermal management. Using a purely solution-based sonochemical synthesis method that requires no temperature or vacuum control, a ZnO-coated transparent wood (CTW) composite was fabricated. This composite exhibit high emissivity (~0.91) across infrared wavelengths, making it a strong candidate for radiative cooling applications. The CTW also maintained reasonable luminous transmittance (~66.04% at a film thickness of ~360 nm), ensuring both visual comfort and illumination. The CTW window demonstrated reduced cooling energy consumption of 229 MJ·m-2 and 95 MJ·m-2 annually compared to normal and Low-E glass in Hong Kong, positioning it as a potential replacement for existing glazing materials. Given that radiative cooling is undesirable during colder periods, this thesis further explores the benefits of self-adaptive radiative cooling regulation concept in building thermal management. The emissivity-modulated transparent wood (EMTW) was fabricated by constructing a Fabry-Perot structure consisting of an AgNWs bottom layer, a PMMA spacer, and a W-VO₂ top on TW. The EMTW exhibits an emissivity contrast of 0.44, showing significant energy-saving potential across different climate zones. In addition, positive emissivity contrast was also achieved on three other industrially relevant substrates (e.g., PET, cement, and glass), demonstrating the broad applicability and significance of this approach for promoting radiative cooling regulation in the built environment. Then, the thesis shifts focus to personal thermal management, exploring radiative cooling regulation on textiles. As a proof-of-concept, a prototype of self-adaptive radiative cooling fabric (SARCF) was developed, featuring high solar reflectance and variable infrared emissivity. The SARCF was created by depositing W-VO₂(M) nanoparticles on low-emissivity fabrics, followed by stitching with nanoporous polyethylene (NanoPE). This fabric exhibits significant solar reflectance (85.19%) and a promising emissivity contrast (34.82%) for radiative cooling regulation, driven by the temperature-induced phase transition of VO₂(M). Below the phase transition temperature (Tc) of VO₂(M), SARCF suppresses radiative cooling and reflects body heat with low emissivity (39.38%). Above Tc, the fabric's emissivity increases (74.20%), enhancing radiative cooling. This shift is beneficial for effective personal thermal management across various environments. Indoor and outdoor tests revealed that SARCF outperforms low-emissivity fabrics and white cotton, providing better warming (3°C higher than low-emissivity fabrics) and cooling (4.67°C). Finally, this thesis further extends the thermal management concept downward to the combustion process, aiming to explore the heat control process in combustion. 9,10-Dihydro-10-(2,3-dicarboxypropyl)-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO-ITA) was successfully prepared from 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and itaconic acid (ITA). Then DOPO-ITA was chemically integrated into epoxy chains within a lignin-modified wood framework, the resulting flame retardant transparent wood (FRTW) demonstrated excellent fire safety, with a limiting oxygen index (LOI) of 31.7% and a UL-94 V0 rating. It also enhanced mechanical properties, reaching 94.98 MPa, while maintaining high visual transparency (up to 84.7% at 550 nm). Cone calorimetry revealed that FRTW20 significantly reduced peak heat release rate (HRR), total heat release (THR), and total smoke production (TSP) compared to standard transparent wood. This innovation addresses the critical issue of fire safety in transparent wood, making it a viable glazing material for modern, energy-efficient buildings. In summary, this thesis presents thermal management at various scales, leveraging radiative cooling coating, radiative cooling regulation coating and flame-retardant curing agent to enhance energy efficiency of building, wearing comfort and fire safety of TW, respectively. The research addresses the fire safety of transparent wood, proposes dynamic radiative cooling regulation for transparent wood in various climates, and extends emissivity regulation concepts to fabrics. The demonstrated approach for emissivity regulation holds significant potential for widespread adoption across other established materials. |
| Rights: | All rights reserved |
| Access: | open access |
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