Study on Leidenfrost Effect Inhabitation and Pool Boiling Heat Transfer of Structural Thermal Armour

Abstract

This thesis presents a comprehensive investigation into the inhibition of the Leidenfrost effect and the enhancement of pool boiling heat transfer using Structural Thermal Armour (STA), a novel heterogeneous surface architecture designed to overcome the fundamental limitations of conventional thermal management under extreme conditions. Building upon our prior development of STA, which integrates thermally conductive metallic micropillars with a hydrophilic, heat insulating porous membrane and engineered U-shaped vapor venting channels, this work systematically elucidates the underlying multiphase transport mechanisms through integrated high-fidelity numerical simulations and controlled pool boiling experiments.

A multiphysics computational framework coupling the Volume of Fluid (VOF) method with the Lee phase-change model is established to resolve transient vapor-layer dynamics and interfacial heat transfer at unprecedented spatiotemporal resolution. Simulations reveal that the low thermal conductivity of the porous membrane effectively delays localized overheating, while its high surface energy promotes rapid liquid spreading and capillary-driven replenishment, thereby preventing the formation of a continuous insulating vapor film and completely suppresses the Leidenfrost effect up to 1000 °C.. Crucially, the simulations visualize for the first time the sub-membrane vapor transport pathways, confirming that the elevated membrane placement in STA enables spatial decoupling of liquid supply and vapor expulsion—a mechanism fundamentally absent in conventional designs.

Pool boiling experiments validated the hypothesis that STA's high Leidenfrost point on the Nukiyama curve corresponds to high critical heat flux performance. The STA achieves a critical heat flux (CHF) of 611 W·cm⁻², which is more than six times that of a plain copper surface. Systematic parametric studies reveal the synergistic interplay between geometric parameters, achieving a balance between two conflicting design requirements: minimizing energy dissipation for vapor escape and optimizing micropillar height for maximum heat transfer.

Based on experimental and numerical insights, a unified heat transfer model is developed, establishing a direct correlation between interfacial free energy evolution and thermal performance. This model provides a theoretical foundation for the rational design and optimization of STA architectures. The demonstrated capabilities in sustaining nucleate boiling under extreme heat fluxes, maintaining temperature uniformity, and ensuring system reliability position STA as a transformative solution for thermal management in next-generation high-power systems, including advanced nuclear reactors, hypersonic vehicles, and ultra-high-power-density electronics.

Date of Award	19 May 2026
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Jiyun ZHAO (Supervisor) & Zuankai Wang (External Co-Supervisor)