Multiscale modelling of boiling heat transfer

: from stochastic nucleation to device prediction

Abstract

The relentless advancement of modern technology has led to a substantial increase in thermal loads, posing significant challenges for efficient heat dissipation. Traditional single-phase cooling systems are increasingly inadequate, particularly under high heat flux conditions. Consequently, phase-change cooling techniques, especially boiling heat transfer, have garnered considerable attention due to their superior heat transfer capabilities. Accurately modelling these complex phase-change processes, which involve a coupled interplay of fluid flow, heat transfer, mass transfer, and interfacial surface tension effects, demands advanced computational approaches beyond conventional single-phase methods.
This thesis addresses the critical need for robust computational modelling of boiling phenomena through the development and enhancement of Volume of Fluid (VOF)-based techniques within the OpenFOAM framework. While the VOF method is well-suited for macro-scale simulations of liquid-vapour interfaces, such as bubble growth and detachment, it traditionally struggles to resolve phenomena at smaller, mesoscale levels. To overcome this limitation and enable a multi-scale modelling approach, this work introduces an improved VOF formulation capable of operating effectively at sub-micron spatial resolutions. Through simulations of canonical cases, including single bubble growth and detachment in superheated liquid domains and saturated pool boiling conditions, the enhanced VOF approach demonstrates high fidelity in capturing critical interfacial dynamics, narrowing the gap between continuum-level and mesoscale simulations.
In parallel, a novel stochastic bubble nucleation model is developed and integrated into the VOF framework for application in micro-channel boiling simulations. This model randomly selects potential nucleation sites along heated boundaries and initiates vapour generation when local temperatures exceed the activation threshold determined by the critical radius of nucleation seeds. To further extend its applicability and scalability, the nucleation model has been embedded within a High-Performance-Computing (HPC) framework that enables seamless deployment across arbitrary geometries and supports domain decomposition strategies. This flexible implementation ensures that the model can be efficiently parallelized and utilized in large-scale simulations, making it suitable for complex geometries and processor-intensive applications.
These combined advancements contribute towards the formulation of a unified multi-scale computational strategy for phase-change heat transfer. This framework holds significant promise for the design, optimization, and performance prediction of next-generation thermal management systems, spanning applications from microelectronic cooling and high-performance computing to renewable energy systems. The findings of this work underscore the importance of integrating physical realism with computational efficiency to meet the growing demand for sustainable and effective thermal control solutions.

Date of Award	Jun 2026
Original language	English
Awarding Institution	University of Brighton
Supervisor	Anastasios Georgoulas (Supervisor), Nicolas Miche (Supervisor) & Marco Marengo (Supervisor)