Modelling surface effects in two-phase fluid processes across scales

My fellowship aims to develop expertise in the area of boiling and nuclear thermal hydraulics research via the development of novel analytical and computational techniques, the generation of new experimental data and their application to model the behaviour of boiling fluids in industrial systems.

The behaviour of fluids, such as water, used in industrial processes and power generation, is to a large extent governed by the interaction of bubbles and droplets with solid surfaces. These are found in heat exchangers, boilers and condensers and are integral part of the operation of nuclear reactors, which relies on the boiling of water at solid surfaces. Altering the physical and chemical properties of industrial surfaces enables controlling heat and mass transfer in fluid processes such as boiling flows, greatly increasing their potential as coolants. Surface modification could then be used to develop bespoke surfaces to enhance heat transfer in the core and in cooling systems of nuclear reactors. Development of such a technology requires a sound physical understanding of surface effects in fluids through theoretical analysis and numerical modelling. During my fellowship I will develop fundamental modelling techniques to study the surface-dependent behaviour of fluid processes found in nuclear thermal hydraulics applications. The radically new methodologies required to enable this technological inventive step will be developed via collaboration with world leading experts and state-of-the-art facilities found within the Thermofluids, Tribology and Nuclear Engineering Groups of the Mechanical Engineering Department at Imperial College London, enriching the development of computational models of fluid processes with insight from new experiments and simulation at the molecular scale. Collaboration with project partners Rolls-Royce and Hexxcell will ensure direct industrial application of methods and capabilities generated during my fellowship (see the accompanying Project Partner Statements of Support).

In-depth knowledge of the influence of surface effects on nuclear reactor thermal hydraulics is crucial to the operation of the current fleet of water-cooled reactors and is required for the design and safety certification of new' Generation III+' plants planned to be constructed in the UK, as well as for the assessment of future reactor concepts. Some of these, such as the Advanced Modular Reactor, are at the core of scoping studies by the government. The knowledge and capabilities generated by this fellowship will provide the civil service, such as the Department of Energy & Climate Change (DECC), now part of the Department for Business, Energy & Industrial Strategy (BEIS), with a solid scientific foundation for the UK civil nuclear energy policy.

Outside of the nuclear sector, stakeholders will benefit from industrial exploitation of the new, more capable modelling techniques proposed in the course of my fellowship. The work will have wide application to the design of industrial processes that use, for example, boilers, condensers, heat pipes and cooling systems. These are increasingly relying on the use of Computational Fluid Dynamics simulation (CFD) for their design. Developers of CFD software will benefit from the newly developed physical modelling capabilities delivered by my fellowship and will be able to implement the new simulation approaches into their commercial software packages.

My fellowship will deliver radically new modelling techniques and prime experimental data that will benefit the community of scientists and engineers working with heat and mass transfer processes in two-phase flows and will enable unprecedented understanding of the physical mechanisms of interaction between solid surfaces and two-phase flows. These processes are integral part of power generation, propulsion, heating and cooling, and more generally of any energy conversion system. Impact of the proposed research will materialise as an ability to drive the above applications harder and to quantify rigorously their safety limits, contributing to their de-carbonization and to the reduction of their environmental impact, thus improving their public acceptance.

My fellowship research plan has been laid out in order to maximise impact on the nuclear sector. The modelling techniques developed, the experimental data collected, and the new understanding of physical phenomena gained during this fellowship will benefit designers of nuclear reactors, the Office for Nuclear Regulation (ONR) and UK policy makers and civil servants of the Department of Energy & Climate Change (DECC), now part of the Department for Business, Energy & Industrial Strategy (BEIS). Increased confidence in the understanding of the basic physical processes will benefit regulators responsible for the safety assessment of reactor concepts. From a societal point of view, knowledge and capabilities so developed will be made available for policy makers to promote nuclear power in its role as an indispensable component of the UK provision of electricity from various sources. Demonstration of new simulation methodologies will benefit developers of Computational Fluid Dynamics (CFD) software used for nuclear reactor thermal hydraulic analyses. Thanks to better modelling capabilities, a sound physical understanding will be developed of critical thermal hydraulic parameters influenced by surface effects. Newly acquired knowledge and capabilities will be available for designers of nuclear systems to improve the efficiency and safety of plants. This will enable more rigorous evaluations of safety margins and limit conservatism in reactor thermal design.

From an economic point of view, close collaboration with industrial partners Rolls-Royce and Hexxcell (see the accompanying Project Partner Statements of Support) will streamline the process of knowledge transfer to the engineering of vital heat transfer equipment used in power plants.

Impact on the operation (and, in the UK, construction) of current 'Generation III+' reactors is expected in a time scale comparable to the three years of duration of this fellowship. Future UK plans for the development of nuclear power, which are currently considering candidate reactor designs such as the Advanced Modular Reactor, are expected to benefit from the proposed research over a longer time scale, of perhaps 10-20 years.

Outside the nuclear sector, the newly-generated improved methodologies and prime experimental data will benefit scientists and engineers developing two-phase processes with heat and mass transfer, such as boiling and condensation, which are, as noted, integral part of a variety of propulsion, cooling and more generally energy conversion systems. Data and insight on critical surface-related parameters will therefore benefit the thermal hydraulic design and characterisation of the above industrial processes. CFD analysis has become an indispensable step of the design and characterisation protocols employed by engineers developing the above systems. In this context, impact of this fellowship on the developers of CFD software will materialise via the implementation of original physical modelling techniques, initiated during execution of the proposed research, by the developers into their own proprietary software, which will be made available to their academic partners and industrial customers.