Improved CFD wall-boiling modelling to better account for heat transfer surface characteristics on the critical heat flux in nuclear pressurized water reactors.

The project will advance the accuracy of Computational Fluid Dynamics (CFD) models employed for predicting boiling heat transfer and particularly the Critical Heat Flux (CHF) in nuclear Pressurized Water Reactors (PWR).

PWR cores are water-cooled and operate at conditions where boiling may occur due to the high surface heat fluxes from the nuclear fuel to the cooling water. All PWRs must therefore control boiling to operate safely. In boiling, the CHF identifies the highest reachable heat flux before a large drop in heat transfer efficiency, due to the heating surface becoming blanketed with vapour, triggers an abrupt overheating of the surface. CHF is a major safety limit for PWRs and reactors must be designed in such a way that CHF is never exceeded to avoid overheating and damage to the fuel clad, the nuclear fuel, and the release of radioactive material. At present, limitations in the modelling and computational approaches used to predict CHF force reactor vendors to introduce large safety margins in their design, i.e., PWRs are operated only at around 75% of the predicted CHF limit, which hinders their economic viability.

In this project, you will develop three-dimensional component-scale CFD approaches capable of predicting boiling and CHF in PWR-relevant conditions. Combining improved physical modelling with the potential of machine learning and data assimilation techniques, you will specifically target two areas where existing models have major limitations:

–       the impact and modelling of real-world boiling surface characteristics. Bubbles nucleate at microscopic cavities, present and non-homogeneously distributed on every heat transfer surface along with different surface defects. These features have a strong impact on boiling conditions but are mostly overlooked in available CFD models. Ideal, homogeneous surface conditions are assumed in models, which can lead to a loss of accuracy when applied to real reactor surfaces;

–       the CFD modelling of CHF that currently does not account for the critical role of the boiling surface microscale characteristics and wettability properties.

By making available CFD predictions of improved accuracy and reduce uncertainty, your research will have transformative impact on the safety, efficiency and economics of PWRs by enabling:

–       PWRs to be designed and substantiated to be safely operated at higher power levels, making them more efficient and sustainable.

–       boiling conditions and CHF margin to be monitored and characterized over the entire lifetime of the nuclear fuel in reactor operating conditions, accounting for the presence of surface defects, ageing effects and deposition of corrosion products.

–       easier and faster assessment of surface finishes and coatings, facilitating the development of safer accident tolerant fuels with a higher margin over melting and the optimization of engineered surfaces with improved heat transfer properties.

You will join the Thermofluids group in the School of Mechanical, Aerospace and Civil Engineering at the University of Sheffield, where you will develop your research and professional skills alongside multiple researchers focused on CFD and boiling modelling. Confident and reliable estimation of the CHF limit are of utmost interest for the nuclear industry and nuclear reactor developers. For this reason, the project is supported by Rolls-Royce. You will continuously interact with Rolls-Royce engineers and have the opportunity to undertake an internship at the company during the PhD. Regular interactions are also expected with PhDs focusing on boiling modelling with CFD at the University of Manchester and supervised by Dr Giovanni Giustini.

Eligibility:

Applicants should have a minimum of an upper second class honours degree in a relevant science or engineering subject such as Mechanical Engineering, Aerospace Engineering, Physics or Applied Mathematics.

How to apply:

Please complete the enquiry form to express your interest – : https://tinyurl.com/2cxa9smw

We strongly recommend you contact the project supervisor after completing the form to speak to them about your suitability and interest for the project: [email protected]

If your qualifications meet our standard entry requirements, the CDT Admissions Team will send your enquiry form and CV to the named project supervisor. 

Our application process can also be found on our website: Apply nearmejobs.eu EPSRC Centre for Doctoral Training in Skills And Training Underpinning a Renaissance in Nuclear (SATURN)

If you have any questions, please contact [email protected] 

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