/library/oar/handle/123456789/902 2025-11-04T23:45:32Z 2025-11-04T23:45:32Z Degiorgio, Kevin Muscat, Martin Mollicone, Pierluigi /library/oar/handle/123456789/139105 2025-09-19T07:29:40Z 2025-01-01T00:00:00Z

Title: RCC-MRx type P damage assessment methodologies for the design of nuclear fusion reactor components Authors: Degiorgio, Kevin; Muscat, Martin; Mollicone, Pierluigi Abstract: The RCC-MRx (Design and Construction Rules for mechanical components of nuclear installations: high-temperature, research and fusion reactors) code is developed by the French Association for Design, Construction and Surveillance Rules of Nuclear Power Plant Components (AFCEN). RCC-MRx differentiates between the different type of component damage depending on the type of load set. A constant steady load results in Type P damage while a cyclic time varying load results in Type S damage. The work presented here deals with Type P damages. Two failure modes are of interest: immediate excessive deformation and immediate plastic instability. To prevent these failure modes, RCC-MRx presents an elastic, limit analysis and an elastoplastic approach. The elastic approach is guaranteed to give a safe but highly conservative design. The limit and elastoplastic approach require more computational effort and requires the availability of the relevant material properties. The latter approach leads to less conservative but still safe designs. Having a structurally safe and less conservative design is most of the time preferred because of issues of sustainability and cost. RCC-MRx has primarily been written for fission type nuclear reactors and process pressure vessels rather than for nuclear fusion reactors. Fusion reactors differ from fission ones both in the type of loading and also in the type of geometry. Some fusion reactor components have a box type shape rather than cylindrical or spherical as in fission type reactors and process pressure vessels. RCC-MRx has a section dedicated to the assessment of box type of structures. This paper considers the Type P damage rules for negligible creep and negligible irradiation applied to a simple hollow box section, modelled in cantilever mode under the action of various load sets. The results indicate that elastic analysis is the most conservative. Also, depending on overall deformation of the structure, the results show that the elastoplastic plastic instability rule limit may be reached before that of the elastoplastic excessive deformation rule. The elastoplastic rule for excessive deformation presents several challenges in its application and is discussed in more detail together with a methodology to overcome these difficulties. The finite element software Ansys® Academic Research Mechanical, Release 2023 R2 is used as the analysis tool.

2025-01-01T00:00:00Z Fenton, Daniel Cimarelli, Andrea Mollicone, Jean-Paul van Reeuwijk, Maarten De Angelis, Elisabetta /library/oar/handle/123456789/139024 2025-09-16T08:59:25Z 2024-01-01T00:00:00Z

Title: Countergradient turbulent transport in a plume with a crossflow Authors: Fenton, Daniel; Cimarelli, Andrea; Mollicone, Jean-Paul; van Reeuwijk, Maarten; De Angelis, Elisabetta Abstract: Direct numerical simulation of a turbulent forced buoyant plume in a crossflow is performed at a source Reynolds number , Richardson number , Prandtl number and source-to-crossflow velocity ratio . The instantaneous and temporally averaged flow fields are assessed in detail, providing an overview of the flow dynamics. The velocity, temperature and pressure fields are used together with enstrophy fields to describe qualitatively the evolution of the plume as it is swept downstream by the crossflow, and the mechanisms involved in its evolution are outlined. The plume trajectory is determined quantitatively in a number of ways, and it is shown that the central streamline and the centre of buoyancy of the plume differ significantly—as with jets in crossflow, the central streamline is seen to follow the top of the plume, whereas the centre of buoyancy, by definition, describes the plume as a whole. We then investigate the turbulence properties inside the plume; in particular the eddy viscosity and diffusivity are presented, which are significant parameters in turbulence modelling. Assessment of turbulence production demonstrates the presence of regions where turbulence kinetic energy is redistributed to the kinetic energy of the mean flow, implying a negative eddy viscosity within certain regions of the domain. Similarly, the observation that the buoyancy flux and buoyancy gradient are anti-parallel in specific regions of the flow implies a negative eddy diffusivity in said regions, which must be realised in models of such flows in order to capture the countergradient transport of thermal properties. A characteristic eddy viscosity and diffusivity are presented, and shown to be approximately constant in the fully developed regime, resulting in a constant characteristic turbulent Prandtl number, in turn signifying self-similarity.

2024-01-01T00:00:00Z /library/oar/handle/123456789/138556 2025-09-01T10:22:04Z 2024-01-01T00:00:00Z

Title: Comparative study of monofacial and bifacial solar photovoltaic system performance in the built environment Abstract: Recent advancements in solar photovoltaic (PV) manufacturing technology have witnessed the introduction of bifacial PV modules. The primary distinction lies in their energy generation capabilities, with monofacial modules producing energy solely from the front, while bifacial modules can generate electricity from both the front and back, resulting in higher power output per m². This study aims to analyse typical installation scenarios to determine which technology fits better for the purpose. It investigates whether placing bifacial modules close to the roof, as installers commonly do, is sensible. Furthermore, the contribution of the back surface energy production for different inclinations (15°, 30° and 90°) was assessed. Therefore, this dissertation provides answers to frequently asked questions that are commonly asked by building services engineers, given that all new and renovated buildings will need to achieve net zero-energy status after 2032, according to the forthcoming EU Energy Performance in Buildings Directive. A demonstration setup incorporating both monofacial and bifacial modules was designed and installed to serve as a test bed. Moreover, modelling using Polysun software was applied to further extrapolate the expected yield over a full year, providing valuable insights for conducting a cost-effectiveness analysis for both technologies. Results showed that as the angle of inclination increases, the energy production from the back side of bifacial modules increases, and this contribution becomes more prominent in comparison to frontside energy production on cloudy days, making bifacial modules an ideal candidate for use as sound barriers on arterial roads. Setting bifacial modules at very low angles such as 15° practically defeats the purpose of bi-faciality and this is also true for facade installations. On a micro-scale it was noted that most of the energy generated from the back occurs around solar noon. This means that the inverter needs to be sized accordingly to avoid shaving off the extra energy during peak sunshine hours. If the inverter was undersized, a practice that is widely used for monofacial PV modules, this issue can arise. In comparison, monofacial modules, showed lower overall energy yields under similar conditions, particularly when installed at higher tilt angles. Despite their higher initial costs, bifacial modules demonstrated a superior energy yield and potential for increased cost-effectiveness over time, especially in applications where space constraints and high reflectivity are factors. This highlights the importance of considering bifacial modules for installations where maximizing energy output is critical. Description: M.Sc.(Melit.)

2024-01-01T00:00:00Z /library/oar/handle/123456789/138555 2025-09-01T10:18:45Z 2024-01-01T00:00:00Z

Title: Power quality analysis and improvements within a local hospital Abstract: This master's dissertation investigates power quality (PQ) within a local hospital, aiming to identify, analyse, and mitigate PQ issues that could compromise critical medical equipment and patient safety. Hospitals rely on a stable and reliable power supply to operate essential medical devices and IT systems. Disruptions in PQ, such as voltage sags, spikes, and harmonic distortions, can cause significant operational and safety challenges, including equipment damage and increased maintenance costs. The study begins with a comprehensive PQ assessment using advanced monitoring equipment to collect real-time data on voltage, current, frequency, and harmonics across various hospital departments. Key areas of concern include high-power medical devices like CT scanners, linear accelerators, and chilled water pump sets. The data collected is analysed to pinpoint specific PQ disturbances and their frequencies, magnitudes, and durations. In response to the identified issues, the dissertation proposes targeted mitigation measures, specifically the installation of single-tuned passive filters for the 5th and 7th harmonics. These filters are designed to reduce harmonic distortions and improve overall power quality. The effectiveness of the proposed solutions is evaluated through detailed simulations using MATLAB Simulink, replicating the hospital's electrical distribution system and assessing the impact of the filters. The simulation results indicate that the proposed filters significantly decrease the unwanted harmonics, thereby improving the PQ of the system, enhancing the reliability and safety of the hospital's power supply. The dissertation concludes with recommendations for continuous PQ monitoring and proactive maintenance to prevent future issues, ensuring the hospital can maintain high standards of patient care and operational efficiency. Description: M.Sc.(Melit.)

2024-01-01T00:00:00Z