Master thesis and internship[BR]- Master's thesis : Performance simulation of a latent heat storage device using the Particle Finite Element Method[BR]- Integration internship

Abstract

The ongoing climate crisis requires the development of sustainable energy solutions. As part of the broader effort to reduce carbon dioxide emissions, this master thesis focuses on the numerical modeling of thermal energy storage systems for residential buildings. Specifically, this work investigates latent heat thermal batteries using phase change materials to store excess solar energy during warmer months and to release it for building heating during winter.

The numerical simulations conducted in this thesis are devoted to the charging phase of thermal energy storage systems. For this purpose, PFEM3D, a particle-based fluid dynamics solver, METAFOR, a finite element code dedicated to solid mechanics simulations, and their coupling through the FSPC coupler are used. These three codes are developed by the MN2L laboratory of the University of Liège.

A major component of this master thesis consists in the optimization of the numerical mesh to get the best compromise between simulation accuracy and computational cost. To achieve this, a temperature gradient-based refinement method with successive improvements was developed. Compared to the temperature-field-based meshes used initially, the optimized mesh led to a substantial reduction in computational time, resulting in a speed-up factor of eight, while maintaining a comparable level of accuracy.

To improve heat transfer efficiency in thermal energy storage systems, this work explores the integration of extended surfaces such as metallic fins. By increasing the contact area, these fins help counteract the inherently low thermal conductivity coefficient of phase change materials. A parametric study on the positioning of a single fin showed that placing the fin at 20-25% of the enclosure height can accelerate the melting process by over 40%, significantly enhancing the battery’s charging efficiency. These findings were validated through comparison with benchmark studies in the literature, confirming the potential of fin-enhanced phase change material systems for heat storage.