Packing, Flow and Heat Transfer of Non-Spherical Particles for Concentrated Solar Power Applications

Abstract

The demand for efficient and cost-effective thermal energy storage systems has intensified with the rapid expansion of renewable energy technologies, particularly concentrated solar power (CSP). In CSP systems, both packed beds utilized in thermal energy storage units and moving beds employed in moving bed heat exchangers are critical components that rely on granular solid materials for heat storage and transfer. Among these materials, bauxite has emerged as a promising candidate due to its thermal stability, abundance, and cost-effectiveness. The overall performance of packed and moving bed systems is strongly influenced by the flowability, packing structure, and heat transfer characteristics of the granular media. However, most previous studies have predominantly focused on idealized spherical particles, whereas real industrial materials often possess irregular morphology, resulting in more complex mechanical and thermal behavior compared to their spherical counterparts-a behavior that remains insufficiently understood. This doctoral thesis aims to fill this knowledge gap through a comprehensive experimental and numerical investigation of non-spherical particles in packed and moving bed configurations, with a particular focus on their flow dynamics and conductive heat transfer performance. This thesis provides a comprehensive framework for understanding the role of particle shape in granular packing, flow, and heat transfer in thermal energy storage systems. By integrating advanced experimental techniques, detailed shape analysis, and statistically calibrated numerical simulations, the work offers novel insights into the behavior of non-spherical particles in both static and dynamic systems. The findings emphasize the critical impact of particle geometry on packing structure, flow behavior, and heat transfer performance, offering practical guidelines for the selection and modeling of real granular materials in concentrated solar power and other energy storage applications.