Experimental and numerical study of non-spherical particles in moving bed heat exchangers

Moving Bed Heat Exchangers (MBHE) are vital for high-temperature thermal management in applications like concentrated solar power and waste heat recovery. Although spherical particles are often used in MBHE research, industrial granular materials typically have complex, non-spherical shapes that significantly influence flow, packing, and heat transfer. This study investigates the flow behavior and heat transfer of non-spherical particles in a staggered tube MBHE, comparing with spherical particles. The first objective involves experimentally characterizing the flow of non-spherical and spherical bauxite particles around a tube using a particle tracking technique and subsequently validating a Discrete Element Method model. The second objective utilizes the validated model to analyze flow, heat transfer, and packing structure under varying outlet velocities. Non-spherical particles form broader stagnation zones, asymmetric sidewall flow, and narrower void zones, enhancing tube contact. Spherical particles create narrower stagnation and wider void zones with less contact. Cylindrical particles heat the tube faster and stabilize temperature earlier due to larger contact areas, while spherical particles heat slower with smaller contact areas. Furthermore, the packing structure at the tube surface was thoroughly analyzed for cylindrical particles for contact types classification. Higher outlet velocities enhance cylindrical particle alignment, thereby increasing the number of thermally favorable contact types as face–plane with larger contact areas. In contrast, spherical particles maintain more uniform but significantly small contact areas. Nonspherical particles significantly improve MBHE performance by enhancing flow behavior, particle–tube contact, and heat transfer efficiency, enabling more effective thermal management solutions in industrial applications.