Abstract
Thermal management and heat transfer optimization remain central challenges in next-generation concentrated solar power (CSP) systems employing solid particles for thermal energy storage and heat transfer. Conventional particle receiver concepts, such as fluidized beds and falling particle curtains are constrained by limited particle-wall contact, flow instabilities, and restricted operating temperature. This work presents a combined computational and experimental investigation of a gravity-driven dense-phase moving packed bed receiver featuring a flat conduit geometry and sub-millimeter particles. A multiphase modeling framework is developed and validated against pressure-drop measurements and particle velocity data obtained from dedicated experimental setups. The validated model is subsequently used to quantify dense-flow stability and thermal performance under indirect heating conditions. Results demonstrate stable dense-phase operation with particle volume fractions of approximately 0.6, leading to enhanced particle-wall transfer. Alumina particles achieve wall-to-particle heat transfer coefficients of up to 2.7 kW·m-2·K-1, more than twice those obtained with silica sand under comparable conditions. The findings indicate that flat-conduit dense-phase receivers provide a mechanically simple and thermally efficient alternative to conventional particle receiver concepts, supporting high-temperature and more efficient CSP systems.