Heat Transfer and Pressure Drop in Packed Beds of Crushed Rock Particles

Thermal energy storage using packed beds of crushed rocks finds application in solar thermal power generation, building thermal comfort, and greenhouse climate control. Crushed rock particles are irregular in shape and size, but notwithstanding have a clearly discerning long, intermediate, and short axis. Consequently, particles tend to pack down with their short axis facing upwards. As a result, the flow resistance and heat transfer characteristics in a packed bed depend on the flow direction relative to particle orientation. For small applications, the flow through a packed bed is typically one-dimensional, and one may rely on empirical correlations for design purposes. In this work, we propose that tortuosity is included in the heat transfer and pressure drop correlations. We derived our correlations from a combination of discrete element modeling (DEM) and computational fluid dynamics (CFD) and verified our results experimentally.