Investigation of flow and thermal non-equilibrium in a radially layered composite particle packed bed: flow-thermal non-equilibrium and radial layered composite

Abstract The radially layered composite particle packing structure has garnered considerable research attention due to its demonstrated potential in enhancing heat transfer and suppressing the wall effect. In this work, a combined Discrete Element Method and Computational Fluid Dynamics approach is adopted to systematically investigate the flow and thermal non-equilibrium characteristics in radially layered packed beds. The effects of key parameters, including inlet velocity and temperature, on the non-equilibrium performance are quantitatively evaluated using statistical indicators such as the mean value and root-mean-square. The results indicate that particle diameter and packing structure are key factors determining the radial flow and thermal non-equilibrium. The filling of smaller particles in the annular region effectively reduces the degree of radial flow and thermal non-equilibrium, whereas non-equilibrium fluctuations are intensified at the layered interfaces and within the high-porosity zones of the central region. Along the airflow direction, a significant thermal non-equilibrium is observed, as indicated by a bimodal distribution of the temperature root mean square. As the inlet velocity increases and the flow becomes fully developed, the temperature field becomes more uniform, thereby reducing the thermal non-equilibrium. Furthermore, an increase in inlet velocity exacerbates flow non-equilibrium. High temperature not only amplifies this effect but also extends the spatial extent of the non-equilibrium region.