Numerical Study on Flow and Heat Transfer Characteristics in Spherical Particle Packed Beds Under Unheated and Heated Conditions

The Discrete Element Method is employed to simulate the free-falling packing process of spherical particles and construct a three-dimensional random packing model. Additionally, parametric geometric modeling is subsequently applied to establish two ordered packing models (in-line and staggered arrangements) for comparison. After model validation, pore-scale simulation is performed to examine the flow and heat transfer characteristics under both unheated and heated conditions in the three packed beds. The simulation accuracy is systematically verified through comprehensive analysis of both pressure drop and temperature distribution profiles. The results demonstrate that both operating conditions and packing configurations significantly influence the flow and heat transfer characteristics. Under unheated conditions, the pressure drop and average velocity increase markedly compared to heated conditions, with the pressure drop rising approximately threefold and the peak average velocity increasing by about 3.5 times. Furthermore, higher inlet velocities amplify the gas-solid temperature difference, resulting in more pronounced gas-phase temperature fluctuations-a phenomenon particularly evident in the in-line and staggered packing structures. In contrast, the random packing promotes more uniform flow and heat distribution.