CFD–DEM Investigation of Heat Transfer and Flow Characteristics in a Fluidized Bed Under Van Der Waals Forces Effects

Particle cohesion induced by van der Waals (VDW) forces can substantially affect the fluidization and heat-transfer behavior of fine polyethylene particles in gas–phase fluidized bed reactors, particularly under industrially relevant high temperature and high pressure. In this study, a computational fluid dynamics discrete-element method (CFD–DEM) model incorporating VDW forces and heat transfer is developed. This model is utilized to investigate particle-scale hydrodynamics and thermal behavior under high temperature and high pressure. Simulations with and without VDW forces are compared at inlet gas velocities of 0.012 and 0.020 m/s. The results show that VDW forces redistribute local gas volume fraction states and enhance particle connectivity, with elevated coordination numbers preferentially observed near the sidewalls and bottom corners. The influence of these interactions on particle transport becomes more evident at the higher gas velocity. VDW forces have a limited effect on the overall axial gas temperature distribution because the gas rapidly approaches the particle temperature near the inlet. In contrast, the influence on particle-gas convective heat transfer is more pronounced at an inlet gas velocity of 0.020 m/s, increasing the average heat-transfer coefficient by up to 6.12%. This study reveals the gas-velocity-dependent effects of cohesive forces caused by VDW forces on particle transport and heat transfer in polyethylene fluidized bed reactors.