The existing numerical methods for modeling particulate flows can be divided primarily into three types: the resolved Eulerian–Lagrangian method or DNS, the unresolved Eulerian–Lagrangian method or discrete element method (DEM), and the Eulerian–Eulerian method or two-fluid model (TFM). Both the DNS and the DEM take the Lagrangian viewpoint by tracking particle dynamics while the carrying fluid is solved with Eulerian method. However, there is a significant difference between the DNS and the DEM in computing particle–fluid momentum and heat exchanges. For the DNS method, the flow fields, such as velocity, pressure, and temperature, are resolved around each particle based on the differential conservation of momentum and energy equations on a very fine grid; this allows the particle drag, lift, torque, and heat transfer rate to be computed directly from the resolved flow fields. The DEM, on the other hand, employs a much coarser grid, so the flow fields are not resolved; particle drag, lift, torque, and heat transfer rate have to be determined based on some empirical correlations. Compared to the DNS and the DEM, the TFM employs the Eulerian viewpoint for both solid particles and carrying fluid; it treats the large number of dispersed particles as another continuum “fluid” whose motion and temperature could be described by a set of partial differential equations derived from the laws of conservation.