Coupling Discrete-Element Method and Computation Fluid Mechanics to Simulate Aggregates Heating in Asphalt Plants

Lowering production temperature in warm mix asphalt technology may lead to inadequate drying of aggregates, which results in moisture stripping of pavement. Because of the difficulty in direct observation of drying and heating aggregates inside the dryer, numerical analysis offers an alternative way to study heat transfer and aggregate temperature revolution. In this paper, coupled computational fluid dynamics (CFDs) and the discrete-element method (DEM) are used to simulate aggregate movement and heat transfer in a simple drum. The effects of aggregate size, drum rotation speed, flights, and fluid temperature on aggregate temperature evolution and heating efficiency are studied. The results show that a coupled CFD-DEM technique is an appropriate approach to study aggregate movement and temperature evolutions in the drum directly. Small particles can be heated more easily than large particles. Optimum drum rotation speed and inner flights could improve heating efficiency. In addition, higher fluid temperature could reduce the heating time of particles to reach a target mixing temperature. Preliminary results may provide useful guidelines for operating and designing the mixing drum efficiently. (C) 2014 American Society of Civil Engineers.