Research on Heat Transfer Model of Asphalt Pavements Subjected to Microwave Heating Recycling

Abstract

In order to assess temperature field in microwave heating for recycling asphalt pavements, a 2D mathematic heat transfer model was developed based on Fourier heat transfer theory. The microwave internal heat-generation was researched by using surface field of pyramidal horn replacing approximate radiation field. In addition, the boundary conditions were built and normalization processing was implemented. The control volume based finite differential method (CV-BDM) was used to establish the implicit discrete scheme of the conservation equations, and the numerical value simulation was employed. By continuous or intermittent radiation heating technique, a microwave heating experimental system at 2 145 GHz was carried out to investigate temperature variation characteristics of asphalt pavements along with heating time. The result shows that (1) the increase of temperature of asphalt mixture during microwave heating is obviously nonlinear, the temperature rises slowly in the initial stage of the heating but increases rapidly in the late heating period; (2) the temperature distribution is non-uniform that the temperature in central area of the surface is higher while it is lower on edge; (3) the uniformity of temperature within asphalt mixtures can be improved by using intermittent heating technique, and the heating time must be reasonable. The simulation results are in preferable agreement with the experiment.