Comparison of Heat Transfer in Gravity-Driven Granular Flow near Different Surfaces

Heat transfer in gravity-driven granular flow has been encountered in many industrial processes, such as waste heat recovery and concentrated solar power. To understand more about Moving Bed Heat Exchanger (MBHE) applied in this field, numerical simulation was carried out for the characteristics of granular flow near different surfaces through discrete element method (DEM). In this paper, both the performances of particles motion and heat transfer were investigated. It's found that, even though the macroscopic granular flow is similar to fluid, there is still obvious discrete nature partly. The fluctuations of parameters in granular flow are inevitable which is more obvious in the circular tube cases. A special phenomenon, where competition motion is found, is resulted from discrete nature of particles. In terms of heat transfer, overall heat transfer coefficients for plate are higher than that of tube owing to better contact between particles and wall. However, due to competition motion, particles in high temperature tend to contact the tube, which is beneficial to heat transfer in some local zones. The heat transfer characteristics above will also affect the temperature distribution near the outlet of different geometries.