Numerical study of heat transfer for gravity-driven binary size particle flow around circular tube

Abstract

As the primary working medium in moving bed heat exchangers, solid bulk materials are composed of multiple size particles. To clarify the effect of particle size distribution (PSD) on heat transfer, the discrete element method (DEM) is used to study the flow and heat transfer of binary size particle flow around a circular tube. The heat transfer model for multiple size particles is developed and coupled with DEM method. The particle flow characteristics with PSD width are analyzed in detail. The results show that particle size segregation, competitive flow and flow instability are the unique characteristics of binary size particle flow around a tube. Wider PSD will enhance these characteristics and have a positive effect on particle renewal in the stagnation zone, which could decrease the local heat resistance. The total heat transfer coefficient between particle flow and tube wall increases at most by 9.73% as PSD is wider. • Binary size particle flow around a circular tube is studied with DEM method. • Binary size particle flow can form local particle size segregation around tube. • Binary size particles can decrease the stagnation zone above the tube. • A wider binary particle size distribution can increase the flow instability. • A wider binary particle size distribution can enhance heat transfer performance.