Effects of Operation Parameters on Heat Transfer in Tubular Moving Bed Heat Exchangers:A CFD-DEM Study

Tubular moving bed heat exchangers（MBHEs） present inherent advantages for efficiently and stably recovering sensible heat from high-temperature granular bulk.In this study,we introduce a viable and practical approach based on the combined approach of Computational Fluid Dynamics with Discrete Element Method（CFD-DEM） and employ it to conduct a comprehensive investigation into the effects of operation parameters on tubular MBHEs.These parameters include inlet particle temperature（ranging from 500℃ to 700℃）,tube wall temperature（ranging from 50℃ to 250℃）,and particle descent velocity（ranging from 0.5 mm/s to 12 mm/s）.Our analysis reveals that the heat radiation and gas film heat conduction predominantly govern the heat transfer process in the particle-fluid-wall system,collectively contributing to approximately 90% of the total heat flux of tube wall(Qwsimu).The results indicate that increasing the inlet particle temperature and reducing the tube wall temperature intensify heat transfer by enlarging the temperature difference.More interestingly,Qwsimu exhibits three distinct stages as particle descent velocity increases,including an ascent stage,a descent stage,and a stable stage.Furthermore,the simulation attempts suggest that the optimal descent velocity for maximizing Qwsimu falls within the range of 1.3-2.0 mm/s.These findings not only uncover the precise influence mechanisms of operation parameters on heat transfer outcomes but also offer valuable insights for heat transfer enhancement efficiency in MBHE system.