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°C to 700°C), tube wall temperature (ranging from 50°C to 250°C), 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 (Q _w ^simu ). 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, Q _w ^simu 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 Q _w ^simu 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.