A unified theory for gas–particle flow stress with particle friction and interstitial fluid effects

This article presents a unified theory that considers both particle friction and interstitial fluid effects for simulating gas–particle flow stress. For the first time, we proposed kinetic theory-based solid stress equations that can simultaneously take into consideration the interstitial fluid effect at low solid volume fraction and the friction effect at high solid volume fraction. A smooth transition between these regimes was realized using the inertial number model. We validated the theory with experimental data from a spouted bed and a riser and showed the advantages of our theory over some classical kinetic theory models (e.g., Lun, Agrawal, and GTSH model). The results show that the solid volume fraction at the riser inlet and the particle velocity in spouted beds are more accurately predicted by the new model. Furthermore, the influence of interstitial fluid effects on particle flow is more pronounced in the riser than in the spouted bed.