Pressure recovery characteristics for a dilute gas–particle suspension flowing vertically downward in a pipe with a sudden expansion: A two-fluid modeling approach

This work applies the Eulerian‒Eulerian model in conjunction with the kinetic theory of granular flow and inter-particle collisions to study the characteristics of pressure recovery for a dilute gas–particle suspension flowing through a pipe with a sudden expansion at a relatively higher solid loading. To do so, the numerical procedure was validated against experimental results for relatively small dilute phase flows in a pipe with a sudden expansion; a satisfactory agreement was obtained. Initially, the effect of the two significant numerical parameters namely, the speculairty coefficient and the coefficient of restitution for particle–particle collisions were investigated and then, for fixed combinations of these parameters the effect of particle-phase volume fraction, particle density, particle size, and inlet slip ratio were studied. It was concluded that pressure recovery diminishes as the speculairty coefficient increases and the particle–particle coefficient of restitution decreases. Pressure recovery was found to increase with increasing solid volume fraction for coarse particles whereas, for fine particles, a critical volume fraction is obtained above which pressure recovery reduces. An increase in slip ratio is found to diminish pressure recovery. Similarly, at relatively higher solid volume fractions, a critical diameter was found, above and below which pressure recovery decreases.