A PARAMETRIC STUDY FOR EULER-GRANULAR MODEL IN DILUTE PHASE VERTICAL PNEUMATIC CONVEYING

摘要

The Euler-Granular approach was used to predict pneumatic conveying characteristics of vertically upward dilute phase flow. Three-dimensional computational fluid dynamics simulations were carried out for 8 m long and 30.5 mm diameter circular pipe. The density of conveyed materials was 1020 kgm~(-3). Simulations for different particle diameters: 200 μm, 500 μm and 3 mm were performed. The air velocities ranged from 7 to 16 ms~(-1) and solid to air mass flow ratios ranged from 1.2 to 3.6. The main objective of this study was to analyse the sensitivity of specularity coefficient in Johnson and Jackson particle-wall boundary conditions on conveying characteristics. It was found that there is a significant sensitivity of certain ranges of specularity coefficients on pressure drop, air and particle velocities and solid distribution in pipe cross section. Among the tested range of the specularity coefficient values, some values are recommended for different particle sizes by comparing the predicted results with experimental data from existing literature. Moreover, it was also found that the coefficient of restitution for particle-wall collisions which counts the momentum loss by the walls in normal direction has less sensitivity on the results compared to that of specularity coefficient which counts the momentum loss by the walls in tangential direction.