A parametric study for Euler-Granular model in dilute phase vertical pneumatic conveying

Abstract

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.

Proceedings of the 58th Conference on Simulation and Modelling (SIMS 58) Reykjavik, Iceland, September 25th – 27th, 2017

“…Because only the contraction walls hydraulic jumps were affected opposite to the flow direction, except the friction force. When the channel inclination angle was a negative value, the flow depth before the Venturi contraction reduced due to flow convert into the supercritical flow (Welahettige et al, 2017). At -1.0 degree angle, the flow depth increased in the Venturi region due to the oblique jump propagation (Welahettige et al, 2017).…”

“…Hydraulic jumps generate due to transition of the supercritical flow into the subcritical flow in an open Venturi channel (Welahettige et al, 2017). In a hydraulic jump, a strong shear layer is formed at the toe of the wave (Hornung et al, 1995).…”

“…This study focused on the flow depth variation in an open Venturi channel for Newtonian fluid. Computational fluid dynamics (CFD) simulations were validated with experimental results (Welahettige et al, 2017). ANSYS Fluent R16.2 commercial simulation tool was used for the simulations.…”

“…Simulations were done for water the flow rates: 100 kg/min, 200 kg/min, 300 kg/min, 400 kg/min and 700 kg/min. The experimental water flow rate result, which was equal to 400 kg/min, was used for the validation (Welahettige et al, 2017). The contraction region started at = 2.95 m (see Figure 1).…”

“…There were no barriers at the end of the channel and the channel expanded after the contraction. Therefore, flow condition was changed from subcritical to supercritical, when flow depth reduced at the end of the channel (Welahettige et al, 2017). In generally, the channel at horizontal angle gives subcritical flow before the contraction and supercritical flow after the contraction for all flow rates.…”