| Vertical pneumatic transport was investigated in a 0.026 m (1-inch) Plexiglas tube at various pressures. Nitrogen was the conveying gas at pressures of 101 kPa (0 psig), 790 kPa (100 psig), 2,170 kPa (300 psig), and 4,238 kPa (600 psig). Pressure drop, particle velocity, pressure fluctuations, and flow patterns were measured or visually observed and recorded. Choking velocity, velocity at minimum pressure drop, and the particle friction factor were also investigated at these elevated pressures. Glass beads (97 ;Investigation of the friction factors for the small particles (89 ;Pressure fluctuations were analyzed in the frequency, amplitude, and time domain. This was done to match characteristics of the analysis to the flow patterns of the gas-solid flow. Power spectral density functions and probability density functions exhibit particular characteristics at different flow patterns in the system.;The Zenz type diagram of pressure drop per unit length versus gas velocity was found at all pressures investigated. As pressure increased, the curve shifted up and to the left. Gas velocity at minimum pressure drop thereby decreases as the pressure increases. The same trend is observed for the choking velocity. Average particle velocity of the gas-solid flow mixture tends toward the gas velocity at higher pressures faster than it does at lower pressures. |
