The behavior of particles in dilute phase pneumatic conveying is a rather complex phenomenon. For example, particle velocities and their trajectories owing to particle-particle and particle-wall collisions are unpredictable. In this study, we focus on particle velocity reduction in horizontal-vertical (H-V) and vertical-horizontal (V-H) bends. A new terminology, ‘bend point’ is introduced to compare different bends on common measures. A broad range of materials (Archimedes numbers = 10 2 to 10 6 ) was investigated using six different bends (blind-T, R/D = 1.5, 4.5, 6.6, 10, and 20) and wide range of conveying velocities (10 m/s < u a < 35 m/s). Small material quantities (ε ≈ 1) were fed at zero velocity through the flowing air stream in the pipeline (D = 50 mm). The particle velocities were measured along the axial direction. Visuals of the particle flow were recorded using a high-speed camera and analyzed by a Matlab program specially developed for this analysis. The experimental results demonstrate that materials must be conveyed in vertical pipes at higher than the terminal velocity, while the Reynolds and Archimedes numbers have a significant effect on the flow development. A new correlation of the bend point particle velocity ratio (BR) was developed based on the statistical velocity distribution of particles at different locations along the pipeline. The analysis of the results for both the H-V and V-H bends illustrates that the BR increases with the bend ratio (R/D), but after a certain limit, a further increase in the bend ratio causes a reduction in BR. This analysis will aid in the design of pneumatic conveying pipelines by selecting appropriate conveying criteria and proper bends at different orientations.
- Bend point
- Dilute phase
- Pneumatic conveying
- Vertical pipe, particle velocity