Minimum Transport Velocity of Gas-Solid Two-Phase Flow in a Pipe Bend.

Abstract

Studying the limiting gas velocity at which conveying is possible in a state in which particles are not stagnant on the wall of the pipe, called 'minimum transport velocity', is very important in terms of saving energy for transportation. However, relating to a pipe bend, concepts concerning the minimum transport velocity are few up to this time since the particle motions in the pipe bend are very complicated. From such viewpoints in this paper a basic model equation of the minimum velocity in the pipe bend is first introduced for the dilute phase flow in conventional pneumatic conveyance. Next, the minimum velocities are measured in an actual transport experiment for coarse particles. By analyzing the measured data, an unknown in the basic equation is determined and an empirical equation of the minimum velocity is provided. The experiments are carried out on the condition that the curvature radiuses of the right-angled bend from the horizontal to the vertical are 300, 500 and 700 mm, the pipe line is 10 m long and 50 mm in diameter, and the conveyed particle is Polyethylene pellet with particle diameter of 3.4 mm.