Abstract
Particle settlement and pressure drop in a gas–solid two-phase flow in a pipe with a circular cross-section are studied at mixture inlet velocities (V) ranging from 1 m/s to 30 m/s, particle volume concentrations (αs) ranging from 1% to 20%, particle mass flows (ms) ranging from 5 t/h to 25 t/h, and particle diameters (dp) ranging from 50 μm to 1000 μm. The momentum equations are based on a two-fluid model and are solved numerically. Some results are validated through comparison with the experimental results. The results showed that the gas and particle velocity distributions are asymmetrical around the center of the pipe and that the maximum velocity point moves up. The distance between the radial position of the maximum velocity and the center line for the gas is larger than that for the particles. The particle motion lags behind that of the gas flow. The particle settlement phenomenon is more serious, and the particle distribution on the cross-section is more inhomogeneous as the V, αs, and ms decrease and as dp increases. It can be divided into three areas according to the pressure changes along the flow direction, and the distinction between the three areas is more obvious as the αs increases. The pressure drop per unit length increases as the V, αs and ms increases and as dp decreases, Finally, the expressions of the settlement index and pressure drop per unit length as functions of V, αs, ms, and dp are derived based on the numerical data.
Highlights
Particle transport through a pipe is quite common in the power generation, metallurgy, machinery manufacturing, pharmaceutical and food production, and material engineering industries, among others
The pressure distributions along the flow direction for different particle volume concentrations are shown in Figure 4, where the pressure values are relative to the atmospheric pressure at the pipe outlet
The pressure decreases approximately linearly as the pipe length increases in the fully developed area (0.8 ≤ z/L ≤ 1) where the pressure drop per unit length is a constant that increases as the particle volume concentration increases
Summary
Particle transport through a pipe is quite common in the power generation, metallurgy, machinery manufacturing, pharmaceutical and food production, and material engineering industries, among others. Some research has already been published on particle settlement and pressure drops in gas–solid two-phase flow in a pipe. Chiodi [8] indicated that the transport of dense particles depended on the ratio of the shear velocity of the flow to the settling velocity of the particles and the Reynold’s number of the sedimentation. There have been some studies on particle settlement and pressure drop in gas–solid two-phase flow, few studied both at the same time. In the present study, the momentum equations based on a two-fluid model are solved numerically, and the distributions of velocity and particle concentration as well as pressure drop are analyzed. The effects of inlet velocity, particle volume concentration, particle mass flow, and particle diameter on particle settlement and pressure drop are discussed. The relationship between the settlement index, pressure drop, and related synthetic parameters is determined based on the numerical data
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