Experimental investigation of fine-grained settling slurry flow behaviour in inclined pipe sections

Abstract

For the safe and economical design and operation of freight pipelines it is necessary to know slurry flow behaviour in inclined pipe sections, which often form significant part of pipelines transporting solids. Fine-grained settling slurry was investigated on an experimental pipe loop of inner diameter D = 100 mm with the horizontal and inclined pipe sections for pipe slopes ranging from −45° to +45°. The slurry consisted of water and glass beads with a narrow particle size distribution and mean diameter d50 = 180 µm. The effect of pipe inclination, mean transport volumetric concentration, and slurry velocity on flow behaviour, pressure drops, deposition limit velocity, and concentration distribution was studied. The study revealed a stratified flow pattern of the studied slurry in inclined pipe sections. Frictional pressure drops in the ascending pipe were higher than that in the descending pipe, the difference decreased with increasing velocity and inclination. For inclination less than about 25° the effect of pipe inclinations on deposition limit velocity and local concentration distribution was not significant. For descending pipe section with inclinations over −25° no bed deposit was observed.

Concentration distribution and deposition limit of medium-coarse sand-water slurry in inclined pipe

“…As the slurry velocity decreased, the value of c v10, at first slowly and then rapidly, increased until the flow velocity V decreased to a value close to the deposition limit V D . Near the deposition limit, the local concentration c v10 suddenly increased and reached a value typical for the sliding or stationary bed (approximately c v10 ≈ 0.55-0.60), when a stable deposit was formed at velocities below V D (Matousek et al, 2019a;Vlasak et al, 2019a). The results of the radiometric method agree rather well with the visual observations; if the flow is steady and stable, the difference was less than 10%.…”

“…For velocities below the deposition limit, the stationary bed was observed in the ascending pipe for an inclination angle α < 30°. For descending flow, the thickness of the bed layer was significantly less, and the bed disappeared for pipe slope α < −15° (Vlasak et al, 2018a). Analogous behavior was observed for lower and higher transport concentrations, C v = 0.11 and 0.35 (see Figs.…”

“…6-8, the chord-averaged concentration profiles, c v (y), are illustrated for different pipe inclinations α and slurry velocities V close to deposition limit V D . The concentration profiles showed different degrees of stratification for the positive and negative pipe inclination (Krupicka and Matousek, 2014;Vlasak et al, 2016Vlasak et al, , 2017Vlasak et al, , 2018a. The degree of stratification varied with the pipe inclination, decreasing with increasing pipe inclination and slurry velocity for both the ascending and descending pipe sections.…”

“…The experimental investigation was carried out on an experimental pipe loop of inner diameter D = 100 mm with the horizontal (A), inclinable (B), and short vertical (C) pipe sections in the Institute of Hydrodynamics of the CAS in Prague (Vlasak et al, 2017(Vlasak et al, , 2019a. The loop was made from smooth, stainless steel pipes; its total length was 93 m, see Fig.…”

“…Matousek and Zrostlik (2018) dealt with the effect of the longitudinal component of the solids' weights in the bed layer and distinguished between contributions of contact solids, suspended solids, and those carrying liquid to the pressure drops in a partially stratified flow. Friction losses of the settling slurries' flows are strongly dependent on the concentration distribution; unfortunately, experimental data containing measured solid distributions, especially in vertical and inclined pipes, are extremely scarce in the literature (Matousek et al, 2019a;Vlasak et al, 2017Vlasak et al, , 2019a.…”