Hydraulic transport in inclined large diameter pipelines

Abstract

Little is documented in literature regarding hydraulic processes in inclined and large diameter pipelines. The bulk of the previous research dates back 20 to 50 years and was done for small diameter pipelines of up to 150 mm.

This research focuses on gathering data and testing the existing models and ideas with regard to large diameter inclined pipelines and the hydraulic transport within them. The overall goals of the project are to gather knowledge on the less documented and studied principles of pipeline flows and validate ideas and
semi-empirical models from previous researches.

Extensive laboratory experiments were conducted as part of a joint research programme between Delft University of Technology and the National Engineering Research Center for dredging equipment and technology in Shanghai. The experiments were executed with a flow loop with a pipe diameter of 300 mm. It contains a measurement section of over 110 meters, part of which is inclinable. Pipe inclination angles of 17.9, 28.9 and 44 degrees were tested with slurry concentrations up to 15 % at flow velocities between 2 and 7 m/s. The flow velocities, delivered concentrations, total pressures, differential pressures and pump data were recorded. Conducting these experiments on this scale under controlled laboratory conditions is a unique research.

Three semi-empirical models by Worster and Denny, Gibert and Wilson for inclined slurry transport are validated. A comparison is made between ideas from literature regarding deposition limit velocities, delivered concentrations, pipe inclination angles, stratified flow regimes, particle suspension and different flow directions. The observations from previous researches with small pipe diameters are generally in line with the results of the experiments conducted for this thesis. The semi-empirical models prove to deliver accurate predictions of the total pressure gradients in heterogeneous flow regimes. With regard to stratified flows, it is proposed to modify the semi-empirical models by adding a factor to the suspension and solids effect terms. The factor is a function of deposition limit velocity, flow velocity, inclination angle and flow direction.